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close this bookPrimary School Agriculture Volume II: Background Information (GTZ, 1985, 190 p.)
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(introduction...)

Herbert Bergmann/ Richard Butler

A Publication of the Deutsches Zentrum fwicklungstechnologien - GATE , a Division of the Deutsche Gesellschaft fhnische Zusammenarbeit (GTZ) GmbH - 1985

Preface

This volume II of the manual on "Primary School Agriculture" provides factual information on questions which may arise when teaching agriculture. It should only be used together with volume I, Pedagogy. It consists of three parts:

- Farming Methods,
- Crops,
- Crop Storage.

Part one, Farming Methods, is intended as a documentation on various agricultural methods. In the first section, the objectives are discussed, i.e. why pupils should learn about farming methods and what results are to be achieved.

This is followed by information about traditional farming, covering such topics as clearing and tilling, planting and sowing, weeding and tending, and, most important of all, multiple cropping and crop rotation. Teachers will find ample information about these aspects of traditional farming. Thus, it should be easy for them to study farming activities near the school and to contrast them with distant regions.

The section on traditional agriculture ends with a number of observation questionnaires and survey instruments to guide teachers in outdoor observational activities concerning traditional farming.

The next section deals with Agriculture. It compares modern agriculture as practised in the industrialized countries with the Scientific Agriculture advanced in the subject of-"Rural Sciences" and with traditional agriculture.

The last section outlines recent developments in tropical agriculture, showing that there is a general tendency to encourage a new and unbiased approach to traditional African farming. Some of the most interesting research results in this area have been summarized; the section ends with suggestions on how to experiment with this new approach in school.

Part two, entitled Crops, should be used when a teacher needs information about the crops to be grown on the farm. Twelve crops are treated in a standard manner with illustrations of each of them. The main topics covered on the individual crops are:

- the plant,
- origin,
- farming the crop,
- processing.

It provides general information on the range of yields per hectare, showing how much crop yields can vary according to natural conditions and tending.

Finally, there is an analytic table of English vocabulary relating to the main crops.

Part three treats Crop Storage. Again, it gives an account of traditional and simple, modern methods of storage and pest control. The language level is such that the teachers may use it as reading material in the final classes. Its many illustrations enhance the information contained in the text.

Parts I and II were written by Herbert Bergmann, while part III was written by Richard Butler.
This manual could not have been written without the help of many people who cannot all be named here.

Special thanks are due to the Government of the United Republic of Cameroon who made my stay in their beautiful country possible, and to the Cameroonian educational authorities who supported IPAR research and pilot project work in Environmental Studies with patience, sound advice, and invaluable administrative assistance, as well as to the German Agency for Technical Cooperation which agreed to fund this follow-up work to the project.

I am greatly indebted to Mr. V.J. Divine, a member of the senior staff at IPAR-Buea, who taught me a great deal about Cameroonian agriculture and Rural Science, and who gracefully submitted himself to the rigours of extensive field research.

I would also like to mention the contributions of those Cameroonian teachers, colleagues, and friends who participated in the IPAR-Buea school farm scheme and attended the respective seminars. Their contributions in the form of written material and discussion have helped to make the manual what it is.

I am equally grateful to Mr. R. Butler for his readiness to place his expert knowledge on crop storage at the disposal of teachers and pupils. Miss P. Smithson's and Miss Germann's art work deserves special mention; it facilitates the reading and complements a large part of the text.

I would also like to express my gratitude to Dr. and Mrs. Greenland who edited the manuals as far as language is concerned and, last but not least, to Mrs. H. Winkler who never lost spirit in what sometimes was a very tedious job typing and correcting the manuscript.

Herbert Bergmann

1. Objectives

Farming is an art which has developed slowly over centuries of human existence. It is based on very long experience and continuously adjusts to changing conditions. Every people, every group have their own way of going about farming, and individual farming women and men often have their own special skills. It is with these ways or methods of farming that the following section is concerned. Terms used in this connection are farming methods, farming techniques, and land-use systems to denote a whole combination of methods and techniques. One of the general aims of primary school agriculture is to prepare the way for improved farming in order to raise agricultural production or to reduce the work-load of the farming women and men. Teachers therefore need a fair knowledge of the most important techniques suitable for different environments.

We shall start this section with some information about traditional farming methods. Significant agricultural progress may be possible by improving traditional farming methods. Progress might also require something entirely new, a break with tradition. In both cases, however, it is necessary to know what is happening at present and why things are as they are.

"Before any consideration can be given to possible developments on African small-holdings and the means by which these can be brought about, it must be determined what farmers are now doing, what factors govern their actions, and what pressures there are to change the pattern of agriculture that results." (Cleave, J.H. 1974, p. 31).

There are several good reasons for carefully examining traditional farming methods:

- Traditional land-use systems are adjusted to local conditions in the best possible way under prevailing circumstances since they are the outcome of centuries of learning.
- A lot of experience based on long observation and practice has accumulated which should be made available to as many people as possible.

- The inferiority of traditional agriculture is by no means established. There are sound reasons for mixed cropping, and there are local systems of crop rotation and crop sequences that have proved their value.

- Farming techniques are as much part of a people's culture as are its religion, its language, its history, and its arts.

- Therefore, traditional farming is embedded in a way of looking at the world and life in general. Ideas about cause and effect governing traditional farm operations will inevitably be applied to new, "modern" techniques. In order to take them into account it is necessary to know them. If, for example, people believe that fertility can be stolen from a farm by means of magic this might influence their outlook on organic and chemical fertilizers.

After this we shall briefly examine so-called modern or scientific agriculture which is still prescribed in current Rural Science syllabuses. Part I will end with some information about recent developments in research on tropical agriculture. These developments seem to agree much more with traditional African agriculture than the approach to modernizing agriculture favoured so far.

A number of major objectives can be pursued in teaching about farming methods. The following list spells out a few of them:

1. Pupils will acquire basic knowledge and skills concerning farming techniques.

2. Pupils will systematically acquire basic knowledge about traditional farming techniques in their area and in other parts of the country.
3. Pupils will develop pride in African tradition by discovering the advantages of traditional farming methods.

4. Pupils will be able to assess critically different farming methods.

5. Pupils will learn the logic and skills of observation and experimentation in an elementary form by comparing traditional and nontraditional methods of farming the same crop(s).
6. Pupils will develop at an elementary level the capacity to select farming methods adapted to local conditions.

7. By dealing with traditional agriculture and the body of knowledge and beliefs supporting it, schools will be able to document local knowledge about crops, farming techniques, soil and other related topics that up to now have only been handed down orally.

8. Teaching about farming methods may lead to links with the extension service and nearby agricultural research institutions. The school will receive up-to-date information on research findings and in turn will provide the extension service and research institutions with feed-back on the local relevance of their proposals and findings.

The last two objectives are beyond the reach of the usual classroom but are intimately linked with generating new knowledge and making such knowledge available. Pursuing them will certainly enhance the effectiveness of classroom teaching and school farm work.

Farming is a complex art which has developed over centuries, based on long experience and continuously adjusted to changing conditions.
One of the general aims of primary school agriculture is to prepare the way for improved farming to raise agricultural production and to reduce the work-load of farmers.
Learning basic knowledge and skills concerning traditional farming-methods pupils will develop pride in African farming techniques.

By learning about new land use systems which are based on the work of agricultural research institutions, and by comparing them with traditional ways of farming, pupils will develop a better knowledge of farming methods.

Teachers need a good knowledge of important agricultural techniques suitable for different environments.

2.1 Traditional land use systems from shifting cultivation to degraded bush fallow

In many parts of Africa there are four types of traditional land-use systems:

1. shifting cultivation,
2. rotational bush fallow,
3. grass fallow, and
4. continuous cultivation.

1. Shifting cultivation is a system where a few years of cultivation are followed by very long fallow periods. Fallowing is so long that trees and bushes can grow up again to form a secondary forest. In this way, fertility is completely restored to the soil after it has been farmed. But it means that fallow periods must be longer than ten years. Less than ten per cent of a community's land could therefore be farmed at any one time.

2. As fallow periods have become shorter, shifting cultivation has given way to rotational bush fallowing. Here, too, the time that the land lies fallow exceeds the time the land is under cultivation. Provided the fallowing period is long enough, bush fallowing also restores soil fertility:

". . . when the time period between each cycle of cutting and burning was always in excess of seven years . . . the Bush Fallow developed as a stable ecological systems." (Obi, J.K., and Tuley, P., 1973, p. 1)

"It can be seen that Bush Fallowing has many merits in the preservation of soil fertility. The soil is exposed for a minimum period of time by mixed cropping, the root system of the fallow is largely left intact, the fallow recovers quickly . . ." (Obi, J.K., and Tuley, P., 1973, p. 5)

"The stability of the system depends on the number of years that the land remains under fallow. NWOSU mentioned a 'basic rotation' with a fallow period of seven years: 1st year: yams, early maize and vegetable, cassava; 2nd year: cassava followed by bush fallow; 3rd - 9th year: bush fallow" (Lagemann, J., 1977,p.9).

3. With further shortening of the fallow periods, the land-use system develops into a degraded bush fallow system. Fallow periods are too short to fully restore soil fertility.

When the fallow period is reduced to just one or two years, shrubs and bushes no longer grow again after farming but are replaced by spear grass. The bush fallow system turns into a grass fallow system.

4. On the compounds, immediately surrounding the houses, there is continuous farming. The compound area is fertilized with a variety of materials, e.g. household refuse, animal droppings, grass and twigs for mulching. Fertility here is very high and is conscientiously maintained.

"Compound farming is not a special land use system found only in Eastern Nigeria; it can be found world-wide in tropical regions where land scarcity has forced farmers to intensify production on small fields." (Lagemann, J., 1977, p. 30)

"Compound farming is . . . a type of land use which is of general importance in the humid tropics." (Lagemann, J., 1977, p. 31)

The following table shows the frequency with which the different land-use systems occured in a survey of about 200 farmers in Cameroon (compound farms excluded).

Fallowing

Length of

Land Use System

1 year

7.6%

grass fallow

2 years

28.8%

grass fallow

3 years

30.3%

degraded bush fallow

4 years

4.4%

degraded bush fallow

5 years

6.1%

degraded bush fallow

6 years

3.0%

degraded bush fallow

7-8 years

7.6%

bush fallow

9-10 years

4.5%

bush fallow

more than 10 years

7.6%

shifting cultivation

The areas with long bush fallow or shifting cultivation are remote areas with plenty of unoccupied land. By and large, periods of fallowing are tending to grow shorter whereas periods of continuous cropping remain the same or become even longer.

The length of the farming and the fallowing period is not left open to the choice of the local farmers but is the result of differences in local conditions. This is borne out by the way the length of the fallow period is affected by the general level of development of a community. The fallow period becomes increasingly shorter as one moves from isolated areas into urban or semi-urban communities. As food-crop farming becomes more market-oriented, fallowing periods get shorter.

In order to understand clearly the importance of fallowing in traditional agriculture, let us look at the graph 1. It takes the percentage of available nitrogen in the soil as an indicator of soil fertility. Three years of farming are followed by five years of fallowing. After the nitrogen content has reached its lowest level under maize cultivation in the second year, it increases after the cultivation of nitrogen fixing groundnuts. It rises steeply during the fallow period, but most of it is used up by yam farming in the first year after the fallow.


Graph 1: Development of Nitrogen in the Soil in the Traditional Rotation of the Baoule, Ivory Coast (adapted from Cadillon, M., undated)

How dramatically the length of the fallowing period can affect yields may again best be seen from graph below. It portrays the relation between yields as measured in dry matter per hectare and the number of years a plot is left fallow. It is taken from an area with light or sandy soils in Eastern Nigeria; the author of the study thinks, however, that the effect of lengthening the fallow period would be less pronounced in heavy or clay soils.

Further statistical analysis showed that 60 per cent of the increase or decrease in yields was most probably due to changes in the fallow periods.

Shortening fallow periods are a sure sign of pressure on land. As the fallow periods shorten, soil fertility is restored only imperfectly: "The length of the fallow cycle depends upon the fertility of the soil and the availability of land. Where land is scarce the fallow cycle is short, and as population density increases fallow cycles . . . become increasingly shorter .... the abbreviated fallow cycles result in the steady depletion of soil fertility and a continuous decline in crop yields." (Smock and Smock, 1972, p. 73)


Graph 2: Relationship between Output of Crops and Length of Fallow Period Prior to Cultivation (source: Lagemann J., 1977, Fig. 15, p. 67)

· This means that schools and the agricultural extension service alike should stress the maintenance of soil fertility through fertilizers, manuring, and erosion control especially when they are operating in better developed and densely populated areas.

2.2 Traditional Farming Methods

Traditional farming is characterized by

- the use of fire for clearing a new farm plot (slash-and-burn agriculture),
- superficial tillage by hand,
- often planting on mounds or ridges,
- mixed cropping using a number of carefully composed crop associations,
- the lack of any inputs for fertilizing and crop protection.


2.2.1 Clearing

Especially clearing by fire has been heavily attacked for destroying the soil. Here, in less technical terms, are the advantages and disadvantages of burning:

"Burning of the bush has the following advantages:

- It kills most grasses and weeds, so that the first weeding needs to be done relatively late. The alkaline ash raises the pH and availability of cations in the surface soil.
- Nutrients like P, K and Ca are made available in soluble form, which stimulates the growth of plants during the early growing, period.

On the other hand there are some disadvantages inherent in the system:

- The carbon, nitrogen and sulphur in the fallow and litter are lost in the burn (but not the amounts in the soil humus).

- The fire damages trees like oil palms, raffia palms, etc.
- There is a build-up of fire-tolerant, low-productive species.

Burning is, however, still an indispensable part of the system. Crops in bush fallow rotations depend on the pH effect of the burn, and in grass fallow systems the burning of the grass is still considered to be more advantageous than composting - in particular in terms of return on labour." (Lagemann, J., 1977, p. 48/49)

Clearing in the Forest Zone

Burning of grass and undergrowth is very common, even more so the burning of the taller trees. In most cases, the dead trees are left standing on the farms, though sometimes the trees are allowed to continue growing as they are used for shade.

We may distinguish between the following systems of bush clearing in the forest zones:

- Burning of the grass and trees.
- Use of grass and undergrowth as manure, burning off the trees.
- Use of grass and undergrowth as manure and felling of the trees for timber or firewood.

Clearing in the Grassland Area

In the grassland areas, we have identified four distinct methods of farm clearing:

- Burning of grass and shrubs.
- Burning according to the nkara-system.
- Covering the grass with soil for green manure.
- Leaving the grass on top of the soil for manure.

The nkara-system consists of cutting the grass down, covering it with soil to form a ridge, and then burning the grass. This keeps all the ash in the soil and makes a slow burning fire. It is on nkara ridges that egusi melons and Irish potatoes would be grown in the first year after clearing. There is a variant of nkara which consists of making ridges immediately after burning so that little of the ash is lost. But this is not as effective as the nkara system since the fire burns much faster, and the greater amount of smoke takes away more of the ash particles.

Farmers know that burning was strongly discouraged by the Department of Agriculture. They gave specific reasons why they continued it, or under what conditions they used fire for clearing:

- to kill off roots and stumps of trees and shrubs,
- to grow groundnuts - they do very well immediately after burning,
- to grow egusi melons,
- to grow cocoyams.


2.2.2 Tilling

In the overwhelming majority of cases tilling is done by hand. A hoe with a large blade is the universal tool for tilling. So far, only in some areas are ox-drawn ploughs used. But there are plans to extend this method of tilling to other parts of the country where the slopes are gentle. Deep ploughing as done in Europe would be disastrous in tropical conditions since it would aggravate soil erosion.

There are several traditional methods of tilling. The simplest one, practiced on fertile, well drained soil, is the simple scratching of the surface with a cutlass, planting maize seeds and covering them at once with soil. Tilling and planting are done at the same time. According to the slope of the land, the farmers often make mounds or ridges when tilling. These ridges, mounds or beds often contain grass and the remains of the previous crops as manure. Initially, ridges were made down the slope of a hill. In this way, work was easier for the women who worked moving uphill. Contour ridging means a much more uncomfortable working position, the more so the steeper the slope. The downward sloping ridges make erosion worse.

2.2.3 Timing - The Crop Calendar

The correct timing of farm operations is part of good farm management. Timing is particularly important with respect to planting, weeding, and, for some crops, harvesting.

The right planting time is a matter of great concern in traditional agriculture. It is so important that certain ethnic communities in Africa follow a religious ritual in determining the right time for planting. After consulting an oracle, a dignitary, often a woman, sometimes the chief of the area, will anounce the start of the planting season. In fact, since germination and healthy plant growth very much depend on the availability and distribution of rainfall, a good deal of familiarity with the local climate is needed in order to be able to choose the best time for planting.

Research findings on planting times can again be drawn from the study "Traditional African Farming System in Eastern Nigeria":

"Time of planting is significantly related to the output on compounds as well as on outer fields in all three villages. There is statistical evidence that supports farmers' experience that late planting reduces the yield of their crops. The data suggest that farmers who planted their crops later than others suffered a worse labour bottleneck during planting time . . ." (Lagemann, J., 1977, p. 70)

". . . other things being equal - later planting reduces the aggregate production of arable crops". (Lagemann, J., 1977, p. 73)

The effect of weeding on plant development also depends on good timing. In traditional agriculture, weeding may be done later than in modern agriculture, due to the effect of fire on weeds:

". . . early weed growth after the burn was minimal, and as most farmers only weeded once, the one weeding gave superior results if performed later than very close to planting, when weed competition was minimal." (Lagemann, J., 1977, p. 74)

Although this result was obtained from a study on maize farming, similar results have been obtained for arable crops in general. If weeding is carried out more than two months after planting, yields decrease in proportion to the length of the delay in weeding.

The importance of good timing in traditional agriculture can be seen in the fact that mutual help is most prominent when the time factor is important. The institutions of mutual help, e.g. the work groups of men and women, are organized for farm clearing and - in order to get the farm ready in time - but also for planting and sometimes weeding.

Information about timing is summarized in the crop calendar. A crop calendar shows how farm work spreads throughout the year for each crop that is included. The crop calendar proposed here (p. 24/25) shows the major annual and perennial crops grown. It is subdivided into two calendars, one for the lowland zone, and one for the highland zone. The crop calendar tends to show the "best" times for each activity.

Reading the Crop Calendar

For easy comparison, all farm work has been grouped into four main operations: soil preparation, planting, farm maintenance, and harvesting Any teacher is free to break these operations down into their component parts. For example, soil preparation in maize farming may consist of cutting down grass, burning, tilling, and ridging.

The crop calendar which is being used as an example refers to a central african country between 4° and 6° north of the equator.

Taking the example of maize, this is the information contained in the crop calendar of the rain forest zone:

- Farm preparation (clearing, tilling) starts in January and will be finished by the end of February.
- Depending on the first rains, planting may be done between late February and early April, mostly around mid-March.
- Farm care (weeding and thinning) starts in mid-April and may go on until the middle of June.
- Harvesting depends on planting time and the length of the life cycle of the varieties used. It starts as early as the beginning of June and may end only by the end of July.
- In areas with very early planting, tilling for a second maize crop has already started by the beginning of July.

- Planting starts in August and ends by the end of September.

- Since the second crop is planted during rainy season, weed growth starts earlier. Therefore, weeding is done earlier after planting than is the case with dry season maize crop.

- Harvesting spreads over November and December, again due to differences in planting time.

The crop calendars do not show a time for farm preparation for crops like beans, groundnuts, egusi and Irish potatoes. This is because most of the time they are intercropped with major staple food crops such as maize and yams. Therefore their time of farm preparation is the same as for the main staple food crop they are combined with.

For the annual crops, all the farming operations occur in a yearly cycle. For some staple foods - cassava, some varieties of yams, cocoyams and colocasia - this cycle is longer than one year but once it is finished, the whole sequence with all the operations will have to start afresh.

The cycle is different with tree crops. Farm preparation is done only once during the lifetime of a coffee, cocoa, or oil-palm tree. The plot will have to be prepared for transplanting the seedlings. Once the tree farm is established, the annual activities are farm care - weeding, pruning, mulching, application of fertilizer -, and harvesting. Processing of the harvest - drying, fermentation, de-pulping, oil making, safe storage, transportation and marketing - are much more important than for the annual crops but are not shown on the calendar.

Using the Crop Calendar

a) Selecting crops for school farm work

The crop calendar can be useful in selecting crops for the school farm. When checking crops against term time and holiday periods, four questions must be answered:

- Is there enough time for harvesting, drying, and storage? If not, what can be done to ensure that these operations are done in time, especially during the summer holidays?

- What important farm work tasks fall in holiday periods?

- Is the vegetative cycle of a given crop longer than 9 months (one academic year) or even longer than 12 months (this is the case when harvesting is shown in the same month or a few month later - mostly in the case of root and tuber crops)?

If any such crops are grown, or if perennial food crops like pineapples are farmed, they should be farmed early enough for the class which planted them to harvest the whole crop. Thus, pineapples should be farmed as soon as a class starts farming, cassava, cocoyams and cococasia should be farmed in class 5, so that at least by the end of class 6 the crop can be harvested.

Annual food crops must be preferred since they limit farm planning to periods of one year.

The main planting season for plantains and bananas is the rainy season. Schools could also very well establish coffee, cocoa, and oil palm nurseries which could be prepared in February and started in March. The seedlings could be sold at transplanting time.

A simplified version of the crop calendar should be prepared for teaching in the lower classes. This may be done by concentrating on one crop only or on the two or three crops being grown on the same plot, e.g. maize, beans, and okro. Simplification could also be achieved by concentrating on one activity, e.g. harvesting, for a number of important crops. This would show the availability of various crops throughout the year. An example from Nigeria is provided in the figure below.


Time Sequence of Harvest and Availability of Major Annual Staples in Eastern Nigeria (adapted from Lagemann J.,Fig. 6)


Crop Calendar of the Rain Forest Area


Crop Calendar of the Grassland Savannah

b) Lesson topics - Finding out the crop calendar of the school community

Taking the appropriate crop calendar as a reference, the class can be asked to work out the calendar of farm operations for the crops to be farmed on the school farm. Groups of children can be asked to find out from their mothers the locally agreed timing for the various farm operations. This can then be checked against the information provided by the general crop calendar. As the year goes by, observations made on the school farm and on local farms will add precision to the first draft based on questions asked.

- Breaking the main farm operations down into their component parts

This is an exercise in further precision and might be useful in final year language teaching as well as in teaching on agriculture. In defining the different activities that make up farm preparation or farm care, one might refine the calendar for the crops selected.

- Concentrating on harvesting periods would give an approach to market studies. Price fluctuation for different foodstuffs could be studied in terms of harvesting periods.

- Harvesting periods can equally well be used to discuss the changing composition of meals throughout the year in different regions. This can be done particularly well if from the crop calendar a calendar is derived which shows the availability of the main food crops throughout the year, and which adds the harvest times for the various fruits, and the main fishing and hunting season. This leads to a complete picture of the nutritional situation.

- In a social studies teaching unit on work organisation, the distribution of work loads for men and women in a typical forest area or grassland area farm household can be analysed.
- Similarly, one can also speculate about food requirements, taking into account how heavy the work load is at different times of the year.

These are only a few suggestions. We shall depend on the creativity and resilience of the teachers to make full use of the possibilities which the crop calendar offers.

2.2.4 Planting and Sowing

Work connected with planting and sowing differs very much according to the crops grown. We shall therefore make a few general observations about planting in traditional farming. Much of the detail will be left to the sections on particular crops.

- Selection and preparation of seed material Selection of seeds, tubers, corms, suckers or cuttings as planting material always involves a lot of skill and careful observation. Each farming community has its set of rules in order to find out what will make the best planting material. Pupils could be asked to find out from their mothers and fathers how they recognize suitable planting material and what signs they look for when they reject a plantain sucker or a groundnut seed for planting. There are also a number of techniques of safe storage and of preparation of seed material for planting. One such technique is pre-germination (maize and bean seeds, seed yams) which advances plant growth after planting. These techniques should be described and discussed in school.

- Actual planting

Crops are always planted by digging a hole and burying the seed material in the soil. Unlike in earlier European farming, cereals are not broadcast but the individual seed grains are planted one by one.

Some crops are planted together at the same time under the method of mixed cropping. Thus, maize and bean seeds or groundnut seeds may even be mixed in the same container used for planting. There are never less than three maize seeds put in a stand, often more, and the same number of bean or groundnut seeds. If cocoyam or colocasia are interplanted with maize, this is done when the maize has already germinated and the plants are well established. This has the advantage, among other things, that patches of ground can be used where the maize seeds failed to germinate.

Planting is not done in straight lines, nor according to precisely measured distances. Since neither animal drawn implements nor engine-powered machines are used at any stage during farming, there is not really a need for straight lines. All that is required is that enough space is left for people to pass when they weed or harvest without damaging the crop.
On a mound farmed with maize, beans, and leaf vegetables according to traditional methods, the average distance between stands was roughly 40 cm, with a standard deviation of 15.7 cm. This certainly does not represent a strict standard of planting distances. But as can be seen from the table, most stands are between 25 cm and 55 cm apart from each other.


Mound Planted with Maize and Beans (seen from above)


Mound Planted with Maize and Beans (side elevation)


Distribution of Crops on a Manual (adapted from Okigbo and Greenland, 1979, p. 74)


Planting Pattern in a Sahel Region (adapted from Okigbo and Greenland, 1979, p. 84)

Distance between stands (in cm)

Frequency absolute

In per cent

9-15

5

17.9

24-35

3

10.7

40-49

11

39.3

50-55

6

21.4

56 and above

3

10.7


28

100.0

On the mounds, crop density is high and amounts to 6 - 7 stands per square meter. Making allowance for the paths between the mounds that use up quite a lot of land, this would amount to about 45 000 stands with at least two plants each per hectare. The study from Eastern Nigeria reports crop densities of 22 000 to 31 800 stands per hectare on compound farms immediately surrounding the house, and between 12 000 and 40000 stands on farms away from the compound (Lagemann, J., 1977, pp 36 and 45)

On very fertile soil, the following densities were recorded, using the density square:

- 14 400 stands of maize per hectare in mixed cropping on the flat,
- 39 000 stands of maize and beans in mixed cropping on mounds,
- 12 000 stands of maize per hectare in mixed cropping on mounds.

Crop density varies a lot according to soil fertility, the crops grown, and the amount of preparatory work a farmer is willing to do. Well prepared soil will support a higher crop density than poorly tilled soil.

When ridges are formed, as is normally the case across the slopes of hills, more or less continuous contour lines are formed. Ridges are of rather uniform width, depending on the work habits of the woman building them.

Planting on ridges is often done in staggered rows. For example, up to three rows of maize and beans or groundnuts or cowpeas may be planted on a ridge. Again, planting distances are not measured out by a yardstick, but they are not haphazard either. They follow rule-of-thumb knowledge about the best density on a given soil. If a school class went to measure the distances between stands of maize or cocoyams along one or two ridges planted according to traditional methods the children might be surprised by the degree of regularity they found.

The illustrations in this section show how one might represent graphically the planting patterns used on mounds in traditional farming. Similar patterns may be used for ridges.

2.2.5 Weeding

Weeding is a feature of nearly all farming. Exceptions are farms where crop associations are found which keep down most or all the weeds so that weeding becomes unnecessary. This is the case where pumpkins or various species of melons are grown as a secondary crop.

Weeding is usually done with a hoe. Weeds are left on the farm to wither - except those that could immediately start to grow again. As they decompose, they add nutrients to the top soil. If they are available in sufficient quantities they act as mulch, protecting the top soil against erosion and loss of water. Weeding is very demanding in terms of labour. If it is done too late there will be serious damage to crop yields (see the section on timing of farm operations above).

The following is an example of the effect of late weeding on maize growth:

On a local farm with maize and cocoyams the farming woman and her helpers had started weeding from the boundaries of her farm towards the centre. They had given up, however, before finishing the job, probably because they lacked sufficient cocoyam cormels which they were planting as they went along. Therefore, in the centre of the farm, weeds continued to grow for another two weeks. Subsequently, most of the maize plants in the central part of the farm were significantly shorter than the ones in the parts that had been weeded earlier. The measurements presented in the charts p. 32 were taken by doing two cross-sections through the centre of the farm at right angles, and measuring all the maize plants along these lines.

The Effect of Weeding on Plant Growth (Maize Farm near Buea, compiled by the Author)


a) West - east cross section (width of plot)


b) South - north cross section (length of plot)

2.2.6 Manuring

Farms are usually not manured. As was mentioned above, soil fertility is restored by

- the fallow period,
- burning at the beginning of a new farming period.

The cultivated areas directly surrounding the houses are manured with all sorts of suitable materials, e.g.

- kitchen and household refuse,
- ashes,
- animal dung,
- waste from the processing of crops, e.g. coffee berry pulp.

Compost is hardly ever prepared. The often-quoted study on traditional African farming systems reports the following methods of manuring the compound farm:

- "mulching: all kinds of smaller branches, twigs and leaves from trees and shrubs are used for mulching the compound. The yam mounds especially are covered with a thick layer of these materials;

- animal waste: dung, mainly from goats, is applied throughout the year to the crops. It is usually applied to individual plants;

- ashes: as with animal waste, ashes are distributed directly around the individual plants;

- composting: this practice is common in Owerri-Ebeiri (a village with a high population density, H.B.) where grasses from the fallow areas are collected and thrown together with household remains, into pits where the materials decay. The resulting rich soil is then applied to the crops;

- shifting of latrines every year the latrines are shifted to another site within the compound. After a period of one cropping season the latrines are filled in, and bananas or plantains are planted, and so receive ample nutrients for many years. These manuring habits have not been developed to such a degree in the lower populated areas, . . . the labour-intensive way of building up soil fertility is a result of the people's efforts to overcome the increasing food shortage which results from the high population density." (Lagemann, J., 1977, p. 39)

Where ridges are built, a certain form of green manuring is sometimes used: At the beginning of a new planting season weeds, grasses and crop residues such as maize stalks are cut and gathered in the furrows. After this, neighbouring ridges are divided up and new ridges are built in the former furrows. Crops growing on the new ridges not only profit from the decaying plant material buried in the soil but also from nutrients that rain may have washed down from the former ridges.

2.2.7 Crop Husbandry

Nearly all farming done by smallholders uses the system of mixed cropping. Various crops are grown together on the same farm. Single cropping is only practised in the case of tree crops, most frequently with oil palms. There are good reasons for mixed cropping:

- The risk of crop failure is spread over various crops. If one fails, the other may still yield a harvest.
- Heavy infestation with a pest attacking a particular crop is less likely, as the distance between plants of the same kind is larger than with single cropping.
- Work on one and the same piece of land is spread out over time. Harvesting an early crop can be an extra weeding operation for the later crops.

- Intercropping tree farms with food crops is an inducement for women to help weeding the coffee or cocoa farm or even do it all alone. As they weed the food crops under and between the trees they mulch the trees at the same time.

- In some areas, land is so scarce that heavy food farming becomes a necessity on coffee farms.

As one author on tropical agriculture puts it: "By planting a succession of crops with varying planting times, rooting habits and maturities, the cultivator may make better use of his or her time, permit plants to tap the nutrients in various soil layers more effectively, distribute the risks due to vagaries of climate or incidence of pests and diseases, assure a more regular food supply and gradually, as the season progresses, cover the soil so well with vegetation that there is more effective protection against the effect of sun and rain and comparatively little need for the time-consuming job of weeding. Moreover, as long as only 'unimproved' varieties of crops are available or are used, the total yield from a given area may well be higher than when a single crop is planted in pure stand." (de Wilde, J.C., et al., 1967, p. 20)

The study from Eastern Nigeria provides further insights into the effects of mixed cropping. On compound plots, more than 40 species of useful plants were counted. These crops were planted very densely, coming close to bush or forest conditions which represent a stable system where soil fertility is continuously kept high. (Lagemann, J., 1977, p.35)

In the forest zones, trees and shrubs remain on the farms. "Most fields carry more trees and shrubs than commercial tree crop plantations." (Lagemann, J., 1977, p.43)

The reason suggested by the author for such a high plant density is that most of the plants are not vigorous because of the poor soil fertility. This seems to indicate that up to a certain extent the weakness of individual plants can be offset by an increasing number of plants. More important, he sees ". . . a deliberate effort by the farmers to maintain a dense vegetation in order to reduce leaching and erosion." (Lagemann, J., 1977, p. 43, emphasis mine). Continuous dense vegetation is also maintained by phased planting, i.e. planting at different time. A final conclusion is offered:

"The lower the fertility status the greater the number of stands and species grown on a given piece of land. Phased planting and mixed cropping are apparently tools to counteract the yield-depressing effect of a -decline in soil fertility." (Lagemann, J., 1977,p.46)

2.2.8 Crop Associations in Tree Crop Farms

The following is based on a farm survey carried out by the author in Cameroon. Conditions might be similar in many tropical countries.

Most newly established tree crop farms are used for annual crops as long as the trees are small, have not yet formed a canopy, and do not yet yield. As the tree plantations mature and shade most of the farm, all food crops except plantains and bananas tend to disappear. But even in old established tree farms cases of intercropping with annual food crops can still be found.

Coffee


Coffee

Out of 207 farm plots growing coffee, 63.7% are pure coffee farms, with plantains and bananas as food crops in most cases. 6.3% combine another tree crop with coffee, mostly cocoa and occasionally oil palms. All these farms have plantains/bananas and cocoyams. The annual foodcrop most commonly found in coffee farms is cocoyams/ colocasia (on 23.7% of all coffee farms), maize is much less common.

Cocoa


Cocoa

Of the surveyed cocoa farms, 42% are pure cocoa farms combining only bananas or plantains with the tree crop. The other farms all combine another tree crop with cocoa, most of the time oil palms which are dotted here and there on the farm plot and were probably left over when the farm was cleared. One third of the cocoa farms mix cocoa and coffee. Apart from plantains, food crops are rarely grown on cocoa farms, probably because the canopy, once formed, gives a heavier shade than on coffee farms. Intercropping with annual food crops is restricted to cocoyams/colocasia (25% of cocoa farms).

Oil palm


Oil palm

38.5% of the oil palm plots seen were pure palm farms. This low percentage is due to the fact that most of the time, oil palms are not planted but are exploited as they grow wild. People arrive at relatively pure oil palm plots by allowing wild palm seedlings to grow while cutting down other shoots. They may even transplant wild seedlings found elsewhere to their plot. These plots then contain trees of different ages; no attention has been paid to spacing, and usually, as the trees grow very high, there is enough light to allow the farming of food crops. Oil palm growing as practised by the plantations (CDC, PAMOL) is spreading slowly among smallholders. Palms are often dotted about on coffee farms (another 38.5% of the plots with oil palms). Food crops grown with oil palms are plantains/banana, cocoyams/colocasia, and cassava.

2.2.9 Crop Associations in Food Crop Farms

Food crops are rarely farmed as single crops, the only notable exception being cassava with its heavy demand on soil nutrients.

Cassava


Cassava

Apart from being planted as a single crop, cassava is farmed together with cocoyams, and sometimes with cocoyams and maize. Only very rarely is cassava combined with yams (on 17% of all cassava farms). Equally rare are plantains/bananas found on cassava farms.

Yams


Yams

Yams are equally often combined with maize and with cocoyams, but the joint farming of all three crops is very rare.

Colocasia

The association of colocasia with plantains/ bananas which is common on coffee and oil palm farms is also found on pure foodcrop farms. This association may be extended by yams, or maize and/or groundnuts. Occasionally, colocasia go together with other tuber or root crops, but they are intercropped with yams rather than with cassava.

Maize

Maize is never grown as a single crop. The association of maize with cocoyams or with plantains/bananas is very common, but all three crops rarely occur together. In the areas suitable for the growing of Irish potatoes, these are most of the time intercropped on maize farms. Leguminous crops like beans and groundnuts are much more common on maize farms than on farms without maize. Especially when cocoyams/colocasia and plantains/bananas are missing on a maize farm, the incidence of beans or groundnuts is very high. Egusi also are more commonly combined with maize than with cocoyam farming.

Irish potatoes

Irish potatoes are practically always mixed with another crop, mostly with maize and groundnuts/beans or with maize alone, and less often with cocoyams, yams, or cassava.

Other crops

African vegetables (huckleberries, "native carrots" etc.) are grown occasionally with other crops. They are slightly more often combined with maize than with colocasia but nearly never with cassava. Sweet potatoes do not seem to follow a regular pattern of mixed cropping.


Main Crop Associations

Note: Various other crops are usually grown on the plots where the above crop associations have been found. Here we show associations of major crops which, as association, cover the whole area of a given plot, omitting the occasional plant of hot pepper or okro dotted here and there. These associations are the most frequent ones, therefore, they seems to be those who are more viable.

2.2.10 Crop Sequences and Rotations

The crop rotations taught on the school farms are copied neither by the school leavers nor by the adult population nor even by the teachers on their private farms. Does this mean that one should abandon the teaching of crop rotation in school farm work as being ineffective? The findings presented below show that the local farmers, at least in some areas' practice definite crop sequences in a system of mixed cropping. In some cases, these sequences come close to real rotations because of the short periods of fallowing (one to two years) between the period of farming. It would seem as if the school farm rotations have been rejected because they insist on single cropping. We describe below the different crop sequences en. countered during our survey. It will have to be established through experimentation by the agricultural research stations and by the teachers in charge of school farms which of these are viable or can be made viable, and which ones will have to be discouraged.

Crop Sequences on Tree Crop Farms

As already mentioned, it is common practice to grow food crops on newly established coffee or cocoa farms. On coffee farms, mostly colocasia are farmed during the first three to four years until the coffee starts bearing. Occasionally, maize is added. More elaborate sequences of food crops with young coffee are:

Year

Crops

1

coffee, colocasia, maize, beans, groundnuts, vegetables

2

coffee, colocasia

3

coffee

Year

Crops

1

coffee, groundnuts

2

coffee, maize

3-5

coffee, maize

6

coffee

Newly established cocoa farms may be left for one or two years without food crops before cocoyams and/or maize are grown between the young trees. From the fourth or fifth year onwards, food crops are no longer grown systematically on cocoa farms. A more complicated sequence is this:

Year

Crops

1

cocoa, plantains, colocasia, cassava, maize, beans

2

cocoa, cassava, maize, beans

3-5

cocoa, cassava, maize, beans

6

cocoa

Intercropping on oil palm farms depends on the height of the palms and the shade they give. Bush clearing under oil palms ensures big bunches. But in order to benefit fully from the work of clearing, maize is grown under high palms.

In other regions, palm seedlings, which grow naturally on food crop farms, would be allowed to continue growing until they make food crop farming unprofitable. The following food crop sequence has been observed:

Year

Crops

1

oil palm, cocoyams, plantains, water yams, yams

2

oil palm, cassava

3

oil palm, cassava

4

oil palm

Crop Sequences in Food Crop Farming

Sequences starting with yams

There are short sequences covering two years of farming and one or two years of fallowing, in which yams are grown only during the first year.1.

Year

Crops

1

yams

2

cassava

3

fallow

Sequences with the usual mixed cropping are:

2.

Year

Crops

1

yams, plantains, colocasia

2

colocasia, maize, groundnuts

3-4

fallow

3.

Year

Crops

1

yams, plantains, maize, colocasia

2

plantains, maize cassava

3

plantains

4.

Year

Crops

1

yams, maize, beans, groundnuts

2

maize, beans

3-5

fallow

Then there are the sequence in Which yams are grown throughout, again mostly for only two years.

5.

Year

Crops

1

yams, plantains, maize, colocasia beans, groundnuts, sweet yams

2

yams, plantains, maize, colocasia, beans, groundnuts, sweet yams, cassava, sweet potatoes

3

fallow

6.

Year

Crops

1

yams, calabash, egusi

2

yams, calabash, egusi, maize, groundnuts

3

yams, calabash, maize, groundnuts

4-10

yams, maize, groundnuts

11-12

fallow

Similar sequences can be observed with sweet yams.

7.

Year

Crops

1

sweet yams, maize, groundnuts,

2-5

maize, groundnuts

6-7

fallow

8. Pattern 3 has also been observed with sweet yams instead of yams, but sweet yams cultivation went on for two years, and after that, cassava was farmed for four more years before a long fallow of about 6 to 10 years.

9.

Year

Crops

1

sweet yams, colocasia, plantains, vegetable

2

sweet yams, colocasia, plantains, vegetable, cassava

3

sweet yams, colocasia, plantains, vegetable, cassava, beans, groundnuts

Sequences starting with cocoyams but without maize

1.

Year

Crops

1-2

cocoyams

3

maize, groundnuts

4-10

fallow

2.

Year

Crops

1

cocoyams

2

maize, beans

3-4

fallow

3.

Year

Crops

1

cocoyams, plantains

2

plantains, maize, beans, groundnuts

3-5

fallow

4.

Year

Crops

1

cocoyams, plantains, colocasia

2

plantains, maize, groundnuts, yams

3-5

fallow

5.

Year

Crops

1

colocasia, egusi, vegetables

2-5

maize, beans

6-8

fallow

6.

Year

Crops

1

cocoyams, sweet potatoes

2-3

cocoyams

4-5

fallow

When the farming of a plot starts off with colocasia, most of the time this crop is only grown for one year and is replaced or interplanted by a cereal and one or several leguminous plants in the next year.

Sequences starting with colocasia and with maize

1.

Year

Crops

1

colocasia, maize, beans, egusi

2-3

colocasia, maize

4-20

fallow

2.

Year

Crops

1

colocasia, cassava, maize

2-3

colocasia, cassava

4-6

fallow

3.

Year

Crops

1

colocasia, maize

2

colocasia

3-4

fallow

5

yams, beans

6-7

fallow

4.

Year

Crops

1

cocoyams, maize, groundnuts

2

cocoyams, maize, groundnuts, beans

3

maize, groundnuts, beans

4-6

fallow

5.

Year

Crops

1

colocasia, maize, groundnuts, beans, vegetables, egusi

2-5

maize, groundnuts, beans vegetables, egusi, cassava

6-14

fallow

As can be seen above, when farming starts with colocasia and maize, most of the time colocasia are farmed throughout or at least through the major part of the farming period.

Sequences starting with maize but without tuber or root crops

1.

Year

Crops

1

maize, beans

2

yams

3

beans

4

cassava, cocoyams

5-7

fallow

2.

Year

Crops

1

maize,groundnuts

2-3

cassava

4

fallow

3.

Year

Crops

1

maize, plantains

2

plantains, cassava

3-9

fallow

Whereas these sequences incorporate a tuber or root crop later, mostly cassava, there are others with equally short farming period which leave out such crops altogether:

4.

Year

Crops

1

maize

2

okro, guineacorn

3-16

fallow

5.

Year

Crops

1

maize

2

beans

3

tephrosia as fallow crop

4

fallow

There are, finally, instances where maize is grown all through the farming period of the sequence:

6.

Year

Crops

1

maize, plantains

2

maize, plantains, cocoyams

3-5

fallow

7.

Year

Crops

1

maize, groundnuts, vegetables

2

maize, beans

3

maize, cocoyams

4

fallow

8.

Year

Crops

1

maize, groundnuts

2

maize, sweet yams

3-4

maize, groundnuts, sweet yams, beans

5-7

fallow

9.

Year

Crops

1

maize, egusi

2-10

maize, beans

11-16

fallow

Sequences starting with cassava

1.

Year

Crops

1-2

cassava

3

beans

4

maize, cocoyams

5-6

fallow

7

cassava

8

yams

2.

Year

Crops

1-2

cassava

3-4

cocoyams

5

maize

6-7

fallow

8

maize, groundnuts

3.

Year

Crops

1

cassava, maize

2-7

cassava

8-9

fallow

4.

Year

Crops

1-2

cassava, maize

3-5

cassava

6-10

fallow

Sequences starting with Irish potatoes

Irish potatoes are one of the few food crops introduced by the colonial powers. Being a tuber crop, it has been completely incorporated into traditional farming. Irish potatoes are grown in a variety of crop sequences. In one type of sequence, they are grown in the first year of a sequence of variable length.

1.

Year

Crops

1

Irish potatoes

2

maize, beans

3-4

fallow

2.

Year

Crops

1

Irish potatoes, maize, cocoyams, pumpkins

2

maize, cocoyams, beans

3

maize, beans

4-5

fallow

3.

Year

Crops

1

Irish potatoes, maize, beans, egusi

2

maize, cassava

3-5

maize, beans, cassava

6-7

fallow

In another type of sequence, Irish potatoes are grown through half or more of the sequence.

4.

Year

Crops

1

Irish potatoes, cabbage

2

Irish potatoes, cabbage

3

beans, maize

4

beans, maize

5-6

fallow

5.

Year

Crops

1-3

Irish potatoes, maize, cabbage, carrots

4-5

maize, cabbage, carrots

6-8

fallow

Year

Crops

1

Irish potatoes, maize, cocoyams, beans

2

maize, cocoyams, beans

3

Irish potatoes, maize, cocoyams, beans

4

maize, cocoyams, beans

5-6

fallow

There are sequences in which Irish potatoes are grown throughout, whereas other crops are added or dropped from the cropping pattern. The sequences covering more than four years of continuous farming always have maize associated throughout, and most of the time beans. The following short sequence brings in maize and beans only in the second year of the rotation:

7.

Year

Crops

1

Irish potatoes, colocasia, vegetables

2

Irish potatoes, colocasia, vegetables, maize, beans, cabbage

3+4

fallow

8.

Year

Crops

1

Irish potatoes, maize, beans

2

Irish potatoes, maize, cassava

3

Irish potatoes, maize, beans

4-5

Irish potatoes, maize, cassava

6-8

fallow

9.

Year

Crops

1

Irish potatoes, maize, beans

2

Irish potatoes, maize, beans, cassava, egusi

3

Irish potatoes, maize, beans, cassava

4-10

Irish potatoes, maize, beans

11-20

fallow

10.

Year

Crops

1

Irish potatoes, maize, colocasia, huckleberry

2-10

Irish potatoes, maize, beans

11-12

fallow

11.

Year

Crops

1

Irish potatoes, maize beans

2-5

Irish potatoes, maize beans, cocoyams

6-10

fallow

Sequences starting with upland rice

1.

Year

Crops

1

rice, cassava

2

cassava

3

cassava

4-16

fallow

2.

Year

Crops

1

yams

2

rice

3-12

fallow

3.

Year

Crops

1

rice

2

maize, groundnuts

3-4

fallow

5

groundnuts

6

fallow

Other sequences

1.

Year

Crops

1

sweet potatoes

2

groundnuts

3-9

sweet yams, water yams, colocasia, plantains

10-20

fallow

2.

Year

Crops

1

beans, groundnuts

2

groundnuts

3-10

cocoyams

11-13

fallow

3.

Year

Crops

1

groundnuts

2-3

colocasia

4-5

fallow

The cropping sequences and rotations shown above have been restricted to the main crops. Vegetables and minor crops have been left out. Here is a crop sequence, which shows all the crops grown on the farm plots:

Year

Crops

1

maize, colocasia, cassava, spotted beans, sweet potatoes, calabash egusi, pumpkin, melons, okro, garden eggs, huckleberry,

2

maize, colocasia, cassava, cowpeas,yams (very rare)

3

maize, groundouts

4

cowpeas

5

fallow

Source: H. Simon, W.A.D.A. Survey 1975, unpublished.

Notes: Information on crop association and sequences obtained as an average from five women. Only three out of the five women had farms in the 3rd and and 4th year. In the fourth year, groundnuts may be grown instead of cowpeas. If the land is infertile, fallowing starts already in the 4th year (adapted from WADA, a Programme of establishing a training centre for draught cattle, Wum 1975 p. 9a).

2.2.11 General Remarks on Crop Sequences

The information presented above is based on interviews with men on their farms. Since, most of the time,,they do little of the work on food crop farms, their information may not have been very reliable. Teachers are invited to examine critically the crop associations and sequences for mistakes. They will find it fairly easy to work out these associations and sequences in their own area. Pupils and their mothers will be very helpful in this respect. With these reservations in mind, what conclusions can be drawn from our observations?

1. Some crops are definitely more likely to start a crop sequence and be left out later usually after one or two years - than to be introduced into a farm plot which has already been used for some years. These crops are:

- yams,
- egusi,
- Irish potatoes,
- cocoyams,
- colocasia,
- rice.

2. Some crops clearly are more likely to be introduced later to a farm plot. These are:

- cassava,
- beans,
- guineacorn.

Cassava especially is usually introduced towards the end of a sequence when the soil has already been exhausted by the previous crops.

3. Maize and beans may start a crop sequence or may just as well be introduced later. in fact there are many cases where they are farmed throughout the time of farming one and the same piece of land.

4. Changes in the cropping pattern of a particular plot, i.e. dropping one crop and/or growing another crop, are most likely to occur in the second year of cultivation (dropping occurs in the second year in 70% of all cases, adding a new crop in the second year in 85% of all cases).
Usually, no additional crops are introduced after the third year of continuous farming. On the other hand crops may be left out, and thus the range of crops grown on a plot is reduced till the end of the sequence is reached and the farm plot is fallowed.

2.3 Instruments for School Surveys of Traditional Agriculture



2.3.1 Survey Schedules

Calendar of Farm Work (one crop only)

Enter the various farm work activities for the crop indicated in the heading in the order in which they occur. Indicate the time it takes to complete each task from beginning to end~by blocking in the respective rectangles in the body of the table. Thus if clearing for your crop starts at the beginning of February and ends in mid-march, you would block in the three corresponding rectangles.


Figure

This form gives a more detailed picture for one crop whereas the other form (below) makes possible a less detailed analysis of several crops at a time.


Figure

Survey Schedule on Farming in the Community
What crops are grown on the farms of the community? Please tick where appropriate!

Crop

For Consumption

For Home Consumption and for Sale

For Sale Only

(1) Crops containing mostly starch and sugar

a) Cereals:




maize

( )

( )

( )

guinea corn

( )

( )

( )

rice

( )

( )

( )

b) Root and tuber crops




yam

( )

( )

( )

cassava

( )

( )

( )

cocoyam

( )

( )

( )

colocasia

( )

( )

( )

sweet potatoes

( )

( )

( )

irish potatoes

( )

( )

( )

c) other crops




plantains

( )

( )

( )

bananas

( )

( )

( )

sugar cane

( )

( )

( )

fruit

( )

( )

( )

(2) Crops containing mainly protein

beans

( )

( )

( )

cow peas

( )

( )

( )

(3) Crops containing fat and protein

groundnuts

( )

( )

( )

egusi melon

( )

( )

( )

(4) Crops containing mostly fat

oil palm

( )

( )

( )

(5) Other Crops

vegetables

( )

( )

( )

spices

( )

( )

( )

kola trees

( )

( )

( )

coffe trees

( )

( )

( )

cocoa trees

( )

( )

( )

rubber trees

( )

( )

( )

tobacco

( )

( )

( )


2.3.2 Interview Guide for a Survey on Traditional Farming

In order to acquire a good understanding of traditional agriculture in your community, we would suggest that you collect information from individual farmers, both women and men. The best way to do this would be to discuss with them their various plots one by one. Such an investigation could be done with small groups of pupils. In that case, however, only a few of the topics treated in this guide should be taken up at one time.

1. Size of the Farm

See together with the woman or man in question as many of her/his plots as possible:

- number of plots farmed (by men in the household, by women in the household),
- size of plots.

It is difficult to know the approximate size of traditional farm plots since size in itself does not usually matter to the farmer. Plots rarely have straight boundaries, which makes exact measurement very time-consuming and difficult. We shall therefore propose methods of estimating the size of the plots approximately.
If the farmer knows the size of his farm plots, enter this information in the table below and specify the unit of measurement (hectare, acres, . . .)

If the farmer does not know the areas of his farm plots, proceed as follows:

(1) In the case of tree crop farms (coffee, cocoa, oil palms, raffia, etc.)

- If the farmer knows the number of trees, find out the average planting distance between the trees (by pacing the distance between a number of trees). Once you know the average distance you can estimate the total area of the plot using the formula:

Area = number of trees X (planting distance)2

- If the farmer does not know the number of trees, walk around the farm boundary, pace it out and draw a sketch on a piece of paper. Where the boundary is curved draw it in your sketch as a series of short straight lines joining up the main points. Find out the average planting distance between trees. Estimate the area of the plot from your sketch (for details see instructions at the end of this section). To get the number of trees, use the formula:

Number of trees = Total area of plot: (planting distance)2


Plots with tree crops


Plots with food crops (annual and biennial)

(2) In the case of food crop farms

Proceed as with tree crop farms where the number of trees is unknown and estimate the size of the farm plot from your sketch.

Many farmers have a large number of small plots scattered over a wide area. If this is so, you may not have the time to inspect all of them, although it would be desirable. Try to get an estimate of their size by asking the farmer and his wife/wives to compare them with the plots you have seen.

As far as farm size is concerned, you should now be able to find out the total area of the farm plots (by ad" ding all the estimates of size), the largest and the smallest plot, the average size of the plots (dividing the total area by the number of plots).

How to measure the slope of a farm plot

The slope of a farm plot is important because it has a major influence on erosion.
Especially in hilly areas it would be a good exercise to find out the slope, and also whether farmers control erosion, and if so, how. The following is a very simple method of finding out the gradient, which is a recognized measure of the slope.

- Cut a one-meter long pole and vertically place it in the ground at the bottom of the slope (A).

Ask someone to climb the slope until you see his feet on a level with the top of the pole (B). (Your own eye must also be on a level with the top of the pole.)

- Measure the distance between the base of the pole and your friend's feet (C). The gradient will be equal to A: C. Examples:

If C = 10 m, the gradient = 1/10 = 10% If C - 20 m, the gradient = 1/20 = 5% If C 2 33 m, the gradient = 1/33 = 3% The figure below shows 2 of the gradients. With a little practice you will soon be able to estimate the slope of a farm plot simply by looking at it.


Figure


Finding out the Gradient

2. Crops Grown

As you find out the size of each plot, make a note of the crops grown and enter them with the plot number and its area in the tables on p. 51. Complete for each plot by checking with the farmer, and ask him for information about the plots not inspected.

The tables now show for each plot the crop associations in multiple cropping for the current year. How far do these crop association agree with the ones shown in our documentation?

Indicate which crop will be harvested first and which ones later. Which crops are planted systematically all over the plot and which ones are dotted here and there? Use your own symbols to show this information in the tables above.

3. Farming Methods

a) When you prepare an unused plot for farming, how do you usually clear it?


forest

grassland

cutting down grass

( )

( )

cutting of shrubs and

( )

( )

bushes

( )

( )

felling trees

( )

( )

ringbarking trees

( )

( )

burning trees on the farm

( )

( )

leaving some trees for shade

( )

( )

covering grass with soil

( )

( )

leaving grass on the surface



without burning it

( )

( )

burning grass

( )

( )

using machinery

( )

( )

uprooting trees

( )

( )

other work involved in clearing



b) Prepare several tables of the type shown below and fill in one for a plot with food crops that has been burned, one for a food crop plot that has not been burned, and at least one for a newly established tree crop farm. (If there are not any, ask what was planted when the present tree crop farms were originally established.).

Type of plot: tree crops

( )

food crops only

( )

First clearing with burning

( )

without burning

( )


Figure

These tables will repeat at least some of the crop associations which have occured in previous tables. But they do more than that. They also show typical crop sequences according to the type of clearing used and the main crops grown (tree or food crops). The questions to ask are:

- What do you plant in the first year after clearing?
- What do you plant in the year after that? And what in the next year?

Continue the questions until the informant says that the soil would by then be exhausted, and the plot must be allowed to lie fallow.

Do the sequences and rotations match with any of those shown in the documentation? Which one is it? Do people in the community agree on the crop sequences or does every farmer have his own sequences? You can now also see how long food crops are grown in tree crop farms. How do people justify what they are doing in this respect?

c) For how many seasons can the farmer continue to farm a newly cleared piece of land until the soil is so exhausted that it must be allowed to lie fallow?

Number of years of continuous farming: . . . years

d) Some crops exhaust the soil faster than others. Can you tell, for the main crops in the respondent's farm, how long they can be grown continuously?

Crop

Number of Seasons of Continuous Farming







e) Once a plot is exhausted, how many years or seasons is it left fallow before it can be used again? Number of years left fallow: . . .

f) The table on p. 55 shows for each crop which methods could and should be used. Check for each of the crops farmed by the respondent which methods she/he uses and which ones she/he leaves out.

g) In order to compare results (e.g. total yield per hectare or yield per crop per hectare) in multiple cropping with yields from single cropping in ''scientific agriculture", you need to know how many plants there are per hectare. The number of plants per hectare is the plant density. It is not possible to count all the plants, on a given plot, and standard planting distances will not have been used from which the density could be easily calculated. Therefore, you can proceed by sampling. Your sample is a small area in which you count all the plants growing in it. From there you generalise to one hectare. The easiest way of taking a sample of this sort is to use a density square:

- Take a 20-meter long rope and 4 stakes. "Country-rope" will do.

- To find out where to make your survey, stand in the field and throw a stick behind you at random (your density square should be a random sample).

- Around the spot where the stick has fallen, draw a square of 5 X 5 meters (on a ground-nut field, 3 - 5 squares of 2 X 2 meters) by planting your sticks at the 4 corners and stretching the string around them.

- Count the number of stands or single plants of each variety within the square.

- Enter the figures in the table below and calculate the density per hectare using the formula: density per hectare = density per 25 square meters x 400

Note: You may add to your list rare species present on the field but not found within the square.
For a large (e.g. I hectare) farm, you will have to make several density squares.

Crop

No. of Plants in Density Square

Estimate for One Hectare













Total Plot



You will need one such table for each of the plots on which you use a density square.


Methods Used on the Farm

h) In order to see more clearly how multiple cropping is being done make a simplified graphical representation of the way crops are arranged on the farm. This means you will have to use two sets of symbols. First you will need one set of symbols to indicate the tillage.

You will need to invent another set of symbols to represent the crops. Examples are given p. 29/30. The following figures give three more examples.

In the first example, starting from the left pigeon peas are planted on the flat, then there is a ridge where early and late millet are planted. Next, there is a furrow planted with cowpeas, and on the next ridge, guinea corn and maize alternate. The following furrow has upland rice in it. The next ridge again has guinea corn and maize, followed by a cowpea furrow and another ridge of early and late millet. After that, two rows are planted on the flat, one row of pigeon peas and one row of pepper.

In the second example again starting from the left yams are grown on mounds, and they form rows. The rows of yam mounds have on each side of them rows of either groundnuts or bambara groundnuts planted on the flat. Between two rows of leguminous crops, there is one row of cereals, either late millet interplanted with early millet or maize alternating with guinea corn.


Intercropping Maize and Beans

(Graphic representation adapted from Bennet and Schork, 1978, p. 112)


Graphical Representation of Multiple Cropping Systems

4. Yields

In order to get information on this touchy question, ask the following:

For cash crops: How many bags of . . . can you harvest in a good year, and how many bags . . . in a bad year? Write down the range thus obtained.

For food crops: How many baskets of bags of . . . did you (your wife/wives) harvest last year, both for sale and for consumption? If you had to buy a basket/bag on the local market, how much would you pay? Enter the price per unit in the last column.

For plantains/bananas: How many bunches per week do you usually harvest? How many bunches do you eat in a week which come from your farm?

Of course it is difficult to get reliable information by asking questions. Except for cash crops, farmers simply may not be able to remember things in terms of numbers. Since you live in your school community, a more direct approach is possible. You can measure yields directly. Here are some guidelines on how it could be done for one crop at a time:

If the farm plot has been completely harvested:

- Count the number of baskets, bags or sheaves.
- Weigh one basket or bag or sheaf.

By multiplying the number of baskets by the unit weight (remembering to deduct the weight of the bags baskets, buckets, basins etc. used as containers) you can calculate the yield of the field. By dividing the yield by the area of the field (which has already been calculated) you will also obtain the yield per hectare for each variety.

If the plot is not fully harvested:

- You can estimate the average production of one plant (tuber, ground-nut) by weighing the tubers or the products of some twenty plants and dividing this weight by the number of plants whose production you have measured.

- Subsequently you can use the sample established in your density square to calculate the average production of one are (knowing that the 5 x 5 m2 density square = 0.25 are)


Figure

Example:

Average production of one yam plant = 2 kg. Density noted = 9 plants/0.25 are).

Density per are = 9 x 4 = 36 plants/are.
Production per are = 36 x 2 = 72 kg/are.

- You can then estimate the yields per hectare (in the above example: 7.2 T/Ha)

- Since you have already measured the area of the field, you will have no difficulty measuring the total production of the field (if the field is 20 ares, yam production may be calculated: 72 kg x 20 ares = 1.440 metric ton).

3.1 The meanings of scientific agriculture

School farm work so far has been guided by principles of scientific agriculture. Scientific agriculture in this context may best be described as the traditional European land-use system systematically changed and improved by applied science.

Any traditional land use system in the world tends to be well adapted to the conditions under which it works - works climate, the soil, the existing technology, the population density and social conditions. If changes in these factors occur slowly, the land-use system will be able to adapt to them, but adjustments are not usually fast enough to cope with rapid change. The slow pace of natural change in farming systems is due to the fact that a change of habit derives exclusively from everyday experience. Experience comes in the form of shortcomings and disasters on the one hand, and successful innovations on the other. Such innovations are often due to good luck and chance as much as to conscious efforts to remedy a deteriorating situation. Since these innovations, these new and better ways of farming, are always introduced by individual farmers, they will spread only very slowly, depending on how widely the farmers travel.

Scientific agriculture in Europe was the result of an approach that put the findings of scientific disciplines such as biology, chemistry, geology, and physics to the task of solving agricultural problems which European farming traditions alone, faced with an increasing population and urbanization, could not solve. This has resulted in a variety of land-use systems all permitting permanent cultivation. These systems all did away with the fallow year in the traditional three years' rotation. The major breakthrough in this respect was the application of chemistry to the problem of soil fertility. The exact properties of the plant nutrients were identified. Chemistry found ways and means of producing these nutrients so that the farmer did not have to rely exclusively on the slow natural processes by which they were made available in the soil. The resulting development of chemical fertilizers (also called inorganic fertilizers) has been very successful, and did more than anything else to establish the firm belief in the omnipotence of science in agriculture. Pesticides and insecticides, the systematic breeding of high-yielding varieties of all sorts of crops, farm machinery, sophisticated techniques of soil improvement and systems of crop rotation are all instances of the application of science to agriculture.

The next table contrasts scientific agriculture with both the approach followed in Rural Science as taught and practical in primary schools, and traditional agriculture. The table warrants careful reading since we shall comment only on some of its elements.

Factor

Scientific Agriculture

Rural Science Teaching

Traditional Agriculture

Soil




- preparation

- deep tillage

- shallow tillage

- shallow tillage


- removal of all shrubs and trees

- removal of all shrubs and trees

- tolerance of selected shrubs and trees

- leveling



- boundaries with straight lines and right angles

- boundaries with straight lines and right angles

- shape of plots not important

- improvement of soil quality

- drainage

terracing in some areas



- anti-erosion measures



- addition of limestone etc.



Crops

improving the quality of plant material through breeding for

careful selection of planting material

careful selection of planting material

- high yields



- adjustment to climate and soil conditions

introduction of new crops

introduction of new crops

- nutritive value



- resistance to diseases and pests



- taste, etc. introduction of new crops



Crop husbandry

- single cropping

- single cropping

- mixed cropping

- planting/sowing

- planting/sowing along straight lines

- phased planting
- planting at random on a given area lines

- exact planting distances

- exact planting distances

- no exact planting distances

- clean weeding (use of chemicals)

- clean weeding used as mulch

- some weed tolerance, weeds


- chemical plant protection (pesticides, insectides)

- no plant protection mixed cropping

- plant protection assured by

Source of power

traditional: man, draught animals modern: fuel-powered motors, electricity

man

man

Tools and Implements

traditional: specialized hand tools, animal- drawn implements modern: sophisticated engine-powered machinery

- African all purpose hand tools

- African all purpose hand tools



- specialized European tools for gardening

- a few European type hand tools

Because of the great successes achieved through science in European agriculture, methods developed for agriculture in temperate zones were transferred to the tropics with only minor adjustments. It took people some time to realize that scientific farming in the tropics meant more than identifying and breeding high-yielding varieties of crops. It meant that science would have to take an altogether new look at principles of soil preparation and crop husbandry, and that basic procedures and methods would also have to vary according to climatic and soil factors.

We shall comment briefly on the table:

Deep tillage using the plough needs farms without trees and shrubs as these would disturb ploughing. Advanced farming machinery such as the various sowing machines and harvesters need levelled land, i.e. farm areas where small depressions and holes are filled in and small elevations are levelled down so as to make a smooth surface. Farming along straight lines is also a requirement of cultivation techniques (weeding, application of fertilizer) that use animal-drawn or engine-powered equipment. This has so much shaped the appearance of the European and the American countryside that the newcomer in Africa had difficulty in distinguishing a food-crop farm from the bush, especially in the forest and tree savannah zones.

Manuring differs for gardens and farms. Traditionally, farms were fertilized with farmyard manure. But farmyard manure is available only where animals are kept in stables so that their dung, mixed with the straw used for bedding, decomposes to form a very rich mixture that is ploughed into the soil. In Africa, where farming and livestock rearing are usually done by quite different groups of people, farms do not produce any farmyard manure. Compost is prepared and used in vegetable gardens that are much smaller in size than fields. Preparing good compost is so much work that it cannot be applied to farms far away from the compound, although it might prove feasible for nearby farms. As mentioned above, compound farms are manured by all sorts of household refuse and animal droppings thrown on the top of the soil as a kind of a mulch. Composting all these items and hoeing them into the soil at the time of farm preparation and/or planting would provide more soil nutrients.

The science-based methods of improving soil quality have permitted the cultivation of land formerly thought unsuitable for farming. By careful drainage, waterlogged areas have been put to use. By adding limestone and other substances, the structure of the soil has been changed to suit various crops.

"The Green Revolution" is a slogan denoting spectacular developments in agriculture due to the breeding of high-yielding varieties of rice, maize, and wheat. With cereals such as these, the most surprising yields were achieved by careful crossbreeding of a large number of varieties of the same cereal. Similar attempts have now been made in the case of root and tuber crops, and specialists assert with confidence that they can breed almost any desirable quality into a given plant. However, as far as high yielding varieties are concerned, there is a drawback: they thrive only under optimal conditions and thus are very demanding on the farmer. The right planting time, correct spacing, the right amount of water, no competition from weeds, chemical fertilizer and chemical control of pests - all are required in order to assure the heavy harvest these varieties are able to yield. Some of these requirements involve a lot of work, some mean heavy financial expenditure. It is not surprising, therefore, that the result of this kind of Green Revolution has been that the rich landowners have profited most while smallholders have not been able to buy the necessary artificial fertilizers and pesticides even when seed material was distributed free.

Exact planting distances are justified by considerations about the growth of roots and competition between plants. The best planting distance obviously is such that the root systems of neighbouring plants just touch each other when fully grown. If they are further apart, parts of the soil are not used. If they are closer together, they compete for soil nutrients and will not grow to be healthy plants. This is certainly true for single cropping where all the plants on a plot apart from the weeds - need the same kind of soil nutrients. One would have to reason differently when it came to mixed cropping.

In case of single crops, pests and diseases particular to the crop being farmed find ideal conditions. Many high yielding varieties are more vulnerable to pests and diseases than varieties with lower yields. Plant protection by means of chemicals therefore becomes important. Since in mixed cropping plants of the same species are further apart than in single cropping, pests and diseases do not spread as fast as in single cropping, and, some plants, even some weeds, seem to keep away pests from other species. The best known example is the pyrethrum flower which East African farmers grow as a cash crop, and which forms the basic ingredient of most insecticides. Vegetable gardeners in Europe know, for instance, that it is advantageous to plant carrots and onions in alternate rows. The onions drive away certain insect pests which attack carrots, and the carrots keep out a pest which feeds on onions.

Finally it must be pointed out that today's modern scientific farming is highly mechanized and labour saving. It would not be possible, otherwise, for five percent of the population of the industrialized countries to feed the rest and produce surpluses for export. But this type of agriculture is certainly not suitable for areas where unemployment is a big problem and where all the farm machinery would have to be imported from abroad, using up scarce foreign exchange.

3.2 Scientific agriculture in Cameroon



3.2.1 Peasant Farmers

The first table shows an example of how smallholder farmers in Cameroon use modern methodes in coffee and cocoa farming. The second table shows what planting distances have been recorded on cocoa and coffee farms. Acceptable planting distances are framed.

Planting distances depend among other things on the fertility of the soil. Therefore, we have defined a range of planting distances as being correct rather than just one. For coffee, this range lies between 1.5 m and 2.5 m. For cocoa it is higher and lies between 2.5 m and 4.0 m. A relatively high proportion of coffee and cocoa farms in the forest zones show very high planting distances, sometimes double the required distance. This is due to the fact that on some farms cocoa and coffee trees are mixed which requires larger distances between the trees of one species. From advanced statistical analysis one can conclude that modern methods of tree crop cultivation have a comparatively small effect on the income derived from the tree crops. Taking the example of coffee, the most important factors accounting for high income are

- the total number of trees owned,
- the employment of skilled labour (e.g. for pruning and spraying),

- the use of modern methods like skilled pruning, weeding, and mulching, the use of fertilizer and chemicals for spraying.

- the use of selected planting materials, especially important in the South-West Province.

Thus, for the average farmer with his limited resources and financial possibilities it was, at the time of the research, more profitable to extend his coffee or cocoa farms in size than to increase his own efforts or to employ hired labour in order to apply the recommended farming methods, or to buy costly materials like fertilizer and insecticides or pesticides.

Method

Per Cent of Sample Farmers

Remarks

Single cropping in food crop farms

4.2


Preparation and use of compost manure

4.7

Very demanding in terms of labour

Crop rotation or sequence

9.8


Use of selected planting material for coffee, cocoa or oil palms

15.9

Most farmers raise seedlings themselves from coffee berries or cocoa beans. Some farmers establish nurseries and sell seedlings. The department of agri- culture is setting up nurseries for the distribution of selected plants.

Fencing the farm

16.4

Farms not fenced suffer damage from animals - mainly goats in the forest zones and goats and cattle in the grassland savannah.

Use of chemical fertilizer

20.6

Fertilizer is only applied to tree crops. Farmers lack confidence in the beneficial effects of fertilizers and are poorly informed about the way it acts. Also, there are frequent shortages of supply.

Shade trees in young coffee and cocoa farms

28.5


Single cropping in tree crop farms

32.2

Even if allowance is made for the growing of food crops in young tree farms, intercropping is done to a large extent on mature tree farms.

Insecticides and pesticides

32.7

Spraying against pests and diseases on coffee or cocoa farms is recognized as important, but the necessary chemicals were in short supply at the time of the research.

Correct spacing of trees (planting distances)

44.9

For details see table on planting distances.

Mulching

46.3

Mulching is mostly done in young tree crop farms and in yam farms.

Pruning

75.7



Planting

Coffee Farms

Planting

Cocoa Farms

Distance (m)

Forest

Savannah

Distance (m)


below 1.5

5.7

5.5

1.0 -1.5

5.9

1.5-1.99

20.8

13.7

1.51-2.0

2.9

2.0-2.29

17.0

30.1

2.01-2.5

11.8

2.3-2.49

3.8

6.8

2.51-3.0

17.6

2.5-2.89

9.4

15.1

3.91-3.5

17.6

2.9-3.49

15.1

13.7

3.51-4.0

8.8

3.5-4.49

15.1

8.2

4.01-4.5

8.8

4.5 and above

13.2

6.8

4.51-5.0

8.8




5.0 and above

17.6

Total

100.0%

100.0%


100.0%

number of farmers

53

73


34

percentage of farmers with




acceptable planting distances

41.5

50.7



We have already seen the large differences in the use of modern, scientific farming methods, even in tree crop cultivation where these methods-are better adapted to tropical conditions than in food crop farming. What could be the reasons for these pronounced differences? One important factor is certainly the available of training and good examples. Thus, coffee farming in the communities around the Santa Coffee estate was much better than, for example, in other area . Surprisingly well kept farms were also found in a subdivision, from where people migrate to the coffee estates between Foumban and Bafoussam, and in the northern Bakossi area where people migrate to the coffee farms around Nkongsamba for seasonal work.

In many cases, plantation workers came back to their place of origin, took over the farms of their parents, and tried to apply what they had learnt during plantation work.

3.2.2 Teachers, Schools, and School Leavers

The methods advocated by Rural Science are a blend of African and European farming methods, applied largely to African crops but also to vegetables and other garden crops brought in from Europa. All the expensive methods of scientific agriculture have been left out as schools would not be able to pay for them. "Rural Science" emphasizes crop husbandry where much more effort is required than by traditional crop husbandry procedures. The contrast between Rural Science and traditional farming is striking although many of the new methods of scientific agriculture, like soil improvement, plant breeding, and equipment in the form of sophisticated tools and machinery have been left out. The actual situation can be summarized as follows:

"The results are not very encouraging. Many parents are not convinced that the agricultural techniques of the school are superior to their own. Student graduates (i.e. school leavers, H.B.) seldom apply their acquired knowledge." (Bergmann, H., 1978, p. 9).

"How alien the content of the instruction has remained is evident in the fact that many teachers themselves do not even see to it that their own field are tended in accordance with the methods prescribed by the curriculum." (Bergmann, H., 1978, p. 10)

A hand-out distributed by IPAR-Buea states this as follows:

"Most teachers are not convinced as to the usefulness of 'scientific agriculture'. They therefore either apply local farming methods wholesale or practise a mixture of the two sets of methods. Educationally, this is disastrous, because children know what is happening very well (often, some of them are sent to work on teachers' farms during periods of manual labour). Teachers should therefore feel free to seriously reconsider local ways of farming and should have the courage to apply what seems useful to them on the school farm." (Bergmann, 1977, p. 3)

The conclusion therefore is:

"The basic mistake of existing curricula is that they apply European principles to the agricultural field. This makes translation of the subject matter into practical application for daily living difficult, and this applies to teachers as well as to parents and students." (Bergmann, H., 1978, p. 10)

If what is taught in school is not applied in practice, this means that the teaching has failed.

If, despite such failures, teaching is not changed to incorporate methods that can be used, this shows a frightening lack of realism.

3.3 Conclusion

It is not only the school which experiences this failure. In a study on farming in Northern Ghana, Bennet and Schork state:

"The question should be posed, however, why then, after so many years of discouragement by extension agents and technical advisors, do so many farmers in Northern Ghana, as well as other parts of West Africa, continue to practice these methods (the traditional ones, H.B.). A critical examination may yet prove these techniques to be of the highest value as a basis for the upgrading of -the indigenous farming predicament." (Bennet and Schork, 1979, p. 103/104)

The Rural Education Centre at Umuahia, Nigeria, has attempted continuous cultivation based on a heavy dressing of compost manure. As the figures on crop yields over a period of 20 years show, yields seem to be stable at or even above the initial level. Maize yields rose from one ton per hectare to roughly 2.4 tons per hectare, yam yields fell from eight to below seven tons per hectare but rose afterwards to nearly nine tons per hectare. Cassava yields did fluctuate strongly but seem to be generally on the rise. Yet this experience seems unique, and is limited to areas small enough to be manured by compost.

Another experiment conducted at the Agricultural Research Station at Umudike leads to rather pessimistic conclusions. Here are the main facts:

"The problem of declining soil fertility resulting from washing and leaching of the principal soil nutrients led to the question of whether continuous cultivation could be introduced. Researchers conducted experiments with green manuring in order to replace fallowing. For this reason a six-year trial rotation incorporating different cover crops was set up in 1924 at the Agricultural Research Station at Umudike . . . During the first years the reports were optimistic . . . After . . . completion of the experiment a total failure had to be reported: 'As a result of seven years experimental work with continuous cultivation, incorporating green manure, it has now been established that the system as practised at Umuahia is not compatible with the maintenance of soil fertility . . . whereas the fertility of the 'native' plots was just as high as it had been in 1925, that of the continuously farmed plots had fallen practically to nil'." (Lagemann, J., 1977, p. 14/15).

14 native plots were checked for comparison. They yielded an average of 12.2 tons of yams per hectare. The plots-under continuous cultivation yielded, after seven years of farming, 4.7 tons per hectare. Lagemann concludes:

"The search for a feasible technology which is able to hold or even improve soil fertility under continuous cultivation has not found an adequate answer and this is still one of the main problems for research in the humid tropics." (Lagemann, J., 1977, p. 17)

But scientific agriculture as conceived by those who drew up the syllabuses for Rural Science has not only disappointed its supporters in the tropics. Fertilizer and chemicals against pests and diseases are used in such large quantities and often so carelessly that health hazards and widespread pollution of the environment have become a real danger. Alternative farming methods are being tried out by a number of people. A fresh look at traditional African agriculture would therefore be in keeping with this worldwide movement.


Average Yields of Crops - Rural Education Centre Umuahia 1940-1960

(Source: Obi, J.A., and Tuley, P., as reproduced in Lagemann, J., Fig. 1, p. 17)

4.1 The need for a new approach

The approach to the development of agriculture favoured by the colonial powers in Africa must be considered a failure. The following statement bears out the concluding remarks of the previous section.

"In spite of extension efforts, mixed cropping has given way to pure cultures* in only a few regions in Africa, and it is relevant to consider whether technological progress could be achieved more widely through the improvement of mixed cropping than by persisting in attempts to replace this practice by pure cultures." (Tourte, R., and Moomaw, J.C., 1977, p. 304)

Accepting the old approach to agriculture development as wrong is one thing, recognizing the traditional farming systems as reasonable and well-founded is something different:

"We consider it wrong to characterize the farmer as dumb and backward and to consider his working methods as something which must be completely replaced by modern methods." (Eager, K., and Mayer, B.J., 1979, p. 8)

The two statements do not mean, however, that one can safely sit back and rely on individual farmers making the adjustments necessary to cope with changing conditions. There is widespread agreement that the old, stable system of shifting cultivation has given way to a system of bush fallowing with ever shorter fallow periods. This is due mainly to population pressure and it cannot restore the fertility of the soil. The old system with very long fallow periods has been replaced by-" 'mining' systems of farming which generate a more or less rapid decline of the soil fertility . . . land becomes a limiting factor . . . while natural fertility diminishes . . . the capital resource of the land is likely to be degraded by extensive cultivation." (Tourte, R., and Moomaw, J.C., 1977, p. 298)

The International Institute of Tropical Agriculture (IITA) at Ibadan plainly states:

"The fact is that the countries in the humid tropics are finding it harder and harder to grow enough food for their people." (International Research in Agriculture, 1974, p. 34)

At the same time, with really suitable farming methods, food shortages need not become a problem for a long time to some.

"The food-producing potential of these lands is unknown - some estimate it to be very great." International Research in Agriculture, 1974, p. 34)

". . . the abundance of rain in conjunction with high temperatures endows this zone . . . with high production potential: nearly 4 times that of the temperate zones." (Tourte, R., and Moomaw, J.C., 1977, p. 296)

This means that one hectare of land in the humid tropics could produce four times as much as one hectare of land in a temperate climate. If this is true, then most African countries could feed, from their own resources, a vastly higher population than the one they have at present. Yet, an equatorial country like Rwanda is likely to face problems of acute food shortage, of famine, in the immediate future. One of the main reasons is that tropical soils are very vulnerable. The same factors that sustain dense vegetation can constitute a major danger:

"Under continuous cropping, the abundant sunshine and rainfall soon become a liability, tending to aggravate soil erosion, leaching, and nutrient depletion." (International Research in Agriculture, 1974, p. 35)

But erosion and leaching are already a danger now that the fallow periods are being shortened. The conclusion from all the arguments presented above is simple:

"If the practice of shifting cultivation is to be superseded - and pressures on land and food supply rule that it must be - new means have to be found to conserve moisture, restore organic matter and preserve soil fertility, prevent erosion and leaching, control weeds, keep down insect and nematode populations (all of which the bush fallow achieves), and in addition support continuous cropping and produce higher per-unit yields." (International Research in Agriculture, 1974, p. 35)

This situation holds both great dangers and high hopes. The old approach to agricultural development has not brought the solution. Therefore it becomes the more important to look for better solutions, new approaches. We shall discuss a limited range of such approaches because

- they justify a departure from the view of farming embodied in the old Rural Science,
- they offer new lines of teaching and learning,

- they contain suggestions that could be tried out in school farm work and in observational activities,

- they link up with traditional farming techniques, encouraging teachers to do away with the break between what is taught in school and what is put into practice by parents, pupils, and teachers out of school.

- they indicate areas of fruitful cooperation between school and research geared to national development.

These approaches are

- the zero tillage or minimum tillage approach, "biological" farming,
- the development of farming systems for the lowland tropics (IITA),
- eco-farming.

All these approaches are very similar to each other. They all agree that modern agriculture as practised in the industrialized countries should be rejected. They differ with regard to the emphasis placed on various cultivation methods.

4.2 The Main Approaches



4.2.1 The Zero Tillage Approach

Zero tillage is an attempt to cope with soil erosion. Where it can be applied, it also reduces the amount of labour needed. For a description of the approach and the reasoning behind it we shall turn to an article by an American, John Holway:

"For centuries American farmers have been turning the earth every spring of fall and laboriously cultivating weeds all summer. Now they're discovering that, without their prows, they can grow as much - and sometimes more - while also saving money, time, labor, energy, water, and - perhaps most important of all - saving soil . . .

No-tillage - it's also called 'zero tillage', 'minimum tillage', 'conservation tillage', etc. - rests on two revolutionary principles:

One, the plow may be the soil's worst enemy, breaking it up and leaving it at the mercy of wind and water erosion.

Two, mulch from last year's crop may be a valuable tonic for both soil and seedling. It holds moisture around the plant and helps choke off weeds. . .

The plow was good for Europeans with their soft rains. It increased their food supply so they could colonize the rest of the world. But they also carried the plow with them, and now the whole world is battered by this European system which isn't suited to any area of the world except Europe. . .

William S. Greiner, lowa's director of soil conservation, estimates that the state loses an average of 10 tons of soil per acre (25 tons per hectare) every year. On sloping land that could reach 25 tons per acre (62 tons per hectare). We are losing about an inch of topsoil every 12 years', Greiner says. 'A century ago Iowa had an estimated 14 inches of topsoil over most of the state. Today half of it is gone. If no conservation is practiced, the rest will be lost in another 36 years', he predicts." (Holway, J., 1978, p. 16)

"Nearly 25 percent of our cropland is being damaged at a rapid rate of erosion. This is an area of something over 100 million acres of cropland. The productive capacity of much of this highly vulnerable land will be permanently damaged and around 500.000 acres a year ruined for further cultivation unless and until it has the benefit of sound conservation farming within the next 10 to 15 years. On another large area (around 115 to 120 million acres) of cropland, erosion is taking place somewhat less rapidly but still at a serious rate." (Smith, R., 1977, p. 7)

Soil erosion can be checked, however:

"The way to do it is to plant on terraces following the contour of the land, without plowing, and leaving last year's stalks and other residue on the ground as mulch.

About 40 years ago some U.S. farmers began leaving a stubble mulch on their fields after harvest. It was the first step toward a minimum-till system. It was not until the 1950s that farmers discovered that they could prepare their seedbeds and plant all in one operation, eliminating at least one trip over the field. But without plowing, weeds multiplied and yields went down. Then, with the introduction of the new herbicides such as 24-D, farmers could give up plowing too, letting the chemicals do the work that prows had formerly done.

Ingenious new machines were developed to open a narrow slot in the soil, deposit the seed, cover it lightly, fertilize it, and deposit herbicides and pesticides, all in one operation. The biggest machines could do up to 16 rows at one time. The mulch left between the rows catches and holds the rain water, while helping to suppress weeds. The need for additional trips over the field is reduced. The fewer trips over the soil, the less it is compacted. . .

No-till has also extended croplands into thousands of acres of hillsides too steep to prow, into other soil impossible to plant, and even into sandy soil formerly fit only for pasture. In fact, no-till works best on hills - it needs plenty of drainage. It's not so good on poorly drained land or on clay soils - the mulch holds too much water there.

. . . about one-third of the energy consumed on U.S. farms is in tractor fuel. By eliminating unnecessary trips over the field, this bill can be cut in half. Average savings nationwide: an estimated 850 million gallons a year.

One-fourth of a farm's energy expenditure is in the manufacture of nitrogen fertilizer. Because no-till cuts down on water run-off, less of this expensive fertilizer is washed into the rivers as pollution. Insects and plant diseases are a problem - but no more so than in conventional tillage. In fact, the mulch cover in no-till fields protects the earth worms that keep the soil aerated. And no-till farmers report yields at least as high as under conventional tillage. Often they are higher:

The U.S. 1975 record crop yield was set on an Illinois farm that hadn't been plowed in six years. When double-cropping is added, the yield per acre is even higher.

No-till saves the soil

Erosion protection is even more dramatic. In one Ohio test plot, a single five-inch rainfall washed 20 tons of soil off a conventionally plowed field with a seven percent slope. A neighboring no-till field with a 20 percent slope lost only 100 pounds . . .

Wind erosion can be even more damaging than rain. In the 1930s in the U.S. Southwest, clouds of dust obscured the sun and drifts of earth covered the highways. In a recent test in Ohio, in a severe windstorm a plowed field lost 130 tons of soil. The loss on a no-till farm in the same storm: two tons.

Yet only one out of seven erodable acres in the United States is planted in minimum-till. Only one in 40 is planted in no-till. Why? For generations farmers have been taught to be proud of their "clean" fields of black, weed-free soil between the rows. Stubble or mulch on the field looks like "trash" in some farmer's eyes. But as they see their neighbor's no-till fields producing as much or more with less work and money, they make the change themselves.

Solution for the Third World?

Can no-till succeed overseas? Even Europe, which invented the plow in the first place, is beginning to use it. Many authorities warn that it cannot be used successfully in the developing countries. Herbicides are essential to the system, they say, and their cost is prohibitive. The no-till planting machines are another prohibitive capital cost. And a very sophisticated level of management is required, these experts say. Nonsense, say others. The system is working now in Brazil, Argentina, Colombia, Uruguay and Rhodesia, Professor Young of Kentucky maintains. The high temperatures of tropical soils can damage seedlings. A mulch helps keep the temperatures down. For farmers who can afford to, small two-row planting machines are available for under $ 1000. They can even be drawn by an ox. For others, a hoe can do the same job. Much subtropical agriculture is now very near no-till farming. A farmer can easily substitute labor for herbicides, hoeing weeds by hand as farmers have for centuries. . .

Buchele worked with farmers in Ghana in 1969. They harvested grass for the extra mulch they needed, raked the straw off the seedbed by hand, planted, and raked the straw back over. They planted on ridges eight inches (20 centimeters) high. 'Our tests show', he says, 'that you should leave one ton of crop residue per acre.'

Kimberlin has had similar experiences working with farmers in Paraguay. They set up new colonies using very simple tools, no chemicals and an ample supply of family labour. They chopped off the weeds to form a mulch, planted their crops in rows of 90 degrees to the slope, and let the mulch catch the rains. A man just about has to use no-till where only the simplest tools are available. In some climates, for instance in parts of Europe, and in some soils the plow is still needed. But around the world more and more farmers are learning how to turn a profit without turning the soil". (Holway, J., 1978, p. 17).

The IITA at Ibadan is experimenting with this approach, and the institute's appraisal of the method is encouraging:

"Mulching and minimum tillage, in combination with weed control measures, have been found to have several advantages, including keeping top soil in place, holding moisture reserves in the upper layer of cropped soils, and lowering soil temperature. Marked benefits were recorded in both yam and maize crops.

Leaving crop residues on the ground after harvest . . . and sowing the new crop through the layer of felled weeds, are variations of the same approach. Like mulching and zero tillage, they mimic the bush fallow system, and are . . . a good deal handier. This tactic has given good results with maize. " (International Research in Agriculture, 1974,p.37)

4.2.2 Biological Farming

"Biological" Farming is a farming system which tries to do without inorganic inputs as much as possible. The soil is fertilized with farmyard manure and compost instead of chemical fertilizer. Weeding replaces the use of herbicides that are highly poisonous. The crops are protected against insect pests and diseases by careful crop rotation, by a certain amount of mixed cropping, and by interplanting certain plants that are known to keep insects away. Biological farming in this sense must be seen, in the industrialized countries, as a conscious rejection of certain forms of industrial and scientific progress. It is a reaction against environmental pollution: some of the chemicals in common use do not decompose fast enough and start poisoning people and animals. Insecticides do not only kill insect pests but also a large number of harmless or even useful insects like bees. At the same time, they favour the development of pests that are immune to insecticides so that higher and higher quantities of insecticide and more and more poisonous substances have to be applied. Often, too great a quantity of chemicals is used. Some of them get washed into the soil, disturbing soil life. A lot of the fertilizer applied to the land is not used up by the crops. It leaches away into the underground water and seriously affects life in rivers and lakes. As people became aware of these large-scale harmful effects of agricultural "progress", the idea of "biological" farming was evolved in order to counteract them. What it does do in the African context is to serve as a warning against uncritical acceptance of just any kind of "progress" and "modern methods".

4.2.3 Farming Systems for the Lowland Tropics

Let us take the case of the IITA at Ibadan to illustrate various attempts to arrive at viable farming systems. We have seen above how pessimistically the institute views the future of agriculture if things remain the way they are. One major task of the institute is to develop farming systems which are stable, i.e. which maintain soil fertility. At the same time, they have to rely on existing technology - the mechanization available in the industrialized countries is no solution for a variety of reasons. Also, the farming systems must be adapted to the farmers' present level of knowledge and skills. Farmers will not agree to change their work habits thoroughly unless the benefits from such change are substantial. The new farming systems furthermore must not require too many farm inputs like fertilizer and pesticides since a steady supply of them cannot always be guaranteed and their cost keeps rising. Therefore the proposals for new farming systems include such features as minimum tillage: apart from its beneficial effect on sloping land it reduces the amount of labour required, compared with traditional methods:

- multiple cropping: crop combinations are recommended that cover the soil throughout the rainy season, thus reducing erosion; they ought to incorporate crops that fix nitrogen, and crops producing a large amount of residue. Residues like stalks and leaves are needed for mulching;

- mulching: this has the advantage of further reducing erosion and leaching. At the same time, the mulch provides soil nutrients as it decomposes;

- tree crops: they are to be included for their climatic effects - they provide shade and humidity - their usefulness in checking erosion, but also for their function as nutrient pumps (see below for further explanation)

- chemical fertilizer and insecticides: "High rates of fertilizer are needed to produce the required mulching material. Insecticides are needed to decrease the risk due to insects, and are usually required to maintain luxurious growth of crops. Chemical Inputs can therefore be a substitute for the use of expensive machinery. The application of inputs is possible even on very small field . . ." (Lagemann, J., 1977, p. 133)

One such proposal for a complete farming system for the lowland tropics is presented in the study of traditional farming system in Eastern Nigeria. Taking account of differences in soil characteristics, it contains the following elements:

- valley bottom development,
- modern tree crop plantations,

- improvement of farming methods for annual and biennial foodcrops in farms at a distance from the compound;

- multi-storey cropping on compound farms.

The study maintains that in Eastern Nigeria, valley bottoms with their fertile, humid, but often poorly drained soils, are hardly used. A similar situation certainly exists in Cameroon in the regions bordering Nigeria. Swamp rice is suggested as a rainy season crop, locally consumed vegetables as dry season crops. Swamp rice means learning to farm a new crop altogether (see section on rice) but it fetches a high price, and since rice is in high demand in Cameroon, growers are assured of a large domestic market independent from changes to prices on the world market. Where valley bottoms are already used for the cultivation of raffia palms, this proposal might have limited application.

Vegetable growing is highly profitable when urban markets can be supplied. Since the land need not lie fallow in swamp rice cultivation, two crops per year could be harvested from the same area on a continuous basis. As tree crops, the study suggests high-yielding oil palms. Tree crop plantations should be established especially on land threatened by erosion ". . . because erosion and leaching are much more easily reduced by tree crops than by annual or biannual crops." (Lagemann, J., 1977, p. 121)

High yields are possible only if palms are not intercropped with food crops, but on the area between the palms a cover crop could grow producing mulching material for the food crop farms. Improved oil palm varieties should replace the local ones, the study suggests. Yields per hectare could thus increase five to seven times, compared with yields from wild palms, and the fat content of the improved varieties is higher. Introducing hand-operated oil presses to replace the traditional method of oil extraction would further increase oil production and income.

The improvement of food crop farming would have to happen within the traditional farming system instead of replacing it by something entirely different. Multiple cropping, minimum tillage and mulching are regular features here. Research at IITA has shown that multiple cropping produce higher yields per hectare than single cropping; this is shown in the table p. 74.

For IITA it is obvious that mixed cropping needs a certain minimum of chemical fertilizer if soil fertility is to be maintained under -conditions of continuous cultivation. But it is known from scientific research that certain types of chemical fertilizers are much more effective used in conjunction with mixed cropping with its high plant density than they are with single cropping. It follows, therefore, that yields from mixed croping would rise faster than the amounts of fertilizer needed.

Trial

Crops

Month of Planting Cassava

Total Yield (tons/hectare) (dry matter)

No.

Maize

Melon

Cassava



1

x




4.49

2


x



1.02

3



x

April

14.95

4

x

x



4.66

5

x


x

April

15.17

6

x

x

x

April

16.15

7



x

May

15.79

8

x


x

May

15.63

9

x

x

x

May

15.96

10



x

June

11.84

11

x


x

June

15.59

12

x

x

x

June

23.73

13



x

July

10.47

14

x


x

July

14.15

15

x

x

x

July

12.99

16



x

August

7.46

17

x


x

August

11.73

18

x

x

x

August

10.30

Note : Maize and melons are planted in April. Cassava was relay intercropped (i.e. planted later than maize and melons) in the most of trials. Yield refers to dry matter. This means that after harvest the whole crop including leaves and stalks were dried and weighed (adapted from Lagemann, J., 1977, p. 129, table 47)

Since mulching is a necessity in the improved farming system, farmers must make sure that enough mulching material is available. Two alternatives are proposed:

"- arable crop and mulch production on separate plots but close to each other. Mulch production has to be very high on a relatively small plot . . . A production of 30 t mulch/ha requires 25% of the total land available for arable crops for mulch production if 10 t mulch/ha are to be reapplied to the crops.
- trees with a cover crop alternated with narrow but long strips of arable crops, e.g. improved oil palm grown in monoculture with a mulch cover, which serves two purposes: firstly high outputs from oil palms can be expected, and secondly large quantities of mulch will be produced which is applied to nearby fields . . ." (Lagemann, J., 1 977, p. 134)

Finally, the multi-storey cropping system has emerged from careful analysis of the farm compound. The name is due to the fact that on a well-cultivated compound - much like in the forest - there are several layers or canopies of leaves at different heights. These layers are then likened to the various ceilings in a house with several storeys, hence the term "multi-storey cropping".

"The crops (in a multi-storey compound farm, H.B.) can be divided on a height basis into 9 different groups:

Tree crops

- oil palms, coconuts (20-25 m high);
- breadfruit, raffia palms, oil beans, avocado pears (12-20 m high);
- cola-nuts, mangoes (8-15 m high);
- oranges, grapefruit, limes paw-paws (5-10 m high);
- bananas, plantains (3 - 8 m high);

arable crops

- yams (3-6 m high);
- maize (1.5 - 2.5 m high);
- cassava, cocoyams, pepper etc. (1-2 m high);
- groundnuts, melons, vegetables (0.1-0.3m high);

Various trees form the upper part of the storey whereas arable crops (food crops, H.B.) grow under the shade of the trees. The leaf canopy becomes denser the closer it is to the ground, and hence it

- reduces erosion by absorbing rainfall,
- shades the land and so reduces soil temperature,
- provides a leaf litter for nutrient recycling,
- maintains reasonable levels of organic matter and
- conserves soil moisture during dry periods." (Lagemann, J., 1977, p. 32)


The land-use system of multi-storey cropping closely resembles the natural vegetation of the forests and tree savannahs. Apart from the advantages mentioned above it has the following:

- There are always leaves to convert the energy of the sunlight into plant food. Light is used by leaves at various levels of the multiple storey system.
- "Growth of weeds is suppressed by the close cover of the leaf canopy." (Lagemann, J., 1977, p. 135)

- The roots of the various plants making up the multi-storey system reach different depths. A root system like this can absorb moisture and nutrients effectively. Also, nutrients supplied by chemical or other fertilizers are used efficiently due to the dense root system.

Because of their deep roots, trees have been termed "nutrient pumps" in this and related systems of farming. In fact their roots reach down much deeper than those of the food crops. They tap water and nutrients inaccessible to the annual plants. They use these nutrients to grow leaves and fruits. A large proportion of the water they use evaporates into the surrounding air, thus creating an environment favourable to the growth of other plants. Finally, leaves and fruits decompose on the soil and release nutrients to the top soil which would not have become available without the trees. Since they take nutrients from deep down and add it to the top soil in the form of fallen leaves, twigs and fruits, they have been called "nutrient pumps".

A word of caution is in order, however. Neither the system described here nor any other new farming systems of the lowland tropics have yet been extensively tested. In particular, the economics of the various systems have not been worked out. "Nothing is as yet known about costs and returns under the conditions of practical farming." (Lagemann, J., 1977, p. 134)

4.2.4 Eco-farming

Eco-farming is a shorthand expression for ecological farming. Here the term to be explained is "ecological". It comes from "ecology". Ecology is the science of the way plants and combinations of plants adjust to their environment and finally form a stable system if they are left undisturbed. It is a special branch of biology. Ecological farming starts from the. idea that most geographical zones with their climatic and soil characteristics sustain a natural vegetation producing a relatively large amount of plant materials, and that this natural vegetation continues to thrive indefinitely, without any such inputs as chemical fertilizers and insecticides. Is it possible to farm in such a way that the natural conditions, i.e. conditions undisturbed by human activities, are preserved as much as possible? The proponents of eco-farming are positive about this. Their main concern is to maintain the productivity of the farmland. They reject farming systems which, with the help of current, advanced farming methods, produce high output but at the same time tend to destroy the productivity of the "natural" setting. Destroying the natural fertility means that - unless large quantities of inputs are supplied, production will drop drastically. High-yielding varieties depend on fertilizer, insecticides, mechanical or chemical weeding, and the right amount of water at the right time in order to realize their potential fully; the desired level of production can only be reached if increasingly large amounts of such inputs are used. As insect pests, bacteria, and viruses become gradually resistant to farm chemicals, more powerful chemicals have to be used in order to keep them in check.

Keeping up the productivity of an environment means, among other things:

- Maintaining and/or building up soil fertility;
- controlling erosion;
- breeding and/or selecting varieties resistant to climatical hazards, pests, and diseases;
- maintaining a good water-level.

A stable ecological system where the natural vegetation of an area remains unchanged for very long periods of time is governed by a set of natural laws involving biology, chemistry, and physics. Maintaining and improving the productivity of a system is only possible if those laws are known and applied.

Eco-farming incorporates the principles of minimum tillage with its emphasis on erosion control, for reasons both of soil conservation and saving labour, since mechanization is not envisaged. It also includes the principles of biological farming, rejecting the unconditional use of farm chemicals. It advances recommendations quite close to the ones presented above under the heading of "farming systems of the lowland tropics", but it has a deeper insight into the biological laws and mechanisms that keep a stable natural environment going. But while the search for viable "farming systems of the lowland tropics" seems to accept traditional farming largely because the farming population cannot change their behaviour fast enough or are not willing to do so, eco-farming has a much more positive approach to traditional farming. Traditional farming is farming without machines and chemicals. The fact that it has been stable under conditions of low and medium population density shows that it respects and uses biological laws to a large extent. Therefore, traditional farming is not seen as a hindrance to progress but as a source for learning.

Learning from traditional farming from the point of view of eco-farming would mean, first of all, finding out and documenting the many successful methods used in various places. Since traditional farming has evolved slowly and without any conscious attempt at coordination, some methods are in use in one area but not in others. One such example in Cameroon is the use of tephrosia as an intercrop and a fallow crop with maize in Kom area, North-West Province. The usefulness of tephrosia for the maintenance of soil fertility and the provision of firewood is known in an area of 3 000 to 4000 square km. Documenting the more successful traditional farming methods would make them available to other farmers in distant areas, and this might lead to major progress in increasing crop yields.

It must be recognized, however, that there is a limit to the usefulness of knowledge about traditional farming. People hardly ever know the exact reasons why traditional methods work. This is all right as long as all other factors remain as they are. It is then, and only then that a farming system developed by trial and error and adjusted to the environment will continue to function without people knowing why it works.

Building on the knowledge of general laws of nature and making use of well-tested experience from similar climatic and geographical zones all over the world - in other words eco-farming - involves at present the following practices:

- The integration of trees in agriculture for the reasons outlined in the section on farming systems for the lowland tropics.
- The integration of animal husbandry not only for the production of foodstuffs like meat, milk, eggs, but also for the production of farmyard manure.
- Fodder production for the animals. Traditional grazing soon leads to erosion and uses large areas compared with growing fodder crops.

- Erosion control by living contours. On slopes, lines of trees, shrubs and tall grass are planted across the slopes. This means very little work compared with terracing, but it -has the added advantage of checking soil run-off during rains and of finally building up terraces as soil is caught in the anti-erosion lines.

- Contour planting also acts as a form of erosion control, but especially on steep slopes it is not sufficient in itself and needs to be supplemented by the erosion control measures described above.

- Intercropping or multiple cropping is retained because of its many advantages (for details see below).

- Rotation in a system of multiple cropping is a way of making multiple cropping more rational and of ensuring some control of soil pests like nematodes. Well-chosen crop rotations are a standard feature of permanent cultivation.

- Seasonal Fallow as opposed to the fallow periods of the traditional farming systems does not just mean leaving a plot without crops and allowing any spontaneous vegetation to grow. It means planting selected fallow crops particularly suited to help in rebuilding soil fertility. Often these are nonedible leguminous plants. A careful mixture of plants sown as a fallow crop would not only enrich the soil but would also kill nematodes and harmful soil bacteria.

- Weed tolerance essentially means an end to clean weeding but not to all weeding. One instance has been found in the Usambara Mountains of Tanzania, East Africa, and is described as follows "In young cultures weeds are allowed to grow in a considerable amount together with the crop. After some time, weed 'control' takes place when it is though"' to be neccessary. The weeds are germinating, but now the crops are strong enough to support themselves. The competition between these and the growing weeds . . . is balanced by the decomposition of the mulching layer." (Egger and Mayer, 1979, p. 21) According to the authors the soil bacteria make available the nitrogen which is contained in the mulching material, provided there is enough phosphate. If the soil is not too dry, weeds continue to grow and produce green manure. They must not be cut before they produce seeds. When they are dry they are left as mulch on the soil.

"Both the growing weeds and the layers of mulch result in effective erosion control . . . As a result, more water is available for the crops. Both weeds and mulches lower the daily changes in temperature in the soils, thus reducing the evaporation in a considerable measure. This system retains more water - and the water remains longer in the soil. Humus formation, nitrogen assimilation, improvement of water balance - the secret of the tremendous success of the system of weed tolerance!" (Eager, K., and Mayer, B.J., 1979, p. 21)

- Mulching.

- Composting is regarded as necessary since well-prepared compost is a better fertilizer than mulch left on the surface of the soil.
- Resistant varieties rather than high yielding varieties are what is required. High yielding varieties, up to now, have proved very sensitive to poor growing conditions.
- Limited use of fertilizer and pesticides if all the other methods which together make up eco-farming are applied properly, there should not be much need for farm chemicals.

Egger and Mayer, whose concept of eco-farming we have presented, point out that the limited use of farm chemicals (and machinery) not only happens to suit the habits and attitudes of the farming population (who simply are not used to spending much money on farming, and who would need a lot of guidance in order to apply these innovations correctly), it also takes into account the economic interest of countries that want to save foreign exchange and maintain as much independence as possible from foreign aid and foreign suppliers.

Concluding remarks: How much is known about the new approaches?

The new approaches discussed above all result from the application of modern science to agricultural problems in the tropics. It is a recent field of investigation, and none of the approaches have been really field-tested in the tropics. Zero tillage is practised in the United States of America as one variant of a highly mechanized system of farming which uses farm chemicals freely. Eco-farming has so far been tried on a experimental scale in an agricultural development project in Rwanda. Below there is an extract from a report on the project. As with the 'farming systems for the lowland tropics", the economic viability of eco-farming has not yet been investigated. But even in the field of natural sciences such as biology, soil science etc., much remains to be discovered. Nevertheless, quite a number of interesting findings are available, and we shall list certain of them in order to show some of the more promising lines of thinking and to stimulate leachers' curiosity.

4.3 Backing for the New Approaches



4.3.1 A Project on Eco-Farming

The initial aim of the project in Rwanda was to start up a dairy and the attendant veterinary service. Another dimension was soon added, the development of peasant agriculture in a country where land was becoming increasingly scarce and where erosion is a major problem.

"One of the aspects of the project . . . and which is of the greatest importance in the moor man's energy crisis' is the planting of various kinds of trees. Tree nurseries have been established in a distance of some kilometers from each other, so that they can easily be reached on foot by the local farmers, who traditionally live in individual family holdings "dans les collines", Rwanda's ten thousand hills and not in villages or towns. Each nursery produces seedlings twice a year, and 95 percent of them produce after having been replanted in the specific areas, i.e. both forest and fruit trees such as grevillia, eucalyptus, jacaranda, and papaya, coeur de boeuf, and avocadoes. The latter are of particular interest since they make an improvement of the farmers' everyday diet.

Trees are mainly grown on the family holdings of individual farmers. We learnt that a farmer, who plants 150 trees, can not only expect to supplement his diet, but after 15 years, also cut down one tree every two months without endangering the ecology, and thus solve his own energy crisis . . .

Soil quality can improve only if the right kind of mixed plant system is introduced. This is where the so-called 'planned disorder', the planting together of useful plants and weeds comes in. For the aim is to create a new balance of plants, whereby, for example, weeds are planted and left to grow profusely. They are plants that give a mass of foliage twice as great as that of 'good' plants. When cut and left to rot on the ground they can produce up to 20 centimeters of humus. In encouraging mixed cultivation the Nyabisindu experts go against commonly accepted European prejudices against planting in close neighbourhood cocoyams, cassava, soybeans, sweet potatoes etc. Whereas traditionally coffee was grown in isolation, with the soil under the trees being kept clear, in Nyabisindu an attempt is being made to grow coffee and pineapples together, using the open space between the coffee trees. The main aim is to keep the soil constantly covered, thereby preventing the loss of humidity and stopping erosion when the next rains come. And although at the time, when we visited the project, it was already well into the dry season we could see that the underlying soil was still fairly humid.

The experts prefer the growth of leguminous plants which produce a lot of foliage and up to 200 kilograms of nitrogen per ha. Fodder plants, which have a life of six years, are especially welcome during the dry season or hivernage, when fodder is scarce. And in general these plants provide much better and richer food than the poor pastures in the valley.

To a layman then, who in so many years has seen so many 'white elephants', the Nyabisindu project looks like the start of something revolutionary new. The success so far seems to be mainly due to the confidence created among the local population by the efficient and remunerative collection of milk and the veterinary service, upon which all the other activities could be built.

It also seems to reside, however, to a very large extent in the willingness of the foreign experts to learn from the local farmer. Once the innate intelligence of that farmer had been recognized it was fairly easy to 'bundle together' various findings and 'to enrich them with modern ecological findings' and 'offer them back to the farmer.' acceptance seems to have been all the more willing since those new methods were 'directly comprehensible and accessible.'

The total and continuing success, however, will only be assured, if the experts in cooperation with the farmers 'constantly integrate new findings', keep the system open." (Metier, G., 19773

4.3.2 Evidence from Research

The following findings all refer to multiple cropping. Since multiple cropping figures in all the approaches presented above, research results in this area are of considerable importance. They have been taken from a number of sources and are meant to stimulate the reader's interest.
Firstly, they show that even after only a few years of systematic research valuable knowledge is becoming available. Secondly, simple experiments on the school farm and careful observation of local farms might reveal similar things. Once one knows what to look for one stands a good chance of finding something of interest.

Yields

There is evidence that multiple cropping produces yields per hectare and per working hour that substantially exceed yields from single cropping under comparable conditions:

- In a study of three villages in Northern Nigeria the gross return from mixed cropping was 60 per cent higher than if the same crops were grown alone.

- "Tardieu and others in the wet highlands of western Cameroon demonstrated that intercropping maize, taro (Colocasia) and macabo (Xanthosoma) under both traditional and improved methods of culture resulted in improvements over single-crop cultures 303)

- A combination of three crops, millet, maize, and sorghum "produced not only higher yields but nearly doubled the gross return." (Tourte and Moomaw, 1977, p 303)

- When a certain species of beans was grown together with maize, in an experiment in the Philippines, the maize yield was greater than when maize was grown alone, and the weight of weeds decreased. (cf. Litsinger, J.A., 1979, p. 302)

"The combination of minimum tillage and intercropping seems to prevent erosion and to produce yields which are higher than from sole (single, H.B.) crops." (Lagemann, J., 1977, p. 133)

Here are a few possible reasons for the higher yields obtained from multiple cropping:

Often, the different species in a combination of plants use the growth factors of a given plot - soil nutrients, water, light - in different ways. Instead of competing with each other, one plant uses what the other crop does not need. It is quite easy to turn this into a rule for finding productive crop combinations.

Different crops use growth factors at different times. Once this is known for the plants of a particular crop combination it can be used to advantage: "Relative planting dates of the two crops (maize and beans, H.B.) influence yields of the bush beans. Bean yields were reduced from 939 kg/ha in monocrop (single crop, H.B.) to less than 400 kg/ha when maize was planted before the beans. A 15-day advantage for the beans gave the highest yields, a result confirmed by small farmers." (Francis, Flor, and Temple, 1979, p. 241)

When pigeon peas were grown with maize they grew less well in the first four months of growth than when grown as a single crop. When the maize was ripe, however, it not longer competed for growth factors. The pigeon peas caught up and produced yields comparable to those achieved under single cropping. The plot in question thus produced a full crop of pigeon peas and a full crop of maize.

Observations at the IPAR-Buea demonstration plot showed a similar pattern: two plots were planted with cocoyams. On one plot, cocoyams were planted between maize. On the other plot, cocoyams were planted as a single crop. When the maize was ripe, it was quite clear that the cocoyams in the maize plot were much smaller than the ones in single cropping. But since they had another twelve months of growth before they were ready for harvesting, one could be quite sure that the smaller ones would catch up in size with the single crop.

Summing up these findings one could say: "When the earlier component has matured, conditions become especially favourable for the other component." (Trenbath, B.R., 1979, p. 155)

- If leguminous plants are grown together with other crops, the legume gets much of its nitrogen from the nitrogen-fixing bacteria living in its root nodules. It competes hardly at all for nitrogen with the other crops. Therefore, adding a crop like beans, cowpeas, pigeon peas, groundnuts or soya beans to a crop of cereals or tubers will increase the total yield. "Intercropping leguminous green manure crops with cereals is another possible way to supply nitrogen. Agboola and Fayemi reported that yields of four successive corn crops, each of which was fertilized with nitrogen, were comparable with corn yields from a corn-legume intercrop without nitrogen fertilizer. When the corn was neither fertilized nor grown with a legume, grain yields from the fourth crop of corn were reduced to one half that of the first." (Oelslighle, D.D., 1979, p. 287)

- Some plant species seem to be able to cure nutrient deficiencies in neighbouring plants of other species, but just how this works is not completely known.

- Pests usually do not attack all the crops of a plot with multiple cropping but only one or two. The plants which are attacked are weakened and thus compete less effectively for growth factors (light, soil, nutrients, water) than before. The plants not under attack now stand a better chance of growing. They may produce enhanced yields compensating for the poor yields from the attacked plants.

Soil Fertility

Soil fertility is less threatened by multiple cropping than the proponents of single cropping usually fear. Reasons for this are:

- Plants in viable crop combinations have root systems of various depths and get their nutrients from different layers of the soil.

- The root system of the plot is denser than that of a plot under single cropping. It therefore uses available nutrients more effectively. (This is due to the fact that some soil nutrients are not available in liquid form and are therefore highly localised. Unless a root happens to come across them, they cannot be used by plants).

- When fertilizer is applied to a plot under multiple cropping, it is used more efficiently than under single cropping. Less fertilizer is lost by leaching since the total root´system goes down deeper into the soil.

- Fertilizer in multiple cropping does not necessarily lead to higher yields from all the crops: "Increasing fertility levels in two multiple cropping patterns in Costa Rica (Latin America, H.B.) caused an increase in yields of beans and corn, a moderate increase in yields of cassava, no change in soybean yields, and a decrease in sweet potatoes." (Oelsligle, D.D., 1979, p. 278)

- Soil fertility cannot be properly guaranteed by the use of chemical fertilizers alone. Organic matter in the form of mulch and compost is of great importance. Good quality humus which results from mulch and compost has the following properties:

"1. it breaks down readily to yield the available forms of mineral nitrogen, sulphur, and phosphorus, but does not decompose so rapidly that excessive losses of nutrients occur.
2. it improves the constitution of the soil, thereby improving its water retention and diffusibility of carbon dioxide and oxygen through the soil.

3. it provides food for soil micro-organisms, especially the nitrogen fixers.

4. it provides sandy soils with an improved water holding capacity thus reducing the incidence of soil erosion." (Bernet and Schork, 1979, p. 116)

Weed Control

In multiple cropping, weeds are often kept down by the dense leaf cover close to the ground of one of the crops. Egusi and other melons, cucumber, and pumpkin grown between maize or yams cover the ground so completely that weeds have not much chance. Some species of melons and related plants also release a poison through their roots which prevents other plants from germinating.

Insect Pests

Intercropping of maize and groundnuts reduced the damage caused by the stem borer to maize. The distance between plants attacked by an insect is an important factor. In a plot under multiple cropping, the proportion of maize plants attacked by the stem borer was smaller when the plants were further apart.

"Because of severe insect damage, cowpeas are seldom planted as a sole crop in Northern Nigeria." (Litsinger, J., 1979, p. 302)

- Where there is a mixture of crops, the tall plants tend to obscure the short ones and make them invisible to insect pests.

- Plants other than the ones attacked by a given insect pest may either attract the pest and thus protect the other plants, or may actively repel them. Thus, some plants drive insect pests away by releasing some kind of poison into the air.

- Plant combinations provide more cover for predatory insects that feed on insect pests (spiders etc.)

Soil Pests

- Certain plants - crops or weeds - release chemicals from their roots that repel or kill nematodes. One of them is marigold (tagetes), another one is crotolaria. In the Usambara Mountains, there is a common weed that also seems to kill nematodes.

- In many areas farmers know of plants that "clean the farm". Schools should document these plants and try to find out what effect they really have.

The effect of plant-produced chemicals

As 'mentioned above, some plants release chemicals through their roots into the soil. These chemicals not only influence soil pests, they may also affect other plants. In some cases they prevent other plants from growing, in other cases they stimulate growth. Little systematic knowledge is available to date. Some species of eucalyptus and of the cucumber family (to which melons etc. belong) are known for effects of this kind. It would seem that there is a lot of opportunity here for plant breeders. Once such characteristics are known they can be reinforced by selective breeding.

4.4 Suggestions for school activities

Since new approaches to farming have not yet become an established practice, teachers cannot rely on mere classroom teaching to transmit them to their pupils. On the other hand, there are no model farms for teachers to turn to for observation. The best method of teaching therefore seems to be the experiment. Experiments can be done on comparatively small plots on the school farm. (For details on the experimental method see the section on experiments, vol. I, p. 82). Here are a few suggestions for experimentation:

- Experimentation with various patterns of mixed cropping:


Select two crops (e.g. maize and beans) to be grown on the same plot. Grow 5 rows of maize in single cropping. Then grow 10 rows, one row of maize alternating with one row of beans. Finally, grow maize and beans in the same row, one row using the standard planting distance for maize but replacing every other maize stand by beans, and one row following the traditional method of planting.

- Experimentation with planting times in intercrops:

Select two crops to be grown on the same plot, e.g. crop A and crop B.

a) Plant crop A 2 weeks earlier than crop B.
b) Plant crop A 1 week earlier than crop B.
c) Plant crop A and B at the same time.
d) Plant crop A 1 week later than crop B.
e) Plant crop A 2 weeks later than crop B.

Observe the development of the two different plant species under the five different conditions and record yields for each plot and crop separately.

- Experiment on the fertilizing effect of a leguminous crop in mixed cropping:

Plant one plot with maize as a single crop and a second plot with maize and beans as mixed crops. Repeat this on the same plots for at least three farming seasons and record total yields for each of the plots separately. At the end of the last season, you should be able to see whether yields have declined on the two plots in the same way. If yields on the plot under mixed cropping have gone down less than on the plot under single cropping, this indicates that the leguminous crop has a beneficial effect on soil fertility.

- Experiment on the effect of egusi melons or pumpkins on germination and growth of other plants:

Select a crop usually grown together with melon Or pumpkin (maize or yams). Plant three small plots in the following way: a) Plant maize or yams first. When this crop is well established, plant egusi or pumpkin. b) Plant maize or yams and egusi or pumpkin at the same time. c) Plant egusi or pumpkin first. When the seeds have germinated and are well developed, interplant maize or yams; Water the crops planted later if necessary. Observe germination of the two crops grown together, growth of the two crops, weed development for each of the plots.

- Experimentation with zero tillage:

This experiment should be done on sloping plots or well drained flat plots only. a) Till one plot according to the methods normally used on the school farm. b) Mulch one plot but do not till, and plant into the mulch using a digging stick or a cutlass. Compare yields for the two plots.

- Experiment on erosion control:

Experimentation with mulch and live terracing on slopes:
Design: Four small plots of equal size on a slope

a) No erosion control measures, the crop or its residues (stalks, leaves) are left on the farm.
b) Heavy mulching- with grass and crop residues as an erosion control measure.
c) Anti-erosion rows at a distance of 7-10 m. Along these rows bananas, plantains,
and/or strong, tall grass are planted.

d) Heavy mulching and anti-erosion rows as described in (c) are used as erosion control measures. This is an experiment for the rainy season. On each of the four plots, look carefully for signs of erosion. Estimate the amount of soil caught in the anti-erosion rows of plots (c) and (d).

- Experiment on the effect of shading on various crops:

Design: Two plots farmed with maize and cocoyams mixed:

a) The plot is fully exposed to the sun.
b) The plot is shaded by a light roof made from palm fronds.

Observe:

the growth of the two crops under conditions (a) and (b),
the maize yield under conditions (a) and (b),
weed growth under conditions (a) and (b),
the cocoyam yield under conditions (a) and (b)

- Experiment on the effect of thinning:

Design: Two plots of equal size farmed with maize

a) Maize is planted in rows, three to four seeds per planting hole. All the plants which come up are allowed to grow.
b) Maize is planted in rows. Three to four weeks after germination, each stand is thinned down to one plant only.

Observe:

the growth of ten to twenty stands on plots (a) and (b),
the yield per plant (number and size of maize cobs) for the ten to twenty stands selected,
the total yield of plot (a) as compared to plot (b),the average weight of a cob on plots (a) and (b)

- Experiments with weed control:

Maize is particularly sensitive to competition from weeds. The effect of weed control is therefore easy to see.

Design: Four plots and two methods of dealing with weeds: heavy mulching and weeding.

a) After germination, maize is left without weeding or mulching.
b) Maize is carefully weeded with all weeds removed from the plot.
c) After germination, the plot is heavily mulched. No weeding is done.
d) The plot is weeded at the appropriate time, weeds are left as mulch and more
mulch is added.

Observe:

plant growth on the four plots. When do differences in height and colour become marked?
growth of weeds on plots (b), (c), and (d) yields from the four plots.

- Experiments with burning when a plot is cleared:

The effect of burning is controversial. Crops grown on the plots of this experiment should include crops that do particularly well after burning.

Design: Three plots all planted with a crop combination that includes a crop responding
favourably to burning.

a) The plot is cleared and the grass and crop residue are burned on the soil.
b) The plot is not burned. Tilling is done as usual.
c) The plot is not burned. There is no tilling (zero tillage).

Observe:

growth of the two or three crops, growth of weeds, damage done by insects and other pests, yields from the three plots.

- Experiments on insect control by certain plants:

Some plants and flowers are known to drive away insects. If there are some in your areas, do the following experiments:

Design: Two class plots farmed with a crop usually attacked by insects (borers, weevils).

a) The crop is farmed as usual.
b) Plants known to drive away insects are interplanted with the crop.


Observe:
growth of crops, signs of insect attack during growth, yield of the two plots.

Collect information, together with the pupils on plants known locally to "clean the soil" and to indicate a return of good soil fertility. Write up the findings. Collect the seeds of these plants and try them out as fallow crops.

Take a crop under single cropping and the same crop under multiple cropping, and look for insects that feed on other insects (e.g. spiders, praying mantis etc.). Also, look for insects harmful to the crops (e.g. borers, weevils, grasshoppers, locusts, etc.). Is there any difference in the number of the various insects you find on the two plots?

4.5 Some Terms Used in Connection with Farming Methods

Single cropping, sole cropping, farming in pure stand, monocropping, monoculture are all synonymous. They all mean that only one crop is grown on a given plot.

Multiple cropping

Multiple cropping means growing several crops on one and the same piece of land in one year. We distinguish between two cases:

1. Farming several crops during one year. The emphasis here is on a succession of crops:

- Successive cropping: as one crop is harvested, the plot is prepared for a new crop which is planted after harvesting the first one. This is sequential cropping involving mono cultures.

- Relay intercropping, on the other hand, means that a second crop is planted on the plot while the first one is still growing. This is also known as phased planting.

2. Growing several crops on the same plot at the same time. The set of crops grown is called a crop mixture or a crop combination. Synonyms for this meaning of multiple cropping are mixed cropping, polyculture, and intercropping.

There are several ways of arranging different crops in a polyculture or system of mixed cropping. The one most common in traditional agriculture is mixed intercropping, i.e. planting the various crops without any strict order. Beans growing from the same planting hole as maize would be an example. One method is alternate strip intercropping where rows or strips of one crop alternate with rows or strips of another crop, e.g. one row of maize with one row of beans.

Multi-storey systems

The idea of multi-storey systems is linked with the concept of multiple cropping. Storey in this context refers to the leaf canopy. If plants of the same species are planted roughly at the same time, their leaves will all spread out at roughly the same height, forming a canopy. If different species grow on one plot, they will form canopies at different heights. Single cropping always leads to one storey. Multiple cropping with crop combinations containing plants that reach different heights leads to multi-storey systems. This is particularly pronounced when trees are apart of the crop combination.

Classification of fanning systems based on the duration of farming and fallowing

- shifting cultivation (see text),
- bush fallowing,
- degraded bush fallowing permanent cultivation; synonyms are:

continuous cultivation, permanent cropping systems.

(introduction...)

There is a large number of plants known as leguminous plants. Many of them are farmed, for example all the varieties of beans, peas, and groundnuts. Some are eaten, some are used as fallow crops, e.g. tephrosia and mucuna. Some leguminous crops are trees, some are shrubs (e.g. tephrosia), some are small plants not more than 10 cm in height like the groundnut.

Despite wide differences in appearance, they have certain things in common:

1. They are able to take nitrogen, one of the most important plant foods, from the air while all other plants have to rely on nitrogen available in the soil. This has an important consequence: They do not compete with other crops for nitrogen. They even enrich the soil with nitrogen they do not use up themselves.

2. The fruit of leguminous crops is always pods. These pods contain the seeds of the plants.

3. They have tap roots which usually go down deep, some of them reaching a depth of 1.50 m.

4. Their leaves are compound leaves and consist of several small leaflets.

5. Their flowers resemble the bean or groundnut flower in shape.

How do leguminous plants manage to use the nitrogen in the air? If you look carefully at the root of a bean or groundnut you will see small swellings. They are called nodules. The nodules are filled with bacteria. These bacteria feed on sugars and starches supplied by the plant. They fix nitrogen and make it available to the plant whose roots they are living in. By living together, plant and bacteria both gain. Each of them produces something the other needs. This living together is called symbiosis. Each nodule functions for only four weeks. Afterwards, it dies and breaks open, releasing nitrogen into the surrounding soil and thus enriching it. In this way, the plant gets so much nitrogen that additional nitrogen from chemical fertilizers is not necessary.

There are two main groups of leguminous crops, those that produce mainly fat and oil, and those that produce mainly protein. Groundnuts and soya beans are grown for the oil they contain, whereas all the peas and beans supply protein.

The leguminous crops most common are beans, cowpeas, and groundouts. We shall therefore concentrate on them and leave out the rest.

Information on farming these crops is bound to be sketchy since systematic knowledge is scarce: "Generalizations on weeding, staking, earthing up, irrigation, fertilizers, labour requirements, etc. are not possible since information is only available for a few crops and only for special regions. Therefore, only some aspects of pulse (grain legumes, H.B.) growing are treated below." (Westphal, E., 1977/78, p. 65)

Teachers should rely on their own experience as it builds up over years of bean and groundnut farming.

1.1 The Bean

There are two main types of beans, the short bush or dwarf bean, and the climbing bean. Bush beans grow to a height of 20 cm, whereas the climbing varieties may reach as much as 3 m, depending on the support they have (stick, tree, maize, stalk, etc.). Bean leaves are compound leaves, each one consisting of three small leaves. Bean flowers are white or light purple in colour. Bean fruits are straight pods ending in a beak-shaped point.

Its origin is Mexico in Central America, and one can only guess how the plant first came to Africa - probably together with maize at the time of the slave trade.

Beans are a common food in most of Africa. They are usually farmed together with other crops under the system of multiple cropping. The most common crop combination is maize and beans where the climbing beans use the maize stalks as support.


Common Bean (Vulgaris)

Farming: Beans are not very demanding where soil is concerned. For high yields, the common French bean needs well-structured, rich soil unless phosphorus is supplied in some form. Since they have deep roots, they easily outlast dry periods. Some varieties of beans do not like waterlogged soil, so it is important that the soil drains well. They need full sunlight for good yields and must therefore not be shaded. But the soil temperature must not exceed 30 °C. If the soil gets any hotter, the nodules where the nitrogen is fixed no longer work properly. This means that a high plant density is required so that soon after germination the soil is well covered by the leaf canopy. When preparing the farm, light tilling is all that is needed. If beans are grown as a single crop, the following spacing is recommended:

For bush beans: 30-45 cm between rows, 30 cm along the rows. This leaves an area of 0.09 m2 to 0.135 m² per plant. Plant population per hectare could go up to 150 000 plants which is 15 plants per m².

For climbing beans: If planting is done on hills or mounds, the mounds should be 90 120 cm apart. Four to six seeds are planted in each mound. After germination, the number of plants should be reduced to three or four by thinning. If planting is done on the flat, the rows should be 90-120 cm apart, and the seeds spaced at a distance of 1530 cm along the rows. The seed rate will vary from 25 to 80 kilos per hectare, according to the planting distance used.

Weeding is not much of a problem since the crop forms a thick cover preventing most weeds from growing. If climbing beans are grown as a single crop they need staking just like yams.

Fertilization is unnecessary. Leguminous crops seem to be very efficient in extracting nutrients from the soil in addition to the fact that they are nearly self-sufficient in nitrogen.

Harvesting depends on how the local population eats the bean crop. Most of the time the dry pods are collected and the grains stored for consumption. Beans are ready for harvesting (dry pods!) 10 - 12 weeks after planting.

1.2 The Cowpea

The cowpea is also known as the black eye pea. Like the bean it is an annual plant, although some varieties are biennial. There are. many varieties, some of them spreading, some creeping along the ground, while some grow up straight, reaching a height of 15 - 80 cm. The compound leaves consist of three small leaves. The flowers are 2 - 3 cm long, their colour varying from a dirty white to violet. Cowpea pods are straight with a beak-shaped point, and can be up to 20 cm long.

The crop's origin is most probably West Africa where wild varieties were found.
Cowpeas are grown with other crops in multiple cropping. They grow together with maize. During the dry season they are often found as a single crop on ridges.


Cowpea

Farming: Cowpeas grow well even in poor soils. They can tolerate slightly acid conditions. Like beans, they resist drought periods because of their deep roots. Only light tilling is needed. There are widely divergent recommendations as to planting distances:

- 2 m x 2 m,
- 90 cm - 180 cm along rows with 3 seeds per hole,
- 50 cm x 50 cm on small mounds,
- 15 cm - 25 cm along the row with the rows 75 cm to 90 cm apart.

Teachers would have to experiment in their particular area. One starting point certainly is the average planting distance used by local farmers. Sometimes, seeds are broadcast at a rate of 20 to 40 kilos per hectare. This leads to plant densities of up to 150000 plants per hectare.

The plant densities for the spacings shown above can easily be calculated. The planting time is usually the beginning of the rains or 1 to 2 months before the end of the rainy season so that the flowers are not damaged by the heavy rains.

Harvesting extends over a long period since the pods do not mature all at the same time. If the ripe pods are left too long, they dry up completely, open up, and scatter the grains. Therefore, repeated picking is necessary in order to avoid heavy losses.

1.3 The Groundnut

Groundnuts or peanuts are the most important fat producing leguminous crop in the tropics, yielding a total annual harvest of roughly 13 million tons of unshelled nuts. They are mainly grown as a cash crop for industrial processing into oil, much less for direct consumption. In 1971, India produced about 31 per cent of the world groundnut crop. In Africa, the most important producers are Nigeria, Niger, and Senegal. In Senegal, groundnuts are the only cash crop. At times, they took on so much importance that the economy of the country depended on the world market price of that one crop. In 1972, Senegal exported 230000 tons of groundnut oil and 331000 tons of the residue called "cake".

The groundout is a relatively small herb, its height varying between 15 and 60 cm, de- pending on the variety grown. Some varieties grow as a bunch like the bush beans, some are creepers, developing long stems that trail along the ground. Groundnuts have compound leaves consisting of two pairs of little leaves. They develop small yellow flowers. The most peculiar feature of the groundnut is the fact that the fruit develops below the surface of the soil. When the flower has been pollinated, a thin stem grows down towards the soil and penetrates the surface. Only after reaching a depth of 10-15 cm will the fruit start to form. If the thin stem cannot penetrate the soil there will be no fruit.

The pods are round and contain between I and 6 seeds. They are ready for harvesting 13 to 20 weeks after planting.

The plant originated in Latin America. Brazil, Peru, and Bolivia are all mentioned as countries of origin. Therefore, historically the groundnut, too, is linked with the intercontinental slave trade which followed the discovery and colonization of America by the European powers.

Groundnuts are farmed nearly always in multiple cropping with maize or yams, but occasionally, depending on soil fertility and availability of water, groundnuts are grown in pure stand.


Groundnuts

Farming: The groundnut is a plant which needs high temperatures for germination and good growth. On the other hand, it does not need much sunshine. Therefore, it is particularly well suited for multiple cropping under maize or tree crops. As groundnuts rapidly develop deep roots, they can easily cope with drought. In areas with more than 1000 mm of rain per year, drainage is important since water-logged soil is a great danger. Farming on ridges may be necessary to improve drainage. One would always have to pay attention to the problem of excess water. Groundnuts need light, well-aerated soil. Soil that bakes hard in the sun prevents the fruit bearing stems from going underground. The plants cannot tolerate acid soils. Nitrogen fixation is usually very effective so that the use of nitrogen fertilizers is not necessary. Only light tilling is required. It should not be deeper than 20 cm. Recommended planting distances for single cropping and planting in rows are:

distance between rows

60 cm

30-45 cm

distance within rows

15 cm

7.5 - 10 cm

The latter recommendation will result in a much higher plant density than the first one. Planting distances also depend on the growth patterns of the groundnut variety planted. Bunch types can be spaced closer than creeping types. As a general rule, a high plant density, providing a dense ground cover, is essential for a good crop. 100000-125000 plants per hectare, which is 10-12 plants per m2, is an acceptable density.

The seeds are planted at a depth of about 5 cm. Going deeper unduly weakens the young plants. Planting time is in March/April, at the beginning of the rains. In some West African countries, e.g. Senegal, farmers use small animal-drawn sowing machines to achieve regular spacing in straight or contour lines.

Weeds during the early stages of growth greatly reduce yields. Therefore, weeding should be done twice during the early growth period. When the plants flower' a good groundnut crop should cover the soil completely and prevent any further weed growth. Mechanical weeding at or after flowering will damage the plants.

If fertilizer is applied at all, single superphosphate should be given before planting. The exact rate will have to be determined by the local agricultural extension service.

Harvesting requires much labour. The plants are cut at the root and lifted from the soil. They are left to dry for at least 10 days, after which the pods are stripped from the stems and again dried. Unless the pods are really thoroughly dry they do not store well and may become toxic. Once they are well dried they may be stored shelled or unshelled.

Pests and diseases: Insect pests are of minor importance where groundnuts are concerned. On the other hand, groundnuts suffer heavy attacks from a virus, resulting in rosette disease. There is no cure to the disease, but current experiments in plant breeding have produced a few varieties which are immune to rosette disease.

The groundnut has many uses. The most important one is cooking oil, obtained by crushing the nuts. The residue from this process, called, "cake", is used as animal feed. But groundnuts are also eaten roasted or salted. Groundnut butter is used in cooking as well as for spreading on bread. Teachers may discuss the use of groundnuts in local foods. Groundnuts have a dual nutritive value: they contain a very valuable plant fat and high quality protein, so that they complement very well the otherwise starchy diet based on cereals or root and tuber crops.

(introduction...)

Starch is one of the three most important human foodstuffs (the others being fat and protein), supplying the bulk of the energy needed to keep the body working. An intake of 400 to 500 g of starch daily is sufficient to keep a person healthy. Starch is formed in most plants as a result of a process called photosynthesis. It can be stored in seeds, fruit, stems or roots, but the plants which are farmed for food are those which store starch in their seeds, roots, or tubers. Cereals are plants which store starch in their seeds; root and tuber crops store starch in swollen roots or specially formed tubers.
We shall devote one part of this section to cereals, the other one to root and tuber crops.

2.1 Cereals

All cereals are cultivated grasses and are grown from seeds. Most of them are annual plants. The seeds are grains of various shapes and sizes. Just compare a grain of maize, a grain of guinea corn, a grain of pearl millet, and a rice grain: guinea corn might grow 6 m tall, maize usually grows taller than a man, whereas upland rice remains rather short. Since they belong to the grass family, all cereals are somewhat similar in structure. They have a shallow rooting system. Only drought-resisting varieties have roots which go down deeper. One or several round stems grow up from the roots without an branches. The stems are divided into sections by "nodes". The sections are called "inter" nodes". The leaves grow out from the stem. They consist of a sheath that covers one internode tightly. From the upper node of the internode, the long, narrow, free part of the leaf branches off. The composite flowers form panicles (rice, millet, sorghum) or ears (wheat, rye, barley). Maize is an exception because it has both panicles and ears. But the maize ear is so different from other cereal ears that is has a name of its own, the cob.

Cereals are by far the most important staple food in the world. Only in the humid tropical areas of Africa, are cereals replaced by root and tuber crops as the staple food. In Asia, rice is the main crop in the humid tropical areas.

Crop

World Production in Million Tons

Total Area in Million

Main Producer Countries



(1975)

Hectares (1975)

Maize

323

115

USA, China, Brazil, South Africa

Rice

344

141

China, India, Indonesia, Bangladesh

Sorghum (Guinea Corn)

54

45

USA, India, Argentina, Nigeria

Other Millets

47

71

China, India, Nigeria, USSR

Wheat

355

228

USSR, USA, China, India, Canada

Source: adapted from Musaers, H., 1977, table 1, p.2

It does not seem that cereals are better for human beings than roots and tubers. It is true that, on average, they contain more protein than root or tuber crops - in fact, cereals account for half of the protein which human beings need. But the protein content of the root and tuber crops can be increased by selection and breeding. The main advantage of cereals is that they can be stored much more easily than root and tuber crops.
World production of the major cereals increased dramatically between 1962 and 1972, as can be seen from the diagram above.


World Production of Maize, Rice and Sorghum (adapted from Rehm, S. and Espig, G., 1976, table 2, p. 17)

2.1.1 Maize

The maize plant belongs to the tall cereals. There are two main types of maize, Dent Maize and Flint Corn. Dent maize ows its name to the fact that the ripe, fully dry grain has an indentation which makes it look like a horse tooth. The grains contain soft starch particles which are not very densely packed. This results in shrinkage of the starch within the outer layer of the grains. The grains are thus characterized by a dent at the outer end. The cobs and grains are generally large.

Flint corn produces very hard grains with a shiny surface. The grains are often flattened and strongly coloured. When broken they look like small pieces of flint.


Maize

Like all cereals maize is propagated by seeds. Unlike root and tuber crops it cannot be propagated by cuttings. The seeds or grains develop from the maize flower. Maize has two types of flowers. When the maize plant has reached; full size a tassle or panicle grows on top of the maize stalk. This is the male flower. It cannot produce grains but only pollen. In the axils of the leaves cobs develop which are surrounded and covered by shucks or husks. These are the female flowers on which the grains will grow later on. From the small cobs hang the stigmas of the female flowers, known as silks. Clouds of pollen fall from the tassles when the maize plant is shaken, some of the pollen sticks to the stigmas, and the female flowers are then pollinated. The male flowers mature before the silks. This avoids self-pollination and ensures cross-pollination.

Maize develops only shallow roots and is therefore very vulnerable to lack of water and to strong winds. Out of a sample of a hundred maize plants examined at a research station, 70 were found to have roots reaching 10 cm into the soil, 24 had roots reaching down to 50 cm, and only 6 had roots reaching below 50 cm. As the plant grows taller, the first one or two nodes above the ground grow adventitious roots. These roots are short and thick and attach the plant to the soil.

Maize has a similar nutritive value to the yam in that it consists mainly of starch. But is has a higher protein content and even some fat. However, the proportion of the three foodstuffs varies from one kind of maize to another. Some special varieties have a protein content as high as 20%, while in others the starch is partly replaced by sugar.

Origin: Another name for maize is "Indian corn", and Indian here means American Indian. Maize was probably first grown in Guatemala or Mexico. These are countries in tropical Latin America. Some people believe that it was introduced to Africa by the Portuguese in the 16th century. By that time, the Portuguese were trading along the West African and Central African coast and were shipping large numbers of Africans as slaves across to their American colonies.

Farming: Maize does not make very high demands on the soil. Under favourable climatic conditions where the soil has been well prepared, maize will do well in any soil except cold, moist clay or very light, sandy soil. Where the rainfall is heavy, good drainage is important. As far as climate is concerned, maize needs a lot of sunshine and warmth. It does not do well in the shade. It is very important for maize to get enough water during the period of early growth and flowering.

Tilling: On light, well drained soil, maize can be planted without any tillage. On slopes or on poorly drained soils, planting on ridges, mounds or heaps is recommended. If maize is planted in rows on the flat, tilling can be limited to the narrow strips where the seeds will be put in.

Planting: The planting distance for maize depends on the fertility of the soil, and on the water supply. The more fertile the soil and the more water is available, the closer the plants can grow together. Under multiple cropping the planting distances for maize need to be a bit larger than under single cropping. The recommended average crop population lies between 40 000 and 60000 plants to one hectare (4-6 plants per m2) with the following spacings possible:

Distance Between Rows

Distance In Rows

Plant Population per Hectare

60 cm

25 cm

66600

60 cm

30 cm

55550

75 cm

25 cm

53300

75 cm

30 cm

44400

80 cm

25 cm

50000

80 cm

30 cm

41600

100 cm

30 cm

33300

100 cm

50 cm

20000

Each planting hole or stand takes two to three seeds. 20 to 30 kg of seed will be needed per hectare. The holes should be about a finger's depth so that the seeds are between 5 and 10 cm deep in the soil. Seeds germinate after 4-5 days. Two weeks after planting, the maize should be thinned to one or two plants per hole. This should be done just after it has rained or when the soil is still very damp.

Weeding: Weeds are a greater threat to the maize crop than pests and diseases. Maize plants can tolerate competition from weeds for about 10 days after planting. Weeds that germinate one month after the maize is planted or later will not do much harm. Usually, two weedings are necessary, early weeding 10 days after planting, and late weeding 30 days after planting. Because of the importance of weeding quickly and on time, this is the most important step in farming maize.

Earthing up should be done when the plants are over 30 cm tall. This will encourage the growth of adventitious roots (or prop roots).

Manuring/Fertilizing: Compost is rarely used for maize. In most maize-producing countries, the dry maize stalks left on the farm are much more important than compost. But it is heavy work to till them into the soil.

Green manuring with Mucuna or Tephrosia could also be tried. If chemical fertilizer is used, a compound fertilizer - N.P.K. 20-10-10 at a rate of 100 kg/hectare - seems to be appropriate in the grassland areas. Fertilizer should be applied twice, once during early growth, and once when the tassles show. Each time, one gramme should be given to each plant. One gramme of fertilizer is what will go into one beer bottle top.

Harvesting: Maize is ready for harvesting 14-20 weeks after planting, i.e. roughly three to four and a half months after planting. The high yielding varieties may take even longer. This long growth cycle has important consequences for school farm work: Maize planting during the second term, usually in March, should be done as early as the rainfalls permit. Even so the crop will be ready only towards the end of July. Farm-masters and headmasters will have to make adequate provision for harvesting, drying and storing the maize during holiday time. This is the more important as the maize planted in March must not be left on the stalks during rainy season.

Signs of the getting ripe are when the silks dry up and when the leaves and shucks turn yellow.

Yields differ markedly according to variety and planting time. The following table summarizes a few figures on maize yields.

Yield (kg/ha)

Remarks

2800

world average

1350-2240

west Africa, early maize, weight after drying

750-1120

west Africa, late maize, weight after drying

5000-8000

normal yield for maize in the tropics

20000

maximum yield with careful fertilizing very good insect, pest, and weed control, and high yielding varieties

Newly harvested maize may lose as much as 20% of its weight when dried. Weighing should therefore be done after careful drying.

Pests and Diseases: Seed rot is caused by fungi. The seeds may not germinate at all or the seedling may die shortly after germination. Seedling wilt is also caused by fungi. It starts with a grey mark at the tip of the leaf, and within one or two days the seedlings wilt. Maize rust affects the leaves and causes a conspicuous light colour in the centre of the leaves. Stalk rot causes the plants to mature too early, and therefore poorly filled grains, low yields and stalk breakage. Smuts are caused by fungi. The head smut produces a black mass of spores in the male flowers and in the earshoots.

The most important insect pest is the stem borer or stalk borer. Other pests are birds, rats, millipedes, aphids, and armyworms. Weevils may cause heavy damage to the ripe cobs.

Drying and Storage: While in store, maize is attacked by weevils and rats. If the maize is not dry enough, it may be attacked by fungi and become mouldy. Therefore, if the harvest cannot be sold immediately, it is very important that the crop be dried properly. Different types of dryers are being tried out at the moment. The cobs are stored in open cribs made from bamboo or raffia, this could also be done in airtight silos, but they are very expensive to build.

2.1.2 Rice

Rice is one of man's most important food crops. It is also one of the first plants ever farmed by man.

Rice is a very peculiar plant. Some varieties of rice grow on dry land, but some grow even when the soil is flooded with water.

And some varieties can only grow when the whole farm is well flooded for quite a long time. Rice which grows on dry land is called upland rice. Rice which grows only in water is called swamp rice or irrigated rice. Farm work is quite different for upland rice and for swamp rice. There are very many varieties of cultivated rice, which makes is possible to grow the crop in widely differing soils and climates.

The main rooting system develops from nodes below the ground. When the heads or panicles grow, there is a matted mass of roots near the surface of the soil. With swamp rice, this mat of roots is often covered with green algae, and it is believed that this helps the plant to breathe. When the roots are firmly established, the plant tillers, that means that it develops several stems each with seed bearing heads instead of only one. The stems are erect, cylindrical, smooth, and hollow except at the internodes. They terminate in a branched, open panicle. Varieties of rice vary in height from 30 cm to 1.80 m. The growth cycle from germination to maturity depends mainly on the variety, but climate, too, has some influence. Some rice varieties get ready for harvest in four months, others take six months. Rice has small green flowers which are self-pollinating. The small fruits are pointed at each end and are covered with a strong seed coat or husk. They grow on the panicles. Generally, one month after flowering rice is ripe and ready for harvesting.


Rice

Origin: Rice has two areas of origin, one is Asia, and the other is West Africa. The Asian varieties of rice have white grains. In Asia, rice is the single most important cereal. In China, Asia's largest country, rice has been farmed for at least 5000 years, and in India, books written 3 000 years ago already mention several varieties of rice. Even now, Asia is still the most important continent for rice farming. It produced 266 million tons of rice in the early seventies, this represents more than 90 % of the total world harvest. Here are the main producing countries in Asia:

Country

Harvest (million tons)

China

104

India

58

Indonesia

18

Japan

15

Bangladesh

15

Thailand

12

Other Asian Countries

44

Total

266

But rice farming in West Africa also has a long tradition. It originated in the interior delta of the river Niger, in a country which today is called Mali, around the towns of Mopti and Timbuctu. African rice has yellow, reddish, or brown grains, and there are both upland and swamp varieties. From its area or origin, the African rice spread towards the west, and rice farming in Senegal and the Gambia may date back as far as 1500 years B.C. From the time of the first contacts between Europeans and Africa, Asian rice was gradually introduced to West Africa. Throughout the 15th, 16th, 17th and 18th centuries, new varieties of rice were grown along the West African Coast and slowly found their way into the hinterland. Asian rice was not grown on a large scale in Africa until after 1920. But already between 1800 and 1850, white-grained rice had been found right in the old area where African rice came from, in the interior delta of the river Niger.


Growing Area of African Rice Varieties (adapted from Mohr, B., 1969, p. 28)

Upland Rice Cultivation: Upland rice is grown on the light soils of the open savannah and does well even on steep, stony slopes of hillsides provided its requirements of water (800-1500 mm annual rainfall) are met. Traditionally, it is cultivated under a system of shifting cultivation on a newly cleared piece of land. For details see part I on Farming Methods.

The plot where the upland rice is to be farmed is tilled lightly after clearing and burning have taken place. The seed is sown broadcast at the beginning of the main rains. Weeding is done shortly after germination, and later on as required. One of the main problems in rice farming is the damage done by birds. It is usually the children's job to scare birds away from the time the rice heads have formed until the harvest. Often, a raised platform is built at one corner of the field, and from it ropes are stretched all over the field. Things that make a noise or odd movements are tied to these ropes and scare away the birds when the ropes are pulled from the observation platform. When the time comes to protect the rice against birds and other animals, school classes lose many of their pupils!

The Agricultural extension agents give the following advice for farming upland rice:

The soil should be tilled 15 to 20 cm deep. Planting should be done in straight lines. This will make weeding easier. The distance between rows varies between 25 and 40 cm, the seed rate varying between 100 and 30 kg per hectare accordingly. Along the lines, seeds are planted at intervals of 1 - 2 cm. In order to save work, lines can be drawn by using a marker (which can easily be made from bamboo or raffia).

The seeds are planted 2-2.5 cm deep and then firmly covered with soil.


The Marker (adapted from FAO-INADES, Upland Rice, 1979, p.5); Sickles Used for Harvesting Paddy (adapted from Presbyterian Rural Training Centre, undated)

Fertilization: High yielding varieties especially need chemical fertilizers in order to produce really high yields. The first application of fertilizer is done one month after planting. A compound fertilizer NPK 20:10:10 is used at the rate of 200 kg/ha. The second application follows two months after planting. This time, urea is used at a rate of 50 kg/ha. Fertilizer is always applied along the rows.

Harvesting and Threshing. Harvesting is done 15 to 25 weeks after sowing, depending on the variety. This involves cutting the whole rice plant at the base with a special knife called a sickle. Cutting the rice should start early in the morning, so that threshing can be done around 11,00 a.m. when it is getting hot and dry.

Threshing, i.e. removing the seeds from the heads, must be done immediately after harvesting, because upland rice is already very dry at harvest time, and the seeds would soon fall off by themselves. Threshing can simply be done by gathering a handful of rice and gently beating the heads on a log of wood so that the grains fall off. But there are also simple hand-operated machines for threshing. Yields for upland rice vary between 900 and 1700 kg/hectare. Under very good conditions, one might get 3 tons (3000 kg) per hectare. This is the paddy yield, i.e. seeds covered by their husks.

Labour Estimates Agricultural experts at W.A.D.A. (Wum Area Development Authority) have estimated that upland rice farming, if done by manual labour alone, requires 90 days of labour per hectare. This includes all the labour needed for land preparation, weeding, fertilizing, bird watching, harvesting, and threshing. Diseases and pests are the same for upland and swamp rice. They will therefore be discussed later.

Swamp Rice Cultivation: While upland rice farming does not require more skill than maize or yam farming, swamp rice farming is a very skilful activity. Swamp rice fields need careful planning and upkeep. They have to be prepared in such a way that the water level in the field can be controlled at any time. This means building irrigation and drainage canals.

Of course, swamp rice could also be grown in natural swamps or fresh-water mangroves. But here the water level cannot be controlled, so that the crop is much more exposed to climate hazards then in artificially prepared rice fields. Swamp rice has three principal advantages over upland rice:

1. Crop failure due to drought or badly distributed rainfall is almost eliminated;
2. Yields are consistently higher;
3. Soil fertility is maintained and continued cultivation on the same plot is feasible.

Why is it so important always to control the water-level in a rice field? In order for rice to yield maximum crops, the water level should be as follows, due to the water requirements of the plant as it grows:

At planting and up to 6 to 8 days afterwards the water should not be visible, but the plot should be covered by liquid mud. Under these conditions, seedlings transplanted from their nursery will easily establish firm roots.

After this, the field should be flooded to a depth of only 2-3 cm. This level should be maintained for 45 days (1,5 months). During this time, the seedlings tiller: one plant develops several stems all of which will later form their own heads or panicles.

Two months after transplanting, the water level should be raised to 10 cm and kept there for another 5 weeks. From the time the panicles or heads have formed until they start turning yellow, the rice field must always be flooded. It should stand in about 20 cm of water.

Afterwards, i.e. about 17 weeks or 4 months after transplanting, the water level should go down gradually.

Ten days before harvesting, the water should be drained away completely.

In natural swamps such as can be found in the wide valleys of big rivers, a long and heavy rainy season produces a natural rise and fall in the water level, and this is indeed the environmental condition to which wild swamp rice has become adjusted. If in such swampy areas the water starts rising shortly after the heavy rains have set in, goes up to a certain height and then gradually goes down again towards and after the end of the rains, why should farmers bother to lay out special rice fields where they can control the water level at will?

1. The rains might fall unevenly throughout the rainy season so that the height of the water level does not match the development of the rice plants.

2. The rains might stop too early or too late. In both cases, the harvest will be less than expected or might be lost altogether.

3. There are areas which are not regularly flooded but which have a stream nearby that could ensure an adequate water supply. Such areas can be irrigated, i.e. artificially provided with the water necessary for rice farming. Thus irrigation enlarges the area suitable for swamp rice cultivation.

4. With enough water available from a stream or river, a second or third rice crop can be grown during dry season. This has the same effect as if the area under rice had been doubled or tripled. It should be clear by now how important it is to lay out rice fields which can be flooded and drained at will.

Planning and Opening up a Swamp Rice Field: Planning a swamp rice field requires much thought, skill, and experience. The area to be flooded must be level. Only then will all the plants have the same depth of water. Steep slopes cannot be used, but gentle slopes can be. A plot with a gentle slope must be subdivided into "checks" marked off by small dams called "bunds". Inside the checks, the ground must be levelled.

Where there is no traditional knowledge about farming swamp rice one should be sure to consider all the important points in order not to make mistakes in the layout.

Digging irrigation and drainage canals, building dams and the first clearing all are very heavy work' to be done at the very beginning. Planning at the beginning has to be very thorough in order not to waste this effort. In any case, an adviser should be called in to check before the work actually goes ahead.

The following points should be investigated before work starts:

Is there enough water available? If one cannot draw on the experience of previous years, observation should be made over at least one year. A small experimental plot would be of great help.

Is the soil suitable? Rice does not make heavy demands on the soil; as long as there is enough water, it will grow. Pure sand and pure laterite soils cannot hold water and are therefore unsuited for rice farming. Simple soil tests should be made all over the plot intended for rice farming. A hand test of the soil structure will be sufficient.

Can the plot be levelled without too much effort? If has to be levelled because there must be the same depth of water all over. The more small hills and depressions there are on the plot, and the more it slopes in one direction, the more levelling and building of bunds will have to be done.

Clearing the Plot: Plots overgrown with grass and small shrubs do not present any serious problem for clearing. When there are trees or big shrubs, they have to be cut down. Small stumps should be uprooted and the big ones left to decay in the field. If there are big trees, it is advisable to kill them instead of cutting them down.


Irrigation and Drainage of a Swamp Rice Field

It is not possible here to go into details of how to build dams and dig the canals. A few remarks is all we can provide:

1. In order to provide irrigation water a small dam will have to be built across a nearby stream, or a small river. Such dams can be built from earth and sticks. Concrete dams are better' they last longer, but they are more expensive.

2. From the dam, the main irrigation canals are dug so that they run round the upper boundary, a canal is dug through which irrigation water from the fields can flow away. This canal is called the main drain.

3. The whole area surrounded by the main irrigation canal and the main drain is subdivided into smaller plots with boundaries running at right angles from the main irrigation canal down to the main drain.

4. Exactly on these boundaries smaller canals are dug with small, strong dams at both sides. These canals serve as distribution canals and feeder drains.

5. It is these plots surrounded by the main irrigation canal, the distribution canal, the feeder drain, and the main drain that are subdivided into checks according to the slope that exists between the main irrigation canal and the main drain.

When it is time to flood a check, water is allowed into the distribution canal from the main irrigation canal. Through an opening in the small dam alongside the distribution canal, it flows into the check until the water level has reached the desired depth. When it is time to drain the water away, an opening is made in the dam of the feeder drain of that particular check, the water flows out and runs into the main drain.

Water is a main cause of erosion. Water weeds will grow in canals. Therefore, regular upkeep of all parts of the irrigation and drainage works is very important for the good functioning of the whole system.

Swamp Rice Farming and Cooperative Work: It should be clear by now that swamp rice farming is more than just growing a crop on a piece of land. Before the first rice crop can be grown, a lot of work is needed in order to build the irrigation and drainage system. And over the years, this system has to be kept in good order, otherwise there will be no harvest.

Where several farmers in one area grow rice, they will not build individual irrigation and drainage systems. It would not be possible, and even if it were technically possible it would be too costly. Rather, farmers using water from the same source will join forces to build a common irrigation and drainage system: one dam to store irrigation water, a few main irrigation canals and main drains. Once this system has been built, there is need for a joint effort to keep it in good condition. It would be unfair to ask one man to look after the dam since all the farmers profit from it. Furthermore, if a farmer does not maintain the main irrigation canal or the main drain supplying his fields with water the other farmers will suffer.

Swamp- rice farming therefore inevitably leads farmers towards joint effort or cooperation. And because they learn to join hands in order to carry out farming, it should be easy for them to raise money jointly in order to buy a rice thresher and a rice huller.

The Nursery: Unlike upland rice, swamp rice cannot be sown straight into the future rice plot. There would be too much loss. Rather, nurseries are made and young rice plants are transplanted from the nursery into the field.

The soil of the nursery must be rich and of a good structure. Poor or too heavy soil should be manured with compost. A nursery can be made on one of the checks in the rice field, or close to the house. If the nursery is near the house, it is easier to look after, but if it is on a check, less work is needed to transport the seedlings and water.

Because good growth in a nursery is so important, somebody will have to watch it in order to keep away birds, rats, cattle, goats and pigs.

The Size of a Nursery: A nursery must be big enough to supply seedlings for the whole rice field. Some of the seedlings will not be healthy and strong at the time of transplanting. It is therefore important to have more seedlings than will actually be transplanted. This enables the farmer to select the best seedlings only. It will also give him the seedlings needed to replace the ones that do not grow after transplanting. A nursery which covers one tenth (10%) of the area of the future rice field is about the right size. A farmer who wants to farm an area of 0.5 hectare (5000 m2) will have to make a nursery of 0.05 hectare or 500 m2.

Preparing the Nursery: The soil should be tilled to a depth of at least 20 cm' 2-4 weeks before sowing. It is then kept flooded, and the loose soil is worked into a fine mud which is completely level. If the nursery is big, it might be subdivided into seed beds that are 1.5 to 2 m wide and 20 cm high. This will make things easier later on, since the paths in between give easy access to all the seedlings. Before sowing, all small lumps of earth should be broken up, all hollows should be filled in and all little stones removed. If the soil of the nursery is poor, it should be enriched with chemical fertilizer where compost is not available. For each 100 m2 of the nursery, one will need 1.5 kg ammonium sulphate, 1.5 kg dicalcium phosphate, 1 kg potassium chloride. These fertilizers must be spread evenly all over the nursery.

Preparing the Seeds: Only rice grains covered with their husks, i.e. paddy, should be used for sowing. They are taken from healthy, well developed plants. If there is an Agricultural Extension Office nearby, it might be possible to buy high quality seed. Swamp rice seeds are pre-germinated. This means making the paddy grains germinate before they are sown. Pre-germinated seeds grow better and faster. Rats and birds do not like them as much as ordinary paddy grains, and so fewer seeds will be eaten.

To pre-germinate the seeds, they are first of all covered with water and left there for a full day, 24 hours. The rice grains are then taken out of the water and spread out on mats, baskets, or sacks, and covered with damp material. Within one or two days, a tiny sprout will appear, and the grains have effectively germinated. It is now time to sow them. Seeds are broadcast at a rate of 6 kg to each 100 m2 of nursery. Remember that the nursery is one tenth the size of the final rice field. Therefore, 6 kg of paddy will be enough to plant a field of 1000 m2, and the seed rate per hectare is 60 kg. The grains should be covered with very fine soil. Light mulching with rice straw and thorough weeding are important.

Transplanting: Transplanting is done 1 month after sowing. The rice field is prepared in the same way as the nursery. The seedlings are ready for transplanting when they have four or five leaves. Only strong and healthy seedlings should be used. The seedlings are cleaned from mud, the tips of the leaves are cut off, and they are tied into small bundles. This makes it easier to carry them.

The seedlings must be transplanted into mud. Planting is done along straight lines which are 20 cm apart. The planting distance along the lines is 20 cm to 30 cm. Each time, 2-4 seedlings are planted together at one spot. 6 - 10 days after transplanting, all the seedlings should have taken proper root. Those that are dying off must be replaced.

Weeding: Two weeks after transplanting, the first weeding is necessary. Later on, weeding is done as the weeds develop. Generally, if the rice field is kept well flooded, there will not be much need for weeding. But since rice is very vulnerable to weeds, careful weeding pays off by increasing the yield.

Applying Fertilizer: The application of fertilizer depends very much on the type of soil, the nutrient content in the irrigation water, and how intensive the farming is. In a newly opened field it is certainly not necessary to use chemical fertilizers. The time when such fertilizer is needed can be found out by watching the yields over a few seasons. It is, however, very important to provide sufficiently fertile soil, because the labour input is the same whether the soil is poor or rich, but the harvest will be different. Economising on fertilizer when the natural soil fertility has gone down therefore means wasting human labour. Trials have shown that nitrogen is the most important fertilizer for rice production.

Two weeks after transplanting, when the rice field has been drained for weeding and replanting, fertilizer is applied at a rate of 100 kg of ammonium sulphate for every hectare of rice field. When the panicles are forming, the field is drained again and fertilizer is applied, this time at the rate of 50 kg of ammonium sulphate for every hectare.


Special Weeding Hoe for Rice (adapted from Presbyterian Rural Training Centre, 1977)

Harvesting: It is difficult to know exactly when swamp rice is ready for harvesting. There are a few signs, however:

- The heads are yellow, although the stem and leaves might still be green.
- The grains are hard. They make a crunching noise when one bites them.

Harvesting too late might cause loss of yield since over-ripe grains will fall out before or during harvesting. Harvesting is done with a sickle after the field has been drained and left to dry for 1 to 2 weeks.

The harvested rice is tied into sheaves and kept stacked in the field to dry further. Treshing is done in the same way as for upland rice.

Swamp rice after harvest will yield one or two ratoon crops provided there is enough water and warmth. For a good ratoon crop the rice should be cut just above the roots. The ratoon crop will need 2-3 weeks less than the first crop to get ripe, and it may even give higher yields.

Yield: The average yield for the whole world is about 2.3 tons of paddy per hectare. But high yielding varieties can yield 6-10 tons/ hectare under very good conditions. Experiments at R.T.C. Kumba point to yields above 4 tons per hectare.

Processing Paddy: Paddy rice is not yet ready for consumption. It must be hulled. The husks covering the rice grain must be removed. Hulling reduces the weight of rice considerably, at a rate of about 35%. The above table of yields shows how much hulled rice one can expect for given quantities of paddy. This, by the way, is the same for upland and swamp rice.

Yields

Kg/Hectare Paddy

Hulled Rice

Very high from high



yielding varieties

10000

6500

Medium from high



yielding varieties

6000

3900

World Average

2300

1495

Poor Yields

1500



1200



1000


Hulled rice = 65% of paddy = 0.65 x paddy

After hulling, rice is often polished. This makes the grains white and shiny but removes important foodstuff like proteins. Sometimes, you will find on the market parboiled rice. This means that the paddy has been boiled briefly and dried again. Parboiling protects the rice from breaking up when it is hulled and polished and improves the nutritional value of polished rice. Parboiled rice also needs less cooking than ordinary rice.

Other Uses of Rice: But it is not only the rice grains that are useful to man. The husks removed in the hulling process are used for fuel. The bran removed when the grains are polished can be used to feed domestic animals. The rice straw itself has several uses. Immediately after harvesting, the stems and leaves are still green and are therefore valuable food for cattle, sheep, and goats. When rice straw is completely dry it is very suitable for handicrafts, e.g. for weaving bags, mats, and hats. It can even be used for thatching houses.

Diseases: Blast is a fungus disease which is very common. It is mostly found on the leaves although it may attack other parts of the plant. Small spots appear, turning grey or brown. The nodes and branches show dark rings, the heads lose their colour and do not develop. Plants infected in this way should be uprooted and burned.

Narrow brown leaf spot: Plants suffering from this fungus disease may lodge. All trash that shows signs of the disease should be burned.

Brown leaf spot: This disease affects the leaf, the leaf-sheat, and the husk of the grain. The disease can be transmitted through the seed. Seeds should therefore be disinfected before sowing.

Pests: Various borers attack the stems of the rice plants. They can be controlled to some extent by crop rotation. Also, certain bugs damage the stems, leaves, or ripening heads. Much damage is done by grain-eating birds, e.g. the weaver bird.

Improving the Rice Plant: Like maize, rice has received a lot of attention from scientists in order to improve such important features as yields, taste of the grains, resistance to pests and diseases, adjustment to different climatic conditions etc. The International Rice Research Institute (IRRI) in the Philippines has succeeded in breeding various so-called high yielding varieties which have been already mentioned in the text. They are very important since the world population is increasing, and in order to feed all of them, more food must be grown by farmers everywhere. Rice varieties from IRRI always have names starting with IR: IR32, IR42, IR442. But research on rice (and on other crops) must and can be done in every country where the crop is grown. Only then can the best farming methods be found. Even school farms can be used for this purpose. Here is a report on a trial of a particular variety done by R.T.C., Kumba, taken from their annual report for 1977:

"Wet Paddy or Swamp Rice"

Varieties: Besides our normal varieties, IR 4-2 and IR 22, the following varieties were tried out: M. 45; Tainan V; 1632; IR 32; IR 34; IR 442. Out of these varieties only one was clearly disappointing: 1632. It had poor germination, the yield was lowest and the grains were difficult to thresh. The results were obtained with the other varieties (see table below).

The figures on the yield must be taken with caution since some of the trials were only very small and none of them was repeated. New trials during the next season will have to show if the results can be confirmed.

Seed: Due to bad experience in the past we used double the quantity of seeds: for 100 m2 of field we used 1 kg of seed which was sown in a nursery area of 4 m2. All the seed was treated with Panogen 15 and pre-germinated before sowing. When transplanting 2 - 3 stems at distances of 20 x 20 cm we had a small surplus of seedlings.

Variety

Theoretical Resistance against Disease

Theoretical Time till Maturity

Our own Experience of the Time Needed from Pregermination to Harvest

Yield per ha in Paddy

IR 4-2


130 days

130 days

4 800 kg

IR 22

sensible

130 days

136 days

4 600 kg

M. 45

resistant

120 days

116 days

4 000 kg

Tainan

sensible

120 days

122 days

5 500 kg

IR 32

resistant

150 days

164 days

5 700 kg

IR 34

resistant

135 days

153 days

5 100 kg

IR 442

sensible

135 days

139 days

6 000 kg

Fertilizer: Fertilizer was given in two applications: The first, before transplanting, at a rate of 400 kg ha of 20-10-10 and the second about 6 weeks later at a rate of 200 kg per ha of 20-10-10. When transplanting is done in strips, it would probably be better to give the first fertilizer after transplanting and not before.

Planting in Strips and Weed Control: The rice was planted in strips of 4 m with a distance of 0.8 m between the strips. The single lines go across the strips. The strips were still of advantage when applying fertilizer and for the installation of bird scaring systems. The loss of area could be disregarded since the rice nearly covered these patches of ground when getting ripe.

Damage by fish: During and after transplanting the rice, the water level was unusually high and this allowed many fish from the nearby stream to enter the rice-field. These fish were observed feeding on the stems of the freshly transplanted rice and they destroyed completely two sections that were under deep water.

Damage by birds: Due to an intensive campaign at scaring the birds, the damage was estimated to be below 10%, which we consider to be a good result."

Tools and Implements Used with Rice

1. The Marker

The marker shown on p. 106 is a tool used to mark lines or rows on a farm. It is like a rake but is of course much bigger. It can be made from Indian Bamboo or from raffia. Its use is not limited to marking rows for rice planting. It can be used for any crop whose rows are less than 50 cm apart. After tilling, the marker is pulled from one end to the other and replaces ropes in the marking of straight lines.

2. The Sickle

Sickles are unknown in many African countries and the one on the left of the illustration on p. 106 is imported from abroad.

One might ask why people do not use the matches which usually serves very well when used to cut grass. The answer is simple if we remember that ripe paddy grains tend to fall off the panicles very easily. Using the matches on rice would result in heavy losses because many grains would fall to the ground. It is better to grasp a handful of rice plants, hold them firmly so that they do not shake, and then cut. A matches would be too heavy and too long for this kind of work.


Threshing Box with Threshing Ladder (adapted from Presbyterian Rural Training Centre, undated)


Threshing Trestle (adapted from Presbyterian Rural Training Centre, undated)

3. The Threshing Box and Threshing Trestle

They are shown in the illustrations on p. 115. They can be made entirely from local material, using planks, bamboo, raffia, old bags, plastic sheets, mats, or whatever is available. The measurements given are examples only, they can be modified in order to suit the people using them. The main piece is a wooden grille against which the rice heads are beaten. The grains fall off. In order to prevent the grains from spreading over a large area, the grille is surrounded by some kind of wall or screen. This keeps the grains just below the grille where they can be removed very easily.


Rice Threshner

4. The Rice Thresher

The rice thresher is a small machine. The one shown in the illustration is operated by a man or woman, just like a sewing machine. But the same model could easily be operated by a small engine. Inside the thresher there is a drum which keeps turning. On the drum there are many small loops made from wire. The man threshing the rice starts turning the drum and feeds a good handful of rice into the thresher, heads on to the drum. As the loops brush through the rice heads, they quickly remove the grains.

The thresher is expensive, however. Also, threshing box or threshing trestle. Experience has shown that one person alone finds it difficult to operate the thresher and keep feeding in the rice to be threshed. Two people are needed.


Guineacorn (Sorghum)

2.1.3 Guineacorn

Guineacorn belongs to the sorghum family. It is a very tall cereal, easily reaching 3 - 6 m in height. Like rice, it is a biennial plant so that ratooning is possible: when the stem is cut, at harvesting, the root will grow another shoot which is likely to produce as well as the first one. Guineacorn develops one big panicle. Since it grows very tall, it also develops adventitious or prop roots. The main rooting system reaches down deeper than maize roots. Therefore, guineacorn resists drought much better than maize. When a drought becomes very severe, the plant stops growing. As soon as there is sufficient water, it starts growing again.

Like maize, guineacorn does not tiller. According to the particular variety and climatic conditions, its growth cycle is between 90 and 200 days. After flowering, it takes 35 - 70 days to come to full maturity. At flowering, both self- and cross-pollination occur.

Origin: Guineacorn and the other varieties of sorghum are truly African plants. West Africa, Ethiopia, East and South Africa are said to be the home of the sorghum family.

Farming: Guineacorn adapts itself to a great variety of different soils. It accepts heavy soils which crack under the heat, it even tolerates a certain amount of acidity and salt. As mentioned above, it can do with a little bit of water. It can grow in areas with 375 to 1000 mm of rainfall per year. The optimum rainfall is 500 to 600 mm. For a short time it can endure waterlogging, the best temperature for growth and high yields seems to be 27 - 28 °C. It tolerates very high temperatures better than any other cereal and is therefore very well adapted to conditions in semi-arid climates.

Its nutrient requirements are very high, but as its root system is very efficient, it grows on poor soils. It can easily be included in a crop rotation. In forest zones it could be grown after clearing. But in savannah areas, where grasses are left to rot after clearing, it might not do well in the first year after clearing. The reason is that the decaying grass absorbs too much soil nitrogen which will be released afterwards but will not be available when the first year crop needs it most.

Tilling is done in the same way as for maize.

Sowing/Planting: Guineacorn is planted during the first rains. Planting distances vary widely according to soil and climatic conditions. The following table gives an idea of various spacings, assuming planting in rows.

Distance Between Rows

Distance In Rows

Plant Population per Hectare

25 cm

20 cm

200 000

25 cm

6 cm

660 000

90 cm

20 cm

55 000

110 cm

60 cm

15 000

60 cm

20 cm

83 000

Guineacorn seeds are planted at a depth of 2.5 to 5 cm. Depending on the planting density one would need 5 to 15 kg of seed per hectare. In some areas young shoots are transplanted after germination.

Weeding must be done early. Guineacorn does not do well if there is competition from weeds during the early growth period.

Earthing up is recommended since it stimulates the growth of adventitious roots.

Guineacorn is likely to suffer from nitrogen deficiency. Fertilization with up to 150 kg of nitrogen per hectare might be necessary, especially in the case of improved varieties. Two thirds of this quantity should be given at planting time, one third when the plants flower. The average yield in Africa is about 730 kg per hectare; the world average stands at 1200 kg per hectare. In Italy, an average production of 4400 kg per hectare is achieved, and the highest yields recorded are around 20 tons per hectare.

Pests and Diseases: Guineacorn suffers from the same diseases and pests as maize. It is heavily attacked by smuts, less severely by rust. Stem borers are a problem, but weevils do more damage. Birds are the main enemies of guineacorn. When the grains get ripe, people take turns to scaring off the birds in order to reduce losses.

Improvement: Like the other cereals, guineacorn can be improved by breeding. High yielding varieties with shorter stems and an even higher tolerance towards drought and flooding have been developed.

Guineacorn Production: Guineacorn and other varieties of sorghum are produced in relatively large quantities in Africa:

Nigeria: 3.6 million tons in 1972 Sudan: 1.4 million tons in 1972 Total Africa: 8.9 million tons in 1972

2.2 Root and Tuber Crops

Root and tuber crops are the main food of about 400 million people living in the tropics. In Africa, they provide about one third of all food. Root and tuber crops have not been improved much by selection and breeding. There is still much scope for improvement. Already now they yield as well as most cereals or grain legumes farmed in the humid lowland tropics, especially in the forest zones. Botanically, they belong to a number of different plant families. They all have underground organs, i.e. parts of the plant for storing energy in the form of starch, sometimes sugar. These storage organs may be swellings on the roots (cassava), whole underground stems or stem tubers (cocoyam and xanthosoma where they are called corms and cormels) or a portion of the underground stem as in the case of yams and Irish potatoes.

The edible roots and tubers contain much starch, little protein, hardly any fat, few vitamins, and much water. Cassava is particularly poor in protein, and if it is used as the main staple food, people may well suffer from lack of protein. On the other hand, cassava leaves are very rich in protein so that a diet consisting of garri and cassava leaf soup comes close to being a balanced diet, at least as far as starch and protein are concerned.

"Cereals contain a little more protein than most tuber crops, but in every other aspect of food quality tuber crops are superior to cereals." (Westphal, E., 1978, p. 17) Yams and Irish potatoes especially produce as much protein as some cereals.

Information on the farming of root and tuber crops is scanty. Most of them have not been subjected to intensive farming on scientific lines. Apart from traditional farming methods, there are a few rules of thumb that teachers will have to develop.


Yams

2.2.1 Yams

Yams belong to the forest fringes and the open savannahs rather than the more humid areas, although there are varieties that are very well adapted to high humidity. There are very many cultivated varieties. In Eastern Nigeria and in many parts of Cameroon, yams are appreciated as high quality food and fetch good prices.

The Plant: The yam is a climbing plant. Its root system is rather weak. The yam tubers are large underground stems varying in number, size, and form according to the variety. There are "eyes" on the tubers, buds from which shoots grow when the right conditions prevail. Some varieties produce one tuber, others two or three. Some tubers are round and long, others may branch out and take curious shapes. If the yam is not harvested it is a perennial plant. The stem dies off at the end of each growing season, which creates the impression of the yam being an annual plant. But the tuber lives on and grows a new stem during the next year. Yams climb by turning round a support. The stem itself is too weak to stand on its own. The leaves often have the shape of a heart and are compound leaves with three smaller leaves making up the total leaf. Yams are usually propagated vegetatively, i.e. by tubers or tuber cuttings. Therefore, people do not pay much attention to yam flowers. However, the plants produce male and female flowers separately. But whereas in the case of maize the two types of flowers are on the same plant, in the case of yams they are on different plants. They are only important when it comes to breeding improved varieties. This can best be done by crosspollinating plants with different characteristics.

Origin: The origin of the yam is in Asia, Africa, and the Carribean islands. The yellow Guinea yam originated in West Africa, together with the white Guinea yam. The three-leaved or bitter yam, also called cluster yam, likewise originates from Africa. The aerial yam or potato yam has its origins both in Africa and Asia, and the water yam, also called ten months yam, is an Asian plant.

Yam Varieties:

1. White Yam {eight-monthsyam) has white or cream flesh, stores well and produces high yields. It matures 8 months after planting.

2. Yellow Yam {twelve-months yam) has yellow flesh and matures only 12 months after planting. It does not store well nor does it produce high yields. If continually tapped it grows for as long as 3 years.

3. Water yam (ten-months yam) has white, red, or purple flesh which is very soft because of its high water content. Its storage qualities are poor.

4. Three-Leaved Yam (bitter yam) has yellow, white or pink flesh of poor quality, but it produces high yields. Its leaves are prickly with three little leaves and the stem climbs clockwise.

5. Aerial Yam {potato yam or air potato) does not develop tubers but bulbils that grow in the axils of the leaves or underground. It is of relatively poor quality and is not widely grown, but it stores well.

6. Chinese Yam (lesser yam) produces very small tubers with pale-yellow smooth skin that resemble sweet potatoes. It does not store well and matures in 12 months. Its stem is prickly and climbs clockwise. It grows best in dry, open areas.

Farming is done according to traditional methods under the system of multiple cropping. For details see the section on Traditional Farming (part I). Only on school farms are yams farmed in single cropping since they represent one of the most important school crops.

Farming: Yams need a deep, well drained soil. The best soil is sandy loam. If the soil is too heavy, the tubers may start to rot in the ground. There are varieties adapted to dry conditions (600 mm rainfall per year) and to very wet conditions (3000 mm annual rainfall). Usually the varieties grown locally are adapted to the local climate unless they have been recently introduced. The white yam needs an annual rainfall of 1000 to 1500 mm evenly distributed over 6 - 7 months. Yam grow best at temperatures around 30 °C. Frost will kill them, and if the temperature falls below 20 °C, their growth is slowed down.

Of all the root and tuber crops yams need the most labour.

For planting small tubers (seed yams) or parts of larger tubers (setts) are used. If setts are used, tops are preferable. Most varieties grow on setts weighing 250 to 500 g. Setts are planted with the cut part pointing upwards and the eyes downwards. After planting, the setts should be covered or "capped" by a layer of dry grass about 2-3 cm thick on top of the soil. This has the usual advantages of mulching. Planting holes should be 50 cm deep and 60 x 60 cm large. They should be filled with rich surface soil or manure. Yams are usually planted on mounds or ridges and only occasionally on the flat. Recommended distances are given in the table p. 122.

There are two planting times. Early planting is done in November if the soil has retained enough water to allow germination and growth during dry season. Late planting is done in February and March.

Distance Between Rows

Distance in rows

Area per Plant

Plant Population per Hectare

2.0 m

70 cm

1.40 m²

7140

1.2 m

120 cm

1.44 m²

6900

1.2 m

90 cm

1.08 m²

9260

1.8 m

60 cm

1.08 m²

9260

Staking allows the plant to develop more leaves than if no stakes are used. With more leaves the plant produces more starch and the tubers grow bigger. Stakes or "poles" should be put as near to the yam plant as possible. A strong stake, 2-2.5 m high, takes up to four yams. Young vines are guided in the direction of the stake, usually along stalks of maize or dry grass. Cluster yams are not stakes.

Weeding is done occasionally during the rains.

Hilling or earthing up becomes necessary when the upper part of the yam tuber is no longer covered with soil.

Manuring depends very much on local soil characteristics. No general indications can be given. On old farms or on sandy soil it would be good to put some compost manure in the planting holes. Chemical fertilizer should be applied when the shoots are about half a meter tall, about six to seven weeks after germination. Chemical fertilizer is applied in a ring around the plant and must not touch it directly, otherwise it might burn the yam. One or two matchboxes full for every plant would be about the right quantity.

Harvesting can be done twice. About six months after planting, the yams may be tapped. The tuber is cut so that the top remains attached to the stem. When the top is put back into the soil, it usually produces a number of smaller tubers which can be used as seed yams. The main harvest is done towards the end of the growth cycle, when the tubers are completely ripe. This is the case when the leaves begin to turn yellow.

Since damaged tubers do not store well. harvesting must be done very carefully.

Yields vary a lot. Here are a few figures:

3.5 tons/hectare: smallholders in Cameroon,
7.5 tons/hectare: African average,
9.33 tons/hectare: World average,
20 tons/hectare: good yield on well prepared and fertilized soil,
30-35 tons/hectare: yields from high yielding varieties,
70 tons/hectare: highest yield recorded.

Storage: The following rules should be applied when storing yams (for details see part IV on Tuber Preservation):

- Do not store directly on the floor. This then allows air to pass freely and prevents moisture from damaging the tubers.

- Tubers should not touch each other so as to reduce the risk of mutual infection.

- Do not expose tubers directly to light, or else they might start sprouting too early. Methods in keeping with these rules are: packing tubers in ashes and covering them with soil,

- covering them with soil and a grass mulch,

- suspending yam tubers from branches which shade them,

- tying them to a framework of poles, - putting them on rafters in a barn.

Pests and Diseases: The yam beetle attacks the tubers. No other serious pest is known. Wilting leaves or black-brown spots on leaves are caused by anthracnose. The affected leaves should be removed and destroyed as soon as possible.

Plant Improvement: Improvement by breeding and-selection is difficult with yams because the flowers rarely produce seeds which germinate. The IITA (International Institute fore Tropical Agriculture) at Ibadan has made some promising steps into the right direction, however.


Cassava

2.2.2 Cassava

Cassava farming is on the increase in West Africa. In many areas it gradually replaces yam as the staple food. Yet, it is extremely low in protein content and may lead to protein deficiencies if the daily food is not supplied with protein from other sources. The main producer countries are Brazil, countries in West Africa, Indonesia, Malagasy, Southern India, and Thailand.

The Plant: Cassava is a perennial plant growing to between 1 and 5 m tall. All its parts contain latex, a white liquid that forms an elastic cover when it dries. It has a relatively deep rooting system with feeder roots going down to a depth of 40 to 80 cm. Some of the adventitious roots start swelling and store starch. 5 to 10 such root tubers may grow on a cassava plant. The stem shows very pronounced leaf scars. The leaves are divided and look vaguely like a hand with the fingers spread out. Cassava flowers are small and light green in colour. They produce seeds. But since cassava is propagated vegetatively from stem cuttings, farmers do not pay any attention to flowers and seeds. Depending on the variety, the tubers reach a length of 15 to 100 cm. They are covered with a hard skin which has to be peeled before they can be prepared. All varieties of cassava contain a certain poison which must be washed out by soaking or destroyed by fermentation or boiling.

Origin: Cassava has its origin in South America from where it has spread to all other tropical regions. Very often cassava remains as the last crop in a cropping sequence when the soil is already too exhausted to produce anything else.

It is normally grown in multiple cropping, but towards the end of a crop sequence it is grown as a single crop after all the other crops have been harvested.

Farming: The crop grows best on sandy loams but does well on all other types of soil if they are well drained, allow the roots to penetrate deeply, and are not too stony. Even poor soils are acceptable if the roots can penetrate deep enough.

It is suited to rather dry conditions with 500 mm of annual rainfall as well as to very humid climates with a rainfall of 2 500 mm per year. It does best with an annual rainfall of 1000 to 1500 mm. Because of its well developed roots it can withstand lengthy periods of drought.

It needs an average annual temperature of 25 - 29 °C. It is therefore unsuitable for areas where temperatures fall below 10 °C or rise for long periods above 30 °C. Areas higher than 1400 m above sea level are definitely not suited for cassava growing.

Tilling is the same as for other crops.

For planting stem cuttings are used. These cuttings should be 20-30 cm long with at least three buds. They ought to be selected from the lower or middle part of the stem. Plants must be 10 months old at least before they can be used for propagation. Stems from plants suffering from a cassava disease must not be used for planting.

According to local circumstances, cassava is planted on the flat, on mounds, or on ridges. Where the soil is poorly drained, ridges or mounds are required. The cuttings may be planted upright, horizontal, or at an angle. None of these methods so far has shown a definite advantage over the others.

Distance Between Rows

Distance in Rows

Area per Plant

Plant Population per Hectare

60 cm

60 cm

0.36 m2

27 800

80 cm

80 cm

0.64 m2

15 625

120 cm

75 cm

0.90 m2

11 100

140 cm

140 cm

1.96 m2

5 100

150 cm

150 cm

2.25 m2

4 450

The table above shows planting distances with their corresponding densities (plant population). The planting distance depends again on soil fertility and the availability of water.

The best planting time is the beginning of the rainy season.

Weeding is necessary during the early growth period. During the first four months, a cassava farm should be weeded twice. Afterwards, cassava forms such a dense canopy that weed growth is negligible.

Harvesting starts 6 months, ten months or even two years after planting, depending on the cassava variety. Short-season cassava, if available, would be an interesting school farm crop. Cassava tubers do not store well when harvested. But they can be left in the ground for a prolonged period of time, usually double the time that they needed to get ripe. If they are left too long, however, they develop fibres and cannot be eaten any more. Harvesting is done by hand. Even in commercial cassava plantations, ploughs or other implements are rarely used for harvesting.

Yields depend very much on careful crop husbandry and good planting material.

5 tons/hectare: low average yields,
9 tons/hectare: world average yield,
30-40 tons/hectare: average on commercial farms and plantations,
100 tons/hectare: highest yields recorded.

Processing: Since cassava tubers start rotting immediately after harvest, they have to be stored in the soil again or must be processed. They are turned into garri or into a white powder.

Pests and Diseases: African mosaic disease and cassava bacterial blight are the most important diseases affecting cassava. Mites and nematodes cause serious damage.

Improvement: Attempts at improving cassava through breeding and selection are under way, especially in Latin America. The main aim is to make cassava varieties resistant to virus diseases.


Sweet Potatoe

2.2.3 Sweet Potatoes

The Plant: The sweet potato is a herb with trailing or twinning stems. They grow 1 - 5 m long and spread out over the ground. It is a perennial herb if left undisturbed, but it is cultivated as an annual crop, i.e. replanted after every harvest. Like cassava, it has latex in all its parts. From the nodes of the stem adventitious root systems grow out, so that one plant is fixed to the ground at several points. Some of these adventitious roots thicken and turn into tubers. The root system is shallow. These tubers have white, yellow, orange, red, purple or brown skin, the flesh may be white, yellow, orange, reddish or purple. The leaves have a number of different shapes. The flowers are in the form of a funnel, and are purplish in colour. Sweet potatoes produce fruits with seeds but these are not used for propagation by farmers.

In West Africa there are three main varieties in use, one with white skin and flesh and a rather sweet taste, one with red skin and creamy flesh, and one variety with yellow flesh. The tubers are ready 3-8 months after planting which makes them attractive as a school farm crop.

Origin: Sweet potatoes originated in the tropical areas of South America. Nowadays they are of particular importance in Asia (Japan, Taiwan, Indonesia, Korea, India). Brazil is also a main producer.

Farming: The crop needs sandy soils with a lot of organic matter. Good drainage is important since the plant does not like being waterlogged. It thrives best with an annual rainfall of 750 to 1250 mm so that it is not adapted to the very wet conditions of the forest zones. The best temperature for sweet potatoes is an average of 24 °C. Cool weather slows down plant growth, and at temperatures below 10 °C the plant is damaged. It likes sunshine from a hazy sky.

Planting is done using stem cuttings about 20-45 cm long. In some areas, the tubers are used for propagation but this is not widespread. Planting is done on ridges or mounds. The mounds or ridges should be 60 cm apart, the distance between plants in the rows/ridges is 22-30 cm. As long as there is sufficient moisture in the soil for the plants to get established, they can be planted. Sweet potatoes quickly form a very dense soil cover so that weeds are effectively suppressed and weeding is unnecessary. This means that between planting and harvesting there is no work to be done.

Harvest can-start when the leaves turn yellow and begin to drop. Another sign of maturity is that the latex of a tuber no longer turns black rapidly. When digging up the tubers, great care must be taken not to damage them since they easily get infected by fungus.

Yields:

3 tons/hectare: low yield,
8.8 tons/hectare: world average,
20 tons/hectare: satisfactory yield,
40 - 50 tons/hectare: exceptionally high yield.

Storage is difficult. In native stores (baskets under the roof, etc.) they may last up to four weeks but no longer. On the other hand, the tubers can safely be left in the ground for some time after they are ready for harvest.

Pests and Diseases: Black rot in the stems and soft rot in the tubers during storage, together with virus diseases, are the most important diseases. Various weevils, moths, and nematodes also attack the sweet potato.

Plant Improvement: Especially in the USA the plant has been greatly improved.


Colocasia (Taro)


Xanthosoma (Cocoyam)

2.2.4 Colocasia and Xanthosoma

These two crops look similar and produce similar tubers. We shall therefore treat them together. In certain countries, they are more familiar under different names: Colocasia is known as cocoyam or tarot Xanthosoma is known as new cocoyam, mamicoco (Pidgin), or macabo, in other countries as tania.

The Plants:

Colocasia is a herb, some varieties are annuals, others are perennial. It grows up to a height of 1-2 m and develops a stem tuber, the corm. The corm is cylindrical in shape and has short internodes. It may develop a few small side tubers. Some varieties have a substance in their tubers which irritates the throat so that swallowing becomes difficult. The leaves are large, their shape vaguely resembling an African hoe. The plant may produce a flower if left growing for long enough (see illustration). But since colocasia is propagated vegetatively, the flowers and seeds are of no importance.

Xanthosoma is an annual herb reaching a height of 2 m or more. Its corm is shaped like a flask and bears 10 or more side tubers called cormels. The leaves are large, growing on a strong stem, and resemble an arrowhead. The flower looks much like that of colocasia.

Origin and Areas of Cultivation: Colocasia (cocoyam) comes from Asia, Xanthosoma (mamicoco) originated in South America. Cocoyams are mainly grown in Nigeria, Ghana, Cameroon, and Ivory Coast, whereas Xanthosoma is more common in South America and the Carribean islands than in West Africa.

Farming: Colocasia prefers deep, well-drained, friable loamy soils and does not mind being waterlogged. Xanthosoma does well on a variety of soils but not on pure sandy soil or hard clay. It cannot cope with waterlogging.

Colocasia does well in areas with an annual rainfall of 1750-2500 mm. Xanthosoma is suited to much more rain but will still thrive with as little as 1000 mm of rain.

The best temperature for cocoyams lies between 21 and 27°C. Xanthosoma adapts to a wider range of temperatures (13 - 29 °C). Both plants are forest plants rather than savannah plants. They do well under shade.

For planting, corms or cormels are used. Pieces of corms or cormels are planted at a depth of about 10 cm. Often, planting is done on mounds or ridges. Planting distances are

for Colocasia

30 x 30 cm (very wet farms)
60 x 60 cm average spacing
90 x 90 cm (areas with very high rainfall)

for Xanthosoma

60 x 60 cm
90 x 90 cm (West African habit)
180x 180cm

Planting time is at the beginning of the rainy season. Both crops are usually grown under the system of multiple cropping. Since they do not mind shade, they can do well on tree crop farms, especially with coffee and young cocoa.

Weeding is necessary only in the early stages of growth.

Colocasia harvesting starts six to 18 months after planting, depending on the variety grown. Xanthosoma is ready 12 months after planting at the latest, and early varieties are ready after six months. Xanthosoma would seem to be better suited for school farm work than cocoyams. Both crops are ready when the leaves start turning yellow. They are then dug up and stored.

Yields:

Colocasia

average

5 - 20 tons/hectare

maximum

75 tons/hectare

Xanthosoma

average

5 - 20 tons/hectare

maximum

70 tons/hectare

Pests and Diseases: Colocasia suffers from leaf blight, various leaf spot diseases, soft rot and tuber rot. A number of insects attack the crop, mostly the leaves. Xanthosoma suffers much less from pests and diseases.

(introduction...)


Arabica Cofee

3.1 Coffee

Coffee, like tea, and to some extent cocoa, is grown for the stimulant contained in parts of the plant. Stimulants are substances which activate the human body. For example, coffee relieves fatigue. The stimulant in coffee is concentrated most in the coffee seed, the so-called coffee bean.

The Plant: Coffee is a perennial plant, a shrub growing up to a height of 3 m if left alone. Two main varieties are known, both of which are grown in Africa. One is arabica or highland coffee, the other is robusta coffee, adapted to lowland conditions. The two varieties differ in many respects which will become clear as we discuss them. The plant is a shallow feeder with the mass of its roots concentrated near the surface of the soil. Arabica coffee develops a deeper root system than robusta and therefore resists drought better.

On the coffee stem there are two types of buds. One type of buds grows horizontal branches, the other grows new stems if the initial stem is removed or bent down. This feature is used in coffee pruning produce trees with several stems. The leaves are single, and dark green in colour. The leaves of arabica coffee are smaller than those of robusta coffee. Coffee flowers are white and have an intense, pleasantly sweet smell. They grow in groups at the leaf axils all along the branches. The coffee fruit is a berry with a dark red coat, juicy, red pulp, and a seed clearly divided into two halves.

The time between flowering and harvesting is 9 months for arabica coffee, 10-11 months for robusta coffee. Flowering always starts after the first rains in the case of arabica coffee whereas there is no exact time for flowering with robusta coffee. Arabica coffee has a better taste than robusta coffee and less caffein, the stimulant for which coffee is grown. Arabica coffee produces lower yields per hectare than robusta coffee.

Origin: Coffee is an African plant. Early reports name Ethiopia as the home of coffee. Initially, coffee leaves were used like tea leaves to prepare a drink. Coffee was widely used in the Muslim world. When the Turkish army broke off the siege of Vienna (Austria), they left a load of coffee beans in their camp. Coffee drinking in Europe started from that time, and the first coffee houses were opened.

Production: Arabica coffee is still by far the most important type; 74% of world coffee production is arabica, 25% is robusta, the remainder being shared between three other minor coffee varieties. Robusta coffee is on the increase, however, due to the fact that it can easily be processed into instant coffee without too much loss of taste. The table p. 133 shows some production figures for 1962 and 1972 (in 1000 tons). Kenya and Tanzania, too, are important coffee producers.

Farming Coffee needs deep, well drained and well aerated soil. It does not like acid soils. Because of its high nutrient require meets it needs manure or chemical fertilizer.

Arabica-coffee

Country

1962

1972

Brazil

1720

1500

Columbia

468

680

Mexico

140

222

Ethiopia

132

216

El Salvador

97

150

Guatemala

108

140

Robusta-coffee

Country

1962

1972

Ivory Coast

195

270

Angola

185

215

Uganda

120

200

Indonesia

111

185

Source: adapted from Rehm/Espig, 1976, table 35 p. 241

Arabica coffee does best at an annual rainfall of between 1500 mm and 2000 mm and an annual dry season of 2-3 months. At the beginning of the first rains the trees start flowering immediately. Robusta coffee needs an annual rainfall of between 2000 and 3000 mm. It does not need a definite dry season but can withstand one to two months of drought.

Coffee needs a relatively high average temperature, arabica coffee between 17 and 23 C, robusta coffee between 18 and 27°C. In order to do well coffee must grow under shade, at least during the early stages of growth. Where shade cannot be made available, thick mulch serves the purpose of keeping soil temperatures low. Once the trees are well established and have started yielding, shading is no longer required. They yield best under full sunlight.

Farm preparation should be done at least six months before planting, i.e. roughly at the same time that the nursery is made. Planting distances on the coffee farm vary with local conditions, as can be seen from the table below. The planting holes should be filled with rich, manured top-soil.

Coffee is propagated by seedlings that are raised in a nursery Nurseries are usually made by using polythene bags. These are filled with rich soil in which a coffee berry is planted. For healthy seedlings berries from strong, well-yielding trees should be collected. These must be pulped, dried and packed in wood-ash if they are not to be used immediately for planting.

Seedlings are ready for transplanting when they have six pairs of leaves. Hybrid varieties such as "arabusta" are propagated from stem cuttings. The Agricultural Department grows coffee seedlings of high quality and distributes them to interested farmers. In order to do well, the seedlings need shade. It is therefore advisable to leave some trees on the future coffee farm for shade. If this is not possible as in most grassland areas, bananas, plantains or tephrosia should be planted in order to provide sufficient shade. A 20 cm layer of mulch can replace shading if necessary. The best time for transplanting from the nursery to the farm is the start of the rainy season.

Planting Distance

Plant Population per Hectare

Remarks

2 m x 1.5 m

3330

arabica coffee, very wet conditions

2 m x 2 m

2500

arabica coffee, normal spacing in Cameroon

2.7 m x 2.7 m

1370

normal spacing in Kenya

3 m x 3 m

1110

robusta coffee, standard spacing in Cameroon

4 m x 4 m

830

spacing under very dry conditions

Intercropping in coffee is possible provided that only very light tilling is done. Since the mass of the roots are quite near the surface, they are easily damaged during tillage.

It is recommended that the young trees be pruned in such a way that they grow several instead of only one stem. Since each stem grows its own branches, the yield per tree will be higher than with only one stem. By cutting the main stem, the farmer forces the tree to replace it, This it does by growing several stems at the same time.

Weeding should be done carefully on the young coffee farm. Shading and/or mulching will keep weed growth in check, however. Once good canopy has been formed it will suppress most of the weeds.

Pruning is done each year in order to cut off unwanted branches which would use up plant food that would otherwise go into the growth of coffee berries.

The use of artificial fertilizer of course also varies with soil conditions. Quantities to be applied are:

Nitrogen: 150 - 200kg/hectare
Phosphorus: 25-40 kg/hectare
Potassium: 80-160 kg/hectare

Coffee yields start going down after 7 - 10 years of harvesting. In this case, it is not necessary to replant the whole farm. It is possible to rejuvenate the trees (i.e. to make them young again): the main stem is cut off as low as possible just above the lowest branches. New shoots quickly grow, bringing back the full yield of earlier years.

Harvesting extends over a long period because only fully matured, red berries should be picked. Green berries are not suitable for high quality coffee. A well trained worker can pick between 30 and 60 kg of berries per day.

Yields:

514 kg of dry beans/hectare: world average,
1500-2500 kg of dry beans/hectare: well tended arabica coffee,
2300 - 4000 kg of dry beans/hectare: well tended robusta coffee.

Farmers have to process their coffee before they sell it. They either dry the whole coffee berry and sell it afterwards, or they pulp it, i.e. remove the juicy flesh from the coffee beans. The pulped beans are left fermenting and are dried afterwards. Now they are called parchment coffee and are ready for sale. The buyers hull and polish them so that they can be sold for export.

Pests and Diseases: Coffee is attacked by a number of fungus diseases. The really dangerous ones are coffee rust and coffee berry -disease. These can be fought by spraying. Here, the agricultural extension agents and the coffee demonstrators of the cooperative unions will be of help. There are a few insect pests like the coffee stem borer and the coffee berry borer which can be checked by insecticides.


Cocoa

3.2 Cocoa

Cacao is another tree crop yielding a fruit which, in Africa, is mainly farmed for export. The growers themselves do not use it as food or drink. Several varieties are known. In English, the tree and its fruit are spelt "cacao" whereas the products derived from the fruit (e.g. cocoa powder, cocoa butter, and the cocoa drink) are spelt "cocoa". This rule is not universally respected, however, and some texts talk of the "cocoa tree" and the "cocoa pods"

The Plant: Cacao is a relatively short tree belonging to the vegetation of the rainforest. If left alone it would reach a height of 1215 m. In cacao plantations it is kept much lower in order to make harvesting easier. The tree grows 3 - 5 main branches. Its tap root reaches about 2 m into the soil. The feeder roots, however, remain in the upper levels of the soil, preventing any deep hoeing for intercropping.

The flowers grow from "cushions", swellings on the stem and the main branches at places where leaves had formerly grown. The flowers are very small and whitish-pink in colour. In the right climate they continue growing out of the same cushion for years provided the cushions are not damaged at harvesting. Flowering is at its height from April to July. Accordingly, peak harvesting takes place from October to December. The fruits are large pods each containing 30-40 beans. Depending on the variety, ripe pods change from green or deep red to yellow or reddish yellow. The pods are usually ripe five to seven months after flowering. A tree bears between 20 and 60 pods per season. It starts yielding 3-7 years after planting, and yields go down after about 25 years. Experience has shown that in Cameroon, a cacao tree older than 35 years has no economic value any longer. Elsewhere, the economic life of a cacao tree may be much longer.

In any event, establishing a cacao plantation is a long term investment. The initial labour will yield economic returns over most of the lifetime of an adult person.

Origin: The home of cacao is South America from where it was brought to Africa and Asia. Cacao trees grow wild in the Amazonas basin. They were cultivated by the Mayas where cacao beans were used both as money and to prepare a drink. It is a relatively new plant in Africa. The Portuguese introduced . to the island of Sao Tome in 1822, the English brought it to Ghana, and the Germans to Cameroon.

Production: At present, cacao is mainly produced in Africa. In 1972, the situation was as follows:

Country or region

cacao production (in million tons)

Ghana

0.42

Nigeria

0.24

Ivory Coast

0.18

Cameroon

0.08

other African countries

0.11

Total West Africa

1.03

Brazil

0.20

other Latin American countries

0.18

Total Latin America

0.33

Asia and Oceania

0.05

World Production

1.48

Cacao farming has expanded very fast in Africa during this century, as can be seen from the following figures:

Year

Cacao Production in Africa (in tons)

Share of World Production

1900/1

19 700

17.0%

1921/22

232 800

53.9%

1938/39

544 300

68.1%

1971/72

1 129 100

73.7%

adapted from: Assoumou, J., 1977, p. 81

Thus, nearly three quarters of the world cacao production come from Africa. During the same period, world consumption of cacao has grown tremendously, showing how popular such items as chocolate, cocoa powder etc. have become:

Year

World Consumption of cocoa (in tons)

1910

196 000

1949

704 000

1960

922 000

1965

1 333 000

1970

1 348 889

adapted from: Assoumou, J., 1977, p. 61

Cocoa consumption in 1970 was nearly seven times that of 1910.

Cacao assumes an important place in the economy of the main producer countries. In 1972, it accounted for 60 per cent of all the exports of Ghana, for 30 per cent of all the exports of Togo, and for 22 per cent of Cameroonian exports.

Farming: Cacao needs a deep, well-drained soil which should retain water reasonably well. If the soil contains enough organic matter it can even be slightly acidic. The tree does not do well immediately after burning, food crops should be farmed for one season before transplanting the cacao seedlings. Cacao does not place heavy demands on soil fertility.

Its water requirements are high, doing best where the rain is distributed evenly through out the year and totals 1500 - 2000 mm per year. It does very well under shade. As long as it has not formed a dense canopy it needs heavy shading. However, average temperatures ought to be high - about 32°C.

Farm preparation: The future cacao plantation is prepared by digging holes about 30 cm deep and 20 cm square. Before planting the seedlings, these holes should be filled with rich top-soil or manure. Planting distances are shown below.

Nursery work: Young cacao trees are usually grown from seeds. As with coffee, a nursery is made with one seedling to each bag. Seedlings should grow 4 - 8 months before they are ready for transplanting, the nursery should be started so early that with the onset of the heavy rains the seedlings can be transplanted. They must always be grown under shade. The agricultural department sets up nurseries where seedlings are grown for distribution to farmers.

Weeding is necessary as long as the canopy is not closed. As long as the trees have not started bearing fruit, food crops can be grown between the young trees. Later on, the dense canopy prevents any but the most shadeloving crops (colocasia, xanthosoma) from doing well.

Mulching is important for young cacao seedlings and trees, especially if shade cannot be provided in sufficient quantity. It is still recommended later on in order to maintain a high level of organic matter in the soil.

Planting Distance

Plant Population per Hectare

Remarks

1.5 m x 2 m

3300

observed in Haiti

2.5 m X 2.5 m

1500

standard distances in Cameroon

3.0 m x 3.0 m

1110

recommended by specialists

4.0 m x 4.0 m

625

recommended by specialists

5.0 m x 5.0 m

400

observed in Angola

Pruning is said to be the most important activity in cacao farming. Pruning means cutting away dead branches, twiggy growth from the main branches, upward growing shoots, and branches too close to the soil.

Chemical fertilizers are necessary in small quantities only. Many of the nutrients used by the fruits are returned to the soil if the shells of the cacao pods are left in the plantation. If fertilizer is applied, the recommended rate is 100 kg of nitrogen, 20 kg of phosphorus, and 70 kg of potassium per hectare and year. This quantity is not given once but in three applications: one third at the time of most intense leaf growth, one third at the main flowering period, and one third when fruit is at its height.

Harvesting requires a lot of skill. Neither unripe nor overripe pods should be picked. In order not to damage the cushions, a sharp knife must be used. In this way, the pods are cut rather than picked. When a sufficient number of pods have been harvested, they are split open on the farm. The cacao beans, covered with their white pulp, are then carried away for further processing.

About 20 pods yield one kg of dry beans. Yields are far from what they could be. Here are a few figures on cacao yields (kg/hectare):

1000-1500: good yields,
250-350: average smallholder plantation in Cameroon,
600-900: well kept smallholder plantations in Ghana, Togo, and Nigeria,
3000: yield from high yielding varieties under best conditions.

Processing The beans are fermented in their pulp. This takes about a week, but the beans have to be stirred and well turned in the fermenting boxes every two days. The beans produce a lot of heat while fermenting. After fermentation, the beans have to be deed. In the humid rainforest areas, the heat of the sun is not sufficient to dry them properly. Many cacao farmers use drying ovens where they keep a fire burning until all the beans have been properly dried. The extension officers have detailed instructions about how to ferment and dry cacao. The quality of the cacao, its grade and thus its market price depends as much on proper processing as on good farming practices.

Pests and Diseases: The worst cacao diseases is Black Pod Disease, a fungus disease which turns the pods black and spoils the beans. Before an effective chemical was found, Black Pod Disease could ruin a whole year's crop: In Nigeria, up to 80 per cent of the crop were lost to the disease. In Cameroon, losses of up to 50 per cent have been reported.

Another severe disease is Swollen Shoot Disease. Since no remedy has been found to fight it, affected trees have to be felled and burnt. Thus, between 1946 and 1967, 130 million trees had to be felled in Ghana alone.

The most important insect pests are the capsids. They attack the pods and the young shoots by sucking sap from them. Capsids do not destroy the affected pods but they weaken the whole tree so that it does not yield as it normally would.

4.1 Tables of yields

Coffee Robusta

Yield in kg/hectare

Remarks

167-273

Fako Division, South-West Province, Cameroon

237

sample of farmers, South West-Province 1975

780-1120

Nigeria, fresh berries, average for smallholders

600

experimental plot, Kumba, dried berries

100-500

average range for Africa, dried berries

1000

average in Latin America, dried berries

2300-4000

very well kept coffee farms, dried berries

Coffee Arabica

Yield in kg/hectare

Remarks

210-320

North-West Province, Cameroon, dried beans

190-350

Santa Coffee Estate, Cameroon, 1959-1966

334

sample of farmers, North-West Province, Cameroon, in 1973/74

440

Nso and Ndu, Cameroon, random sample of farmers in 1971

1500

trial plot at Wum, Cameroon, fresh berries

1500-2500

very well kept farms, dried berries

Cacao

Yield in kg/hectare

Remarks

130-180

Fako-Division, Cameroon, smallholders in 1973/74

205

sample of farmers in Soutb-West Province, Cameroon, 1975

270-550

German plantations at Victoria at the beginning of the century

315

world average in 1972

250-350

average smallholder plantation, Cameroon

600-900

well kept smallholder plantations, Ghana, Togo, Nigeria

1000-1500

good yields

2250-3350

maximum yields under the best conditions

Oil Palms

Yield in kg/hectare

Remarks

1100-2250

fresh fruit bunches, native farming, West Africa

2000

smallholders' harvest from wild palms, West Africa

6700

average yield in West Africa, all farmers

10500

smallholders, Ivory Coast

5700

CDC-estates 1972/73

14800

Nigeria, Plantation estate 1974

26100

Indonesia, Plantation estate

Yams

Yield in kg/hectare

Remarks

3500

smallholders in Cameroon

7500

average for Africa

9330

world average

12550

experimental yields, R.T.C. Kumba, Cameroon

16250 - 20960

experimental yields at TTC Nchang, Cameroon

30000-35000

high yielding varieties

70000

maximum yields

Cassava

Yield in kg/hectare

Remarks

4000

smallholders in Cameroon

4500

experimental yields in North-West Province, Cameroon

5000

low average yields

12000-24700

range of yields in West-Africa

30000-40000

average in commercial cassava farming (large areas)

100000

highest yields

Colocasia

Yield in kg/hectare

Remarks

2800

smallholders in Cameroon

5000-20000

range of average yields

75000

maximum yields

Sweet Potatoes

Yield in kg/hectare

Remarks

3000

smallholders in Cameroon

7400 - 14800

range of yields in West Africa

8800

world average

20000

satisfactory yields

40000-50000

exceptionally high yields

Plantains and Bananas

Yield in kg/hectare

Remarks

21700-37000

average in West Africa

Beans

Yield in kg/hectare

Remarks

62.4

trial plot at Wum North-West Province, Cameroon

500-1100

range of good yields, common beans, dry seeds

25 00

maximum yield

Groundnuts

Yield in kg/hectare

Remarks

330 - 560

smallholders, West Africa

600-800

average yields

670-1100

experimental yields, West Africa

1520-3000

experimental yields, Wum, Cameroon

Cowpeas

Yield in kg/hectare

Remarks

300-400

average yields

2800

maximum yield

Rice

Yield in kg/hectare

Remarks

760

smallholders, North-West Province, Cameroon, upland rice

900-1700

upland rice, normal range of yields

3000

maximum yield for upland rice

1000-1500

poor yields of irrigated rice

1760

average in North West Province, Cameroon, irrigated rice

2250-4500

irrigated rice, West Africa, good conditions

2300

irrigated rice, world average

4220

experimental yield, R.T.C. Kumba, Cameroon, 1977

6000

medium yields from high yielding varieties

10000

maximum yields

4.2 Farm activities associated with different crops

Note: The table shows which activities occur with a given crop. Clearly, words used with several or all crops are the most common ones and should be well taught and well learnt in all ways possible. Words occuring with only one or two crops are specialized vocabulary. Reading the table for each crop gives an idea about the word drill needed for teaching about that particular crop. It also shows the difficulty of successfully farming a crop: the more detailed the vocabulary, the more different skills are needed in farming.

The text on any particular crop will use all the words mentioned in the table for that crop. They will either be explained explicity or become clear from the context.


Figure

1.1 Extent of the problem

It is especially difficult to store grain in tropical climates which are always wet and warm with many grain pests living all through the year. The major enemies or pests of stored grain are:

1. Mould and Fungus (these are very tiny plants which grow on grain surface and cause spoilage; they thrive in warm, wet grain),

2. Insects,
3. Rats,
4. Birds.

All four of these major pests thrive during the rainy season and dry season. However, one ought to distinguish different climate zones: the rain forest and the drier highlands. Each zone has different problems with grain storage.

In the highlands, often grain (maize, beans, and rice) is the principal crop and food of the people. Insects and rats are the- primary enemies of stored grain. Between 10% and 15% of the grain grown in the highlands is lost during the storage period.

In the rain forest regions people do not grow large amounts of grain. It is very difficult to dry and store maize, beans, or rice there. Moulds, fungus, insects and rats are the main problems with grain storage. Studies have shown that between 15% and 20% of the grain stored is destroyed by these pests.

1.2 Types of grain storage losses

Before we look at how one can stop the destruction of grain in storage it is important to know which kinds of loss should be stopped.

a) Loss in Weight

Rats, birds, and insects cause this type of loss. The grain has been eaten so that the original weight of the grain has been reduced. The food and nutritional value has been reduced because of the loss of gross weight. This kind of loss is easy to locate.

b) Loss in Quality

Stored grain can also suffer from a loss in quality or food value. Rats and insects can spoil the grain with their urine and droppings. Mould and fungus also spoil the grain with tinier own wastes. You can become sick if you eat grain which has been made dirty by the droppings and waste from rats, insects, and moulds.

c) Seed Loss

Insects, rats, and birds can eat and damage the kernel in such a way that the seed cannot germinate. When they attack the seed embryo (see the Figure p. 153) the seed can die and it will not grow into a new plant.

It is important to realize that grain must be protected against loss of weight, quality, and seed.

1.3 Costs and benefits of grain storage

a) Costs of Grain Loss

In order to understand the importance of using correct grain storage methods it would be wise to see how much grain losses really cost. The following example should be helpful.

Mr. Ngwa Joseph is a farmer in MBali. His one hectare farm produces 1000 kg of maize, this fills 10 produce bags every year. However, just as other MBali farmers, Mr. Ngwa suffers from insects and rats which destroy about 10% of his maize crop each year.

This means that Mr. Ngwa will lose 10 kg of maize from each 100 kg bag of maize he tries to store. Therefore, of his 10 bags stored he will lose 10% or one bag each year,

On MBali market day, Mr. Ngwa can sell his grain for about 5000 francs a bag. When Mr. Ngwa lost his one bag of maize (10% of 10 bags) he actually lost 5000 francs. Furthermore, all the time, work, and materials he used in growing this "lost" 100 kg of maize has now been wasted.

If Mr. Ngwa continues to lose 10% of his grain each year, after five years he will have lost 5 x 5000 frs. = 25000 frs. worth of grain.

b) Benefits of Correct Grain Storage

Using good grain storage techniques helps the farmer and the community as a whole.

The farmer benefits because:

- he has more grain to eat or sell as he chooses,
- his grain is not spoiled, it is safer to eat,
- good clean grain can get a better price in the market,
- he can grow more grain without fear of losing it to insects, rats, and birds.

The community benefits because:

- there is more grain to buy,
- the grain is better, cleaner, and safer,
- the price increases during the time of scarcity would be reduced.

Using good grain storage methods helps everyone.

(introduction...)

In order to understand why stored grain should be treated in certain ways it is important to know what grain is and how it is constructed.

2.1 Grain kernel structure

All seeds or kernels of grain are made up of three basic parts; the seed coat, the endosperm, and the embryo.

a) The Seed Coat

This is the protective "skin" or shell which surrounds the endosperm and embryo. It is a waxy-hard covering. It can protect the kernel only if it is dry, unbroken, and strong. If the seed coat is dry and sound weevils, mould, and fungus find it very difficult to attack the grain.

b) The Endosperm

This is the food that the seed uses while it is in storage and when it germinates into a sprout. The endosperm is soft and flourlike, it makes up over 75% of the kernel. If the grain is well dried the endosperm will be able to resist mould and fungus attacks.

c) The Embryo

The embryo is the part of the seed which germinates and forms the new plant. The embryo is located at the bottom or end tip of the seed. Insects and rats like this part of the seed very much because it contains most of the proteins and food value. If the embryo is eaten the seed will not germinate.


A Normal Rice Kernel

2.2 Biology of grain in storage

Grain is a living thing. Just as people, animals, and birds eat and breathe to stay alive, grain in storage also requires the same things to remain alive and healthy.

All living grain respirates This means that grain "breathes" or takes in air (oxygen) and consumes (eats) part of its stored food from the endosperm. The grain kernel then gives off (breathes out) heat and used air (carbon dioxide). This process is called respiration. All through the storage period living grain respirates.

Remember that living grain stores better than grain which is not alive. Grain which is not alive spoils easier than living grain.

2.3 Moisture, temperature, and respiration

The wetness of the grain and the temperature of the grain are the two most important conditions in grain storage. Grain stores best when it is cool and dry. When grain is cool and dry it respirates very slowly: This means that it breathes slowly and only gives out small amounts of heat and used air (carbon dioxide).

Grain which is wet and/or warm breathes or respirates very fast. It breathes out much heat and used air.

Insects and mould like grain which is warm and not dry. The grain can spoil very easily when it is wet and hot.

2.4 Conclusions

Grain kernels are very complex living things. Grain should always be kept cool and dry. This makes the protective seed coat hard and strong. It is difficult for insects arid mould to attack this kind of grain. Also, cool, dry grain respirates very slowly. This is good for storage.

If grain is wet and hot it will breathe very fast. This actually makes the grain even hotter and will cause even faster respiration.

It is easier for insects and spoilage to ruin grain which is wet and warm. The seed can even begin to germinate in the store. Remember that correct grain storage begins with living, healthy grain which is kept cool and dry.

3.1 Harvesting: when is grain ready

Harvesting the grain at the correct time and in the correct manner will make grain storage easier.
It is necessary to harvest only ripe, mature grains. If a farmer harvests too early there will be too many unripe, wet grains which can spoil easily. However, it is also dangerous to leave the crop in the field too long where rats, insects, and birds can damage it while it dries. Knowing when to harvest is important.

a) Maize

Maize becomes mature and acceptable for harvest when the kernels reach the "hard dough" stage. At this time the kernels are full, hard and have reached their natural colour. You can still mark or scratch the kernel with your fingernail if you press hard. Another sign of maturity is when the silky hairs coming out of the top of the maize cob turn to brown. Also, a black coloured line forms at its point of attachment on the cob.

If maturity comes during the period of heavy rains further drying in the field is very difficult. It is best to harvest the maize and take it out of the rain to dry. If birds and insects are a problem in your area it is best to get the maize out of the field and into a drying place where field pests are not a problem. However, if there is no problem with maize maturing during the rainy season and field pests are not a problem, then leaving the maize in the field to dry is acceptable.

It is best to harvest maize when the weather is as dry and hot as possible. Maize harvested during a rain can get wet and is open to mould and fungus attack which can easily spoil the grain.

b) Rice

Determining when to harvest swamp rice is very difficult. A large number of farmers wait too long to harvest their rice. They often wait until the stem and leaves of the rice plant are yellow and brown. Many times this is too late. Rice which is harvested late can be lost during the harvest due to overdry grains falling off the plant. Birds and rats also attack the dry rice in the field. The following signs show when rice is ready for harvest:

- The head or panicles of grain are yellow; the stem and leaves may still be green, but the head is yellow.

- Remove the hull from a few grains at the top of the head of grain. The rice grain should be clear and hard. (Press them with your fingernail.)

- Select a few kernels of paddy rice from the center of the head or panicle. They should give a dry snap or crack when you bite them.

Finally, there should be no water or morning dew on the rice when you harvest. Just as with maize there should be not rain when you are harvesting.

c) Groundnuts

The groundout is usually ready for harvest when the leaves begin to wilt and turn yellow. The seeds should be full with the skins showing the normal variety colour. The inside of the shell should be dark brown and hard. Groundnuts which have been harvested too early tend to shrink and shrivel.

It is important to dry the groundnuts immediately after harvest. The unshelled kernels should be placed outside - but not in direct sunlight. This will cure them after a few days. Once again do not harvest during a rain.

3.2 Grain cleaning

Farmers should know that clean grain stores better than grain which is dirty. During the harvest grain becomes mixed with small amounts of straw, dirt, sand, and weed seeds. These materials are harmful during drying and storage.

Dirty grain has less market value'. Also, the dirt hides insects, moulds, and other diseases which can attack and damage the grain. The dirt makes the grain stay hotter, it stops the grain from breathing normally.

Farmers should clean their grain well before storing it. If grain is moved to a new store it is wise to clean it again.

3.3 Selection of grain for storage

It is important for farmers to select only healthy, sound grains for storage. There is an African proverb which says that, "one bad cocoyam spoils all the achu." This is true in stored. produce as well. If good grain is mixed with grain which is too wet, spoiled, or filled with insects then the good grains will soon be attacked and damaged by the bad grains. Farmers should select clean, dry, unspoiled, insect free grain for storage.

3.4 Preparing and cleaning your grain store

All grain containers and storage places should be well cleaned at the end and beginning of each storage season. A dirty, unrepaired grain store is ideal for insects, rats, and other pests to live and have families. The old, broken pieces of grain and empty shells can supply insects and rats with food until the new grain comes into the store after the latest harvest. Therefore:

- Sweep up all dust, old grain and empty shells. These should be burnt to kill all insects and insect eggs which could be hiding inside.

- Fill and seal all cracks and holes in the floor, walls, and roof. Big rats can enter through holes the size of a small coin 3 cm in diameter. The small house rat or mouse can squeeze through a hole the size of a coin which is less than 2 cm in diameter.

- Insects can hide and live in the tiny cracks in floors and walls. A tiny crack the width of a coin can house at least six grain beetles which you can multiply to 76000000 within six months. If you can afford it, paint your grain store walls; the paint will fill the very tiny cracks which insects like.

- Clean the area around your grain store. The ground should be swept clean of all empty tins, sticks, or other objects which could hide grain pests. The grass should be kept cut around the building.

- All empty grain containers must be thoroughly cleaned. Old jute bags should be shook clean. Nevertheless, insects and insect eggs can still be holding on in between the jute fibers Place the bag in the hot sun for four hours the sun's heat will drive off all adult insects and most eggs cannot live at that temperature.

If rats and insects always bother your grain store you might have to use an insecticide or rat poison to control the pests. See Chapters 6 and 7 for pest control measures, also the Agriculture field staff in your area.

Farmers should know that an ounce of prevention is worth a pound of cure. Correct preparations make grain storage much more successful.

4.1 Why grains must be dried

As explained in Chapter 2 all grain contains moisture. The problem is keeping the amount of water in the grain at a very low level. If the grain is wet then the seed coat is not strong enough to keep out insects and moulds which cause spoilage. Also, if the grain is wet it will respirate much faster. This will increase the temperature of the grain. Insects and moulds like warm grain. The grain kernels could even germinate insede the storage place once they are warm and wet enough.

It is well known by experienced farmers that dry grain stores much better and safer than grain which is wet. Unfortunately, in some regions grain (maize and beans) becomes ripe and ready for harvest during the heavy rains. In the rain forest zones grain is harvested all through the year. Therefore the grain drying problem is an important one.

4.2 What Makes grain dry

The first point to remember about grain drying is that it is the air or the wind which actually removes moisture from the grain and dries it.

A kernel of grain can become dry or wet depending on the dryness or wetness of the air which surrounds it

Grain will dry if the air around it is drier than the grain itself. The moisture will move out of the grain and into the air. However, if the amount of moisture in the air is more than the moisture in the grain then the grain can become wetter as it takes up (absorbs) the water from the wet air. (This is why drying grain during the rainy season is so difficult.)

The quickest drying takes place when grain is exposed to warm, dry, moving air. The air must be dry so that it can draw the moisture out of the grain. The air should be warm so that the drying can take place faster. Finally' the air should be moving so that it can carry the moisture away from the drying grain.

If a farmer can select a grain drying place or method which follows the conditions set out in the above section, then he or she can easily dry his or her grain even during the rainy season. The problem is finding such a correct drying method which is not too expensive for the farmer's income and yet of the correct size and type so that it fills his or her needs. A few inexpensive grain drying models are presented in this chapter, section 4.5.


How Grain Dries

4.3 How much drying is enough: Safe drying limits

Sometimes grain can be dried too much or at too hot a temperature. This can cause the grain to lose value because the heat has spoiled it. For example the seed coats of rice and maize can shatter or crack if they are dried at very hot temperatures. Once the seed coat is broken like this insects and moulds can easily enter and damage the grain. Furthermore, when over-dried rice is hulled many more grains get broken and powdered; more rice is lost during the hulling. Therefore farmers should know that the amount of drying and the temperature used to dry the grain should depend upon the final use of the grain. That is to say, grain which will be used for seed cannot be dried as hot as the grain which will be used for poultry feed. The following measures are safe drying temperature limits.

Animal Feed

75ºC

Grain for human consumption

60ºC

Grain to be milled for flour

60ºC

Rice for human consumption

45ºC

Seed grain and grain for brewing beer

43ºC

Beans for human consumption

35ºC

If you dry grain which will be used for seed or for brewing at very hot temperatures the grain will die. Once the grain has died it cannot be used for seed or for making beer. Therefore, do not dry seed grains too close to the fire; also do not let seed grains lie in the direct sun for long periods-of time sunlight temperature can reach 50 °C Nevertheless, most traditional drying methods are safe for all types of grain use.

4.4 How to test the grain for dryness

It is also important to know when the drying of the grain is finished. There are many electric machines which can. determine the amount of moisture in grain. However, they are very expensive. Most farmers cannot afford them. The best way for a farmer to find nut if the grain is dry enough is by using simple, local tests: Many of these methods are well known:

a) Bite the kernel between your teeth - the kernel should be hard to crack - it should give a loud snap when it breaks (this of course only works with maize and rice - oil seeds like groundnuts cannot be tested like cereal grains).

b) Thrust your hand and arm into an open sack of grain; if your hand and arm can enter into the grain up to the elbow, then the grain is dry.

c) to test maize for dryness take a small glass jar (a "Globus" or "shivers" jam jar) and put one tablespoon of dry salt (the salt must be loose and dry) into the jar. Then add about three tablespoons of the maize you wish to test for dryness. Cover the jar and shake briefly. Put the jar in the shade. After one minute if the salt does not stick or gum together the maize is dry enough for bag storage. However, if the salt sticks together and gums with the maize then the grain needs to be dried further.

Most experienced farmers know how to tell if their grain is dry enough for storage.

4.5 Drying methods

Now it is time to look at some actual drying techniques.

a) Natural Drying Methods

Field Drying: Many farmers leave their crop in the field to dry. This is especially true for beans and sometimes for maize. Rice should never dry in the field. Using this method the farmer relies on the natural weather conditions (hopefully they are dry enough) to dry his or her crop.

If one is field drying maize, the stem should be broken, once the maize is ripe, so that the heads of the maize cobs can be bent towards the ground. Any rain that falls will find it difficult to enter the cob of maize if it is turned upside down.

Advantages:

- Air passes freely through the field.
- Labour involved is very small.

Disadvantages:

- Squirrels, rats, birds, and insects can attack the grain with ease.
- Grain can fall on the ground and spoil.
- Often the rainy season makes this type of drying too dangerous.

Sun Drying: The oldest and perhaps best known drying method is sunning the grain.

The harvested grain is spread thinly and evenly directly under the sun on mats, bamboo racks, cement slabs, or tarpaulins. The grain should not be placed directly on the ground.

The grain should be spread on the ground in a layer about 5 to 7.5 cm thick (the length of your index finger). The grain should be stirred often so that wet grains are brought to the top of the layer to dry and that warm, drier grains are cooled down as they mix with the cooler grain from the bottom. The grain should always be closely watched so that when rain storms come it can be gathered in quickly.

This method dries grain quickly and cheaply. All the conditions in Section 4.2 are met; the sun makes the air warm and dry. When you stir the grain often the breeze can pass in between the grain kernels to carry the moisture away. Another advantage is that the heat from the sun also bothers the insects; they will not stay in grain which is being sunned.

This method does have some disadvantages:

- The grain must be brought under shelter every night to avoid the morning dew.
- Birds, rats, and goats can enter the drying area and eat the grain.
- Drying during the rainy season is still difficult.


An Improved Solar Drier

There is a way to improve upon the traditional sun drying method. A simple drying box can be constructed and covered with plastic sheeting.

- Construct from planks or plywood a shallow box of the following dimensions: 2 m wide by 3 m long and 20 cm high.

- Drill or cut ventilation holes in the walls of the box. The holes should be about 2 cm in diameter. Very small holes (smaller than the grain to be dried) should be made in the bottom of the box. Remember that moving air is needed to carry away moisture - the ventilation holes allow the air to pass.

- The floor of the box must be raised off the ground. Therefore, place the box on short legs about 15 to 20 cm high.

Now a drying roof must be constructed.

- Buy a 3 by 5 m sheet of plastic in the market.

- Construct a simple wooden frame with dimensions of 2 m by 3 m from thin sticks which will fit on top of the 2 m by 3 m drying box.

- Stretch the plastic sheeting over the roof frame and attach it.

Now the box can be placed in the sun. Then the box is filled with maize 5 to 7.5 cm deep. The plastic roof is then placed over the box and tied to it so that the wind will not blow it away. The inside of the box will become very hot air can pass over and through the grain by the ventilating holes in the side walls and floor. The grain will dry very fast. Even if rain falls the roof will keep the grain out of the rain. Remember to stir the maize from time to time. Remove the grain each evening so the grain will not sweat in the box.

This 2 m by 3 m box with 6 to 7.5 cm of grain spread on the floor will hold between 225 and 300 kg of dried maize. A farmer can build any size of box he wishes.

Size

Capacity of grain in dryer

1m x 1.5 m

80 kg

1m x 2m

105 kg

1.5m x 2m

150 kg

2m x 2m

210 kg

b) Natural Air Drying

Many farmers dry their maize using many different types of natural air drying methods. Each of these methods must let the air pass around the kernels to dry them. Therefore, to be completely successful the grains must be exposed to the air.

When drying maize this means that the husks, or leaves, covering the cob of maize should be removed. These leaves are bad for drying for two reasons:

- Leaves keep the air from directly touching the grain kernels. The moisture in the kernels is trapped inside and is more difficult to remove through the leaves.

- The leaves themselves also contain moisture which makes drying take longer and can spoil the grains inside.

However, many farmers like to keep the leaves on the maize cob because they feel that it protects the maize from insects. This is somewhat true. but many insects can still enter through the leaves and attack the grains.

It is impossible to. tell if insects are in the maize if the leaves are covering the cob. Also, if you wish to use an insecticide the leaves will stop the chemical from reaching the insects in the grain.

If you are drying the grain in the kitchen and the smoky flavour enters the maize then some leaves can be left to keep the smoke off the grain kernels.

If you do not remove the leaves from your maize during drying, then you can try an experiment of your own. Select 30 or 40 maize cobs and remove the leaves; leave the rest of your maize as before. Now dry the crop in your normal way. Check the maize often so that you can see which ones dry faster. Normally, the maize with the leaves removed dries faster and better then maize with the leaves covering the cob.

Eave Drying: With this method the maize is hung in bunches under the eave of the roof to dry. A few leaves are left on the maize cob, these leaves are used to tie the maize in a bunch. Then the bunches are hung from a pole under the eaves. Air can pass freely around the maize cobs. The eave keeps all rain water off the grains. Drying normally takes place over a period of two months in the highland areas.

The disadvantage of this method is that rats and birds can sometimes worry the grain. Also sometimes the farmer does not have space to dry his entire crop under his eaves.

Maize Crib Drying: See the Figures p. 162/ 163, taken from: African Rural Storage Center, IITA, Ibadan, Nigeria.

The maize crib can only be used for the dry season crop. However care must be taken to keep falling rain off the maize inside the crib. In the rainforest zone the crib cannot be used during the rainy season.

The Figures below are easy to follow. Remember that the crib should be 60 cm (2 feet) wide so that air passes through it. The floor should be one meter off the ground to keep rats from jumping up into the crib. Do not build it under a tree, rats can climb the tree and drop into the maize. Rat guards should be placed on all legs. The long sides of the crib should face the sun (east and west) so that the sun's heat is also used to dry the grains.

Birds and insects are hard to control with this drying method. Also, drying during the rainy season is very difficult.


Construction of a Maize Crib


Step 1: Dig the ground holes. Set the wall and floor supports


Step 2: Attach the wall braces and put the floor boards in place


Step 3: Tie the bamboo sticks to the wall supports. Attach a roof of zinc or thatch.

c) Direct Fire Drying

Kitchen Drying: Another effective way to dry grains is by placing the grain in the attic of the kitchen above the cooking fire.

In this case a few leaves can be left on the maize cob so that the smoke does not give the grain a bad taste, although some people like the smoky flavour. The heat and smoke can also keep some of the insects away. This method was developed during the pre-colonial times when all houses had grass roofs. The heat and smoke and moisture from the i grain easily passed out through the grass roof. However, with so many houses using zinc roofs today there is a problem. The heat and moisture are trapped under the zinc roof.


Drying in the kitchen

Zinc roofs trap heats and moisture; grass roofs allow it to escape

A few other problems with this method are as follows:

- As soon as the fire is put out and the smoke stops insects can fly back to the kitchen - they will leave only after the fire is started again. Space is limited under the roof - the capacity is often too small to dry the entire crop.

- Fire wood is very expensive.

Oil Barrel Method: A very fast drying method is with the oil barrel dryer. These are constructed exactly like Cocoa Dryers. However, the cost of the dryer, the cost of the wood to dry the grain, and the labour and time involved make this method too expansive for most farmers. Also the heat is often too high for the drying of rice, beans, and seed grain.


Figure

5.1 Difference between grain storage and grain drying

It is very important for farmers to realize that drying grain and storing grain are very different operations. Good grain storage techniques use totally different conditions and methods from grain drying methods.

A farmer should separate the drying of grain from the storing of grain. If you dry grain under the roof, in a drying crib, or under the eaves you should store the grain in a different place. The next section talks about Grain Storage Principles; examine them closely to see how they differ from the conditions for grain drying.

5.2 Grain storage principles

a) Conditions of the Grains

It was mentioned in Section 3.3 that only clean, unbroken kernels should be selected for storage. Now two other elements can be added to this list. The grain should be dry and it should be cool when it is put into storage.

b) Climatic Conditions

Grain stores best in weather which is dry and cool. Unfortunately, the weather is not always dry and cool. During the serious rainy season even well dried grain can become wet again if it is exposed to very wet air or rain. Since grain must be stored during all kinds of weather the type of storage method chosen must protect the grain from the worst possible weather conditions.

c) Store Conditions

A grain store must perform one task: the store must protect the grain from its natural enemies: mould and fungus, insects, rats, birds, and other animals.

To do this a grain store should have the following properties:

- The store must be dry.
- The store should be cool.
- The store should keep out the sun.
- The store should be clean.
- The store should have no holes or cracks in the roof, walls, or floor.
- The store might need to be treated with insecticide.

It is good to know why these six conditions should be followed. First, a good grain store should keep the grain cool, dry, and out of the sunlight because cool, dry grain respirates, or breathes, very slowly. The seed coat can resist mould and insect attack if the grain is kept cool and dry. Second' a grain store should be kept clean and in good repair (no holes or cracks in walls, etc.) so that insects and rats cannot enter or hide and live inside. Finally, the last item, some stores have to be treated with an insecticide to remove serious insect infestation. It is often difficult to control insects without using chemicals. This will be discussed in Chapter 7 on Insect Control.

5.3 Storage methods

a) Traditional drying/storage systems

Many farmers continue to store their produce in the drying place. Often the root or the eaves are still full with maize even after the produce has dried. Such practices are not correct grain storage techniques. In order to dry grain warm, dry moving air is required. However we have seen that in storage grain should be cool, not warm. Furthermore, if the drying air can pass around the grain kernels, then insects and rats can enter as well. Therefore it is best to transfer the clean, dry grain to a cool, dry place where rats and insects cannot follow. It is now time to look at some grain storage models which have been recommended for tropical farmers.

b) Drying Cribs

Many agricultural books say that the drying crib can also be used for a storage barn. However, as we have seen in the above section, it is too dangerous to leave the grain exposed to insects, birds, and other pests. After the grain is dry it should be moved to a better storage place.

c) Bag Storage

This is a very popular form of storage. Transportation of the grain is done in the same jute bag, the bags are easy to handle and the jute bag allows you to store different grains in the same room. The following principles should be kept:

- The storage room should be clean and free of all insects. Holes should be repaired.

- All old bags should be washed, shook out, and placed in the sun to dry to drive away any insects still in the sack.

- The bags of produce should be neatly stacked on wooden racks called dunnages away from the walls and off the floor. Grain bags should never lie on the floor or rest against the wall (see the Figure below). Water from the floor and ground can enter into the bags and cause spoilage.

- The bags should be regularly checked for any problems.


Sacks should never rest directly on the ground or against walls

The main disadvantage of jute bag storage is that the bag does not provide protection against rat or insect attack. Other measures must be taken to control these pests.

d) Bamboo Boxes

The box is constructed entirely of raffia bamboo sticks and bamboo rope (see the Figure below). The floor of the box is raised off the ground so that water cannot rise up from the ground and enter the box. The bottom of the walls are often packed with mud soil to discourage rats. The box has either a zinc/grass roof or is placed under the eaves of the house to keep the rain off the box.


Bamboo Box

Once the grain is well dried and cleaned it is placed in the box and a tight fitting bamboo cover closes the box. An average box is one meter long, one meter high and one meter wide - it can hold more than 300 kilos of maize on the cob. A well constructed box can last for more than 5 years.

Once it is well closed insects and rats cannot enter the box. However, the grain must be checked regularly for an increase in insect population 'from the eggs and insects which were carried in with the maize from the drying place. Inside the box it will be dry, cool, and dark. The box should be well cleaned at the beginning and end of each storage season. To use insecticide with this method of storage see Section 7.2.

e) Drums (Air Tight Storage)

A very good, but more expensive method is to use old oil drums. The drums should be well cleaned. All holes should be repaired and sealed properly with sodden.

Only very dry grain can be placed inside the drum; if it is too wet the moisture cannot come out and the grain can spoil. Once the dry grain is inside, the drum mouth should be sealed with wax or grease to stop air from entering. Very soon any insects inside should stop breathing and die because all the air is finished. Care must be taken to make certain that the drum is well sealed.

Finally, it is also very important to keep the drum out of the sun, in a cool place. Otherwise the hot sun hitting the metal drum will make the grain very hot. The grain will sweat and respirate faster. This also can cause spoilage. Therefore, always keep the drum under a shelter. An oil drum can hold almost 300 kilos of maize.

f) Others

Baskets, tins, and empty calabashes can also be used to store grain. Just ensure that the grains and the containers are clean and free of insects. Keep the container in a clean, cool, dry place. Baskets, tins' end calabashes are small and are ideal for seed storage. However, for large amounts of grain bigger containers are needed.


Metals drums must be put out of the sun. Good storage places are cool, dry, and dark.

6.1 Mould and fungus

As mentioned in Chapter 1 mould and fungus are serious pests of stored grain. They are very tiny plants which grow on the surfaces of grain. These tiny plants use the grain kernels as their "soil" or food supply. Moulds grow and multiply very fast on warm, wet kernels. If they become too plentiful they begin to spoil the grain as they cover it with more mould. The grain seed coat will change colour to a green or brown powdery covering. The grain often smells bad as well.

Some moulds and fungi give off a poisonous chemical which enters the grain. The poison is called aflatoxin. The aflatoxin can be harmful to humans and animals who eat the spoiled grain. Groundouts are attacked very easily by the fungus which make aflatoxin.

The best way to prevent fungus and mould attack is to harvest the crop at the correct time, dry it well and as fast as possible and then store the grain in a dry, cool place. The climate of the humid tropics is perfect for mould and fungus to live and grow. It is wet and warm for many months during the year. Farmers must be careful to protect their grain from the moulds and fungus.

6.2 Insects

Insects which attack stored grain are generally small - between one and 2.5 cm long. They have six legs, two sets of wings, and many have very strong chewing mouth parts.

These insects live everywhere: in stored grain, in the soil, in grass, in timber. Unfortunately, stored grain is their favorite food. Also, insects multiply very rapidly and can travel to where the grain is.

The following information about insects is helpful:

a) Life Cycles

Just as other animals, insects go through different stages of life. A fowl, for instance, goes from an egg to a baby chick to an adult chicken. Each stage is different from the other stages. Grain storage insects go from eggs to lane to pupa to adult. It is important for farmers to recognize these stages, which all lead to the adult insect.

Egg Stage: An adult female can lay between 100 and 450 eggs in a few weeks. Most eggs are too small to see. Some insects lay their eggs among the grains, others inside single grain kernels. The adult female will chew or drill small holes in the grain and then put some eggs in the holes, she will then cover the hole with a white coloured glue. The eggs and the hole are almost impossible to see. This is why even clean-looking grain can become infested inside a well sealed store. The eggs generally hatch after three to four weeks.

Larva Stage: When the egg hatches the larva emerges looking like a small white worm or grub with tiny legs. It begins to eat and move slowly about. Sometimes they come out of the grain to eat. After a few weeks the larva will begin to build a small nesting place (called a cocoon) with silky thread from its body. The larva will enter and begin the third stage.

Pupa Stage: The pupa stage is usually a time of rest before the adult stage. The pupa does not come out of the white cocoon: After two weeks or so the pupa sheds its skin and comes out of the cocoon as an adult.

Adult Stage: The adult stage of the insect is familiar to us all. The four principle grain insect pests in Cameroon are pictured in the Figure below.

Remember that insects lay many eggs. It is difficult to see eggs or larvae in the grain. If only a few adult insects are seen in the grain, it is certain that other insects in different stages are somewhere in the grain.


The Life Cycle of an Insect

b) Insects and Environment

Insects multiply fastest in warm temperatures and in damp or wet places. Normal tropical temperatures are ideal for insect growth. If the temperature is too hot insects will die. Remember that grain can be damaged at high temperatures as well.
Insects also need water or moisture. Wet grain or damp stores offer excellent places for insects to live and multiply.
Insects require air to breathe and food to eat. If a farmer can somehow control the insect's environment, temperature, moisture, air, and food then insect control is much easier. However, it is clear that tropical climatic conditions favour the presence of insects. This is why chemical control measures sometimes are required to stop insect attacks.


The Four Major Insect Pests of Stored Grain (enlarged and actual size)

c) How and When insects Attack Grain

Many insects, especially the Rice Weevil and the Grain Moth attack the grain when it is still in the field and not ripe. They lay their eggs in the grain at this time. The insects and eggs are carried into the drying place and store from the field. Other insects, like the Grain Borer, only attack grain once it is in the store. The adult has very strong jaws and can penetrate into very dry grain kernels. All of the above insects have the ability to attack and destroy sound, healthy grain they are called primary pests.

A secondary pest, like the Flour Beetle in our Figure, is an insect which can only eat grains which have already been attacked and broken into dust or flour by the primary pests, like the Rice Weevil. If Flour Beetles are seen in the grain it usually means that other primary pests have already attacked.

Adult insects can emerge at any time. However, large numbers usually begin to appear one to two months after harvest. At this time larvae could have been feeding unseen inside the grains. This is why regular inspections of the grains is so important.


Figure

d) How to Find Insects in Grain

Insects often sleep or hide during the day. Sometimes it is hard to find them. Here are a few ways to check your grain for insects.

Look for insects in the early morning or late evening, 7:00 a.m. to 7:00 p.m. The change in temperature and humidity at this time make insects to move about more.

If the grain is in bags take one bag outside and spread part of it on the ground. If there are insects inside the grain the heat of the sun will make them try to escape. Then they are easy to see.

Another method is to take a sample of grain and place it in a tin. Shake the tin vigourously for thirty seconds - any insects inside the grain will have been knocked out on to the bottom of the tin. Checking the grain for hot spots by thrusting your hand into the grain can point out danger areas in the grain store. Insects make the grain hot.

Stored grain should be inspected weekly for evidences of insects so that control measures can be taken quickly.

(introduction...)

Now it is time to look at measures which can be taken to control insects in stored produce.

7.1 Traditional methods

a) Sunning

As we have shown insects cannot live in very hot conditions. Placing grain in the sun will heat it above 40 °C - this will drive off all adult insects. However, the eggs and larvae are sometimes left unharmed because they are living inside the grains. The heat does not touch them. Even if all the visible adult insects have left the insect problem will return as soon as the eggs and larvae living inside the grains develop into adults.

b) Wood Ash Control

Farmers often mix wood ash (ashes from fire) or sand with the grain when they store it. This sand and ash can scratch the insect's skin. In well dried grain the water in the insect's body will all come out through the cuts in the skin. The insect will die. Furthermore, insects find it difficult to move over grains that are mixed with sand or wood ash. The usual dosage for this kind of treatment is one kilo of sand or ash to 15 or 20 kg of grain.

c) Smoking

Farmers who dry maize above the cooking fire find that the smoke keeps insects away.
However, the rice weevil can fly away from the grain while the fire is smoking. When the fire is out the insects can return. One way to control this is to keep the drying place far away from the grain fields - then the insects will find it difficult to fly back and forth between the field and the drying place (see the Figure above).

d) Using Special Plants

Many farmers have found certain local plants which control insects in stored grain. When these plants are properly dried and mixed with the grain, insects do not like to remain in the storage place. Fresh cypress branches placed in between layers of grain in a bamboo box or oil drum also worry insects. You should check through your farming area for other plants and leaves which can naturally control insects in stored grain.

Most of the local, traditional techniques do not kill insects or larvae or eggs. They drive away adult insects. Also these methods do not have the power to remain for long - insects can return as soon as the smoking or sunning is finished.

7.2 Chemical methods

Given a tropical climate, which favours large, rapid insect development, and the inability of many local insect control techniques to halt insect attacks, chemical use is sometimes the only way to control insects.

7.2.1 What are Grain Storage Insecticides?

Insecticides are chemical poisons made by man to control insects. All insecticides are made up of at least two elements. The first is the poison itself which is called the active ingredient. It is the dangerous element which actually kills the insect. Different insecticides have different amounts of the poisonous active ingredient inside. The second element is called the carrier. The carrier is a neutral dust or liquid which is mixed with the active ingredient. The carrier helps to spread the poisonous active ingredient evenly over the object to be treated. All insecticides have some poison and some carrier in them. These chemical insecticides are specially made in factories to kill insects, but they can also harm humans! It is very important to only use the chemicals which are correct for the specific job of grain storage protection.

There are hundreds of insecticides which kill insects. However only a very few of them can be used to protect stored food which will be eaten by humans. Grain storage insecticides are very special and very few. Two safe chemicals for use on stored grain are Malathion and Actellic. No others should be used to put on good grains.

Malathion is also called Zithiol and Malagrain. These are other names for Malathion. Actellic is only known by its own name.

Both Malathion and Actellic come in three forms to be used on grain.

a) Powder or Dust Form: These insecticides are already mixed and diluted in a dust carrier - all that muse be done is to mix them directly with the dry grain you do not have to do any other preparation.

b) Wettable Powder: These chemicals are in a powder form. They must be mixed with water and sprayed on walls of grain stores. They should not be sprayed on grains themselves.

c) Liquids: These chemicals are in liquid form and must be mixed with water before they are ready for use. Use this mixture on walls of grain stores.

These are the three types of Malathion and Actellic. Make certain that you only use the dust or powder form (a) on the grains. Items (b) and (c) should be used only to treat grain stores.
You can now see that chemicals are complicated things. Do not use any chemical which you do not understand.

7.2.2 How to Use the Chemical

a) Handling the Chemical Before Use

All chemicals should be locked in a safe place out of reach of children.
Actellic and Malathion should be kept cool, dry, and out of the sunlight. Moisture, sunlight and heat make these chemicals to lose their power fast.
Read all directions carefully before use. Only adults who understand the chemicals should handle or use them.

b) When to Use the Insecticide

You should only use chemical insecticide if there is no other way to control insects. It is safer to use one of the traditional insect control measures which was outlined above. Only if these ways fail should the insecticide be used.

Once you have determined that you need to use the Malathion or Actellic it is important to use them at the correct time.

- Apply the insecticide before the insects become too plentiful. It is more expensive and more difficult to kill all insects in badly infested grains than it is to keep insects out of grain.

- Only apply the Malathion or Actellic to dry grain in the storage place. Do not apply them to wet grain - remember that Malathion and Actellic lose their power quickly if they are exposed to sunlight heat, and moisture.

- Apply the chemical when you move the grain from the drying to the storage place. It saves labour this way and the grain has to be moved and mixed only once.


7.2.3 Instructions for Use

a) How to Prepare Yourself Safely

- Wear clothes that cover all parts of your body (see the Figure below taken from a publication of the Ministry of Agriculture, Section of Food Products and Extension, Managua, D.N., Nicaragua, C.A.). Trousers, not shorts, shoes, long sleeved shirt, gloves, and hat should be worn.

- Wear a mask or a wet rag piece around your face.

- Do not smoke or eat while you use the chemical.

- Read and understand all instructions on the label before you begin.

b) Treatment of Stores

- Do not treat stores which are in your cooking kitchen or actual parts of a house when people live there.

- All stores should be swept clean of dirt, dust, and other trash. The trash will block the chemical from reaching insects.

- The wettable powder form should be used. Read the directions carefully. Make certain that you mix the correct amount of Actellic or Malathion with the correct amount of water.

- Spray the walls and floors of the room or store evenly.

- Leave the room immediately. Close all doors and windows of the store. Do not pack produce inside for three (3) days.

Remember if your grain store is in the cooking house or in your sleeping house do not spray the room. The chemical can bother children.

c) Treatment of Grain

Once again prepare yourself correctly as explained above and as shown in the Figure. Make certain the grain is dry and the storage area clean. The Actellic 2% Dust or Zithiol, Malathion or Malagrain 2% Dust should be used. Use no other chemical on stored grains. Follow the instructions carefully do not exceed the stated dose.


Figure

d) Treatment of Bagged Grain

It is best to mix the insecticide dust with the grain before the bag is full.

Zithiol, Malagrain and Actellic 2% Dust is mixed as follows:

40 g of dust for 100 kg of grain or 2 level tablespoons of dust per 100 kg sacks of grain (2 tablespoons of the insecticide dust = 40 g).

Fill the grain sack about one half full. Put in one tablespoon of powder. Shake the bag well and stir the grain with a bamboo stick. Fill the rest of the bag and put the other tablespoon of dust on it. (This makes 2 tablespoons to a 100 kg bag.) Once again stir the grain with a bamboo stick so that it is mixed well with the chemical. Pack the bag on the dunnage in a cool, dry, dark place.

Burn or bury all empty chemical containers. Wash your hands thoroughly. Wash your clothes after you are finished. The treated grain should not be eaten for at least one week. After one week it is safe for human consumption.

Before you prepare the grain for cooking, sun it for a few hours or sift it well.

e) Treatment of Bamboo Boxes

In this case the maize is usually on the cob. The 2% Actellic or Malathion Dust should be used. The dust can be applied between layers of the maize cobs. The same dose is followed:

40 g of dust for 100 kg of grain or 2 level tablespoons of dust per 100 kg of grain.

However 100 kg of grain when it is on the cob takes up more space than 100 kg of shelled maize. In fact, 100 kg of cob maize fills two and a half (2 1/2) jute bags.

To apply the Actellic or Malathion in a bamboo box one should sprinkle a tablespoon of the dust on the floor of a bamboo box which has been well cleaned. Then 2 1/2 jute bags (100 kg) of dry maize cobs are put inside. Two tablespoons (40 g) of the dust are evenly sprinkled over the top. Now another 2 1/2 jute bags (100 kg) of maize cobs are put on top of the treated layer of grain. Two more tablespoons of dust are applied. Go on putting maize and insecticide dust into the box layer by layer until the box is full.

- Once again, burn or bury all empty containers.
- Wash your hands and clothes after the application.
- Let the grain stay for one week before you eat it.
- Sun the grain for a short time before preparation.

Actellic usually can keep all weevils away from the grain for about five to six months. Malathion (Malagrain or Zithiol) protects grain for about four months. Make certain that the dust is mixed well with the grains. Check your grains and store often to make certain that all is well.

Always follow all instructions. All chemicals are dangerous and should be handled very carefully by adults who understand what they are doing. If you do not understand how to use the insecticide do not use it. Go to your Agric. Field Worker or Chief of Post for assistance.

(introduction...)

Rats are probably the most destructive and dangerous pests. Not only do they destroy grain in the field and in the store; but they damage buildings and carry diseases and sickness into the grain as well. Learning to control rats is very important.

8.1 Some facts about rats

There are many different kind,s of rats. Rats are actually a member of the rodent family. Other rodents are squirrels and mice. When we speak of grain storage rats we also include the very small rats called mice inside the group.

Rats are everywhere, in fields, in the ground, in houses, and in grain stores. Rats travel very rapidly ,and go long distances to find food. Rats can force their way into buildings, homes, and grain stores to get to food. They can dig under foundations and chew through wooden walls. They can squeeze through holes the size of a very small coin piece. Rats can also climb very well - sometimes up a vertical wall or metal pipe. They can jump very high - almost a meter. Rats multiply very fast. A pair of rats can produce between 700 and 1000 baby rats each year. One rat can eat 25 kg of grain in a year. Looking at some of the abilities of rats it is easy to see why controlling them is so difficult.

8.2 Environment and habits of rats

In order to control rats a farmer must know what they like and how they will react to their environment.

First of all, rats need food and water. They also like cool, dark places. Lights hurt their eyes and frighten them. Rats will build their nests and hide behind large objects, next to walls, in corners, and under floors.

Rats also travel over the same path each time they go to search for food and water. They travel next to walls. Rats cannot see well they must feel and smell their way - touching the wall with their whiskers and hair to know the roads.

Rats usually move about at night - beginning in the late evening around 7:00 or 8:00 p.m. continuing until midnight. Rats are cautious and shy. If they see or meet a new object or food they will not touch it or eat it until they become used to it.

Now that you know a few of the characteristics of rats it should be easier to follow and control them.

8.3 How to find rats

Here are a few hints about where rats can be found. First, look for their droppings or excrements. They should be looked for in places that they like: along walls, in corners, near grain, behind equipment, etc. If you find droppings this means that rats like the area. This is a good place to put traps.

Look for the damage that rats cause. This means check for chewing or gnawing teeth marks on wood or in grain stores. You can also look for their trails or paths. Rats travel over the same path, so after a few days their foot prints in the dust or a path in the grass can be found.

Rats can be heard at night when they move around and chew. It is important to be able to know where rats are - this way you can set your traps in the correct places.

8.4 Non-chemical rat control methods

It is very important to keep the storage area clean. Sweep up all dust, dirt, trash, and old grain or food. Rats like dirty places. Keep the grass cut short around the buildings; rats like long grass to hide in. Remove all old equipment and trash from the storage area this makes it more difficult for rats to hide.

Repair all cracks and holes in the buildings. Make the rooms "rat-proof". The doors and windows should be tight fitting so that rats cannot slip inside.

All drying cribs or granaries should be a meter off the ground and the leg poles protected with rat guards. This way rats cannot jump or climb into the store.

Pack mud at the base of a bamboo box store rats do not like mud like this.

Use rat traps. The spring or snap type is best. Set rat traps in the places where rats like to go; along walls, in corners in front of holes, etc. Make certain that the traps are sound and not rusty. Hide the trap well.

Put some food which rats like on the trap so that the rat will walk onto the trap (fufu and sugar is good). Remember that rats fear strange, new objects or food. Therefore, put food on the trap for two or three days before you set it. The rat will get used to the trap and the food. After the third day set the spring - the rat will not fear the trap it will be very surprised to find the trap to be dangerous. Cover the trap with straw or grass, let only the food show.

Check your traps daily. Remove dead rats immediately. Change the position of the trap after you have killed a rat in the former place.

About ten traps are needed to control rats in a two room house. This is expensive. Rats are very smart sometimes and will not touch the traps at all.

Another method is to set a bucket half-filled with water in a place where rats are. Balance a narrow stick over the bucket. Put some food (corn and sugar) as bait on the end of the stick. The rat will walk out on the stick to get the food. The stick will tip the rat into the water and the rat will drown. Make sure that the stick is very lightly balanced over the water bucket.

Traps are safer than poisons and should be used in homes where there are children who could get into the poisons. However, rats learn how to avoid traps, and traps are expensive. Sometimes rat poisons need to be used - only use them when absolutely neccessary.

8.5 Chemical rat control methods

Using rat poisons to control rats is usually cheaper and more successful than trapping rats. However, all rat poisons can also poison humans and other animals. Farmers must realize that these chemicals are very dangerous Only those farmers who can control their children and animals should use rat poison. If there is any doubt in your mind about using these poisons safely and correctly then they should not be used.

a) What are Rat Poisons?

The rat poisons on the market today are usually anticoagulant poisons. This means that the poison attacks the blood of the rat. The poison acts very slowly and the amount of poison inside is small so that the rat cannot taste or smell it. The rat does not know that there is poison in the food. The poison makes the rat slowly bleed inside its body until it dies. The rat must eat the poison two or three times before it will die. It is best to buy the rat poisons from a pharmacy or a cooperative store. The poisons sold by the traders in the market are not safe.

b) When to Use Rat Poison

Once you discover rats the poison baits should be used very soon. It is very hard to control large families of rats. But keeping a few rats under control is much cheaper and easier. (Remember that a family of rats can grow to 700 or 1000 in a year.)

c) How to Use the Poison

The poisons come in many forms. Some are already prepared baits. These contain a food which rats like, rice or maize, which has already been mixed with the poison. It is ready to use. Sometimes it is good to add a little sugar or palm oil to the bait to make it even sweeter to the rats.

Other poisons come by themselves as liquid or powder and you have to mix the poison with a food the rats like. Follow the instructions for mixing very carefully. If you mix too much of the poison with the food the rats will smell the poison and not eat it. Be very careful when you mix the poison wash your hands with soap and water after mixing poison.

d) Placing the Baits

The poison should be put in places which rats like (see the Figure p. 179) but put in a place where animals and children cannot touch them. Pipes, bamboo sticks, tins, and tires offer good places to hide poisons. Place these containers along walls, in corners, behind doors and equipment, around grain bags, etc., all the places where you find signs of rats.

Goats and chicken cannot get into the small containers and rain will not wash the poison into the ground if these containers are used.

A box with one small hole in each end with poison inside is a very good bait setting. Rats like dark, quiet places such as boxes.

The bait stations should be checked daily and refilled when they are eaten. Fresh poisoned food should be used. The poison should be left out at least two weeks so that you are certain that rats have all tried to eat the bait.

Remember:

- Read and understand all instructions.
- Do not smoke or eat while mixing or using the poison.
- Wash your hands very well after using the chemicals.

- Bury or burn all dead rats people or animals eat rats killed by poison they too can get sick and die.
- Burn or bury all empty chemical containers. They cannot be cleaned out correctly. Do not use them for other purposes.
- Keep all these chemicals locked in a cool, dry, dark place which is out of the reach of children. Make certain that the containers are well labeled and marked as dangerous.

Once again never use rat poisons where children or animals can get them. These poisons can kill humans and animals. Always be careful to follow the instructions.


Rat poisons should be placed in dark places. Make certain that children and animals cannot touch the poison

9. Costs and benefits of improved grain storage: an example

Now that the techniques for protecting your stored grain have been presented it is time to show how a farmer can try and calculate the costs and benefits of these techniques him/ herself.

We have already shown in Chapter 1 that the cost of grain losses can be high. But the farmer should be able to decide for him/herself whether or not these methods of pest control are worthwhile. The following method is simple, but helpful.

To begin with the farmer should try and get a general idea of how much is lost to moulds, insects, and rats each year. Most good farmers already know how badly they are affected by the enemies of stored grain. Then it is necessary to calculate the cost of improving the grain storage methods now being used. The farmer should then compare the amount or cost of the damage done each year by grain pests to the cost of using the methods mentioned in this manual. The farmer can then decide which is better: losing the grain to grain pests or spending a little more to stop the losses.

An example will help to show how to do this. Let us look once again at our friend Mr. Ngwa of MBali.

Mr. Ngwa knows that he loses about 100 kg of maize each year to rats and insects. Rats also destroy about three jute bags a year. The jute bags cost 250 francs a piece. Three jute bags cost 750 francs. His 100 kg of maize are worth 5000 francs. Mr. Ngwa loses about 5750 francs a year to grain pests.

Now it is time to calculate the cost of controlling the pests which destroy his grain. The following list was made by Mr. Ngwa. It contains all the necessary items to improve his present system of storing grain.

a) Actellic Insecticide 2% Dust: He should use 40g per 100kg, he has 1000kg; 400g cost

600 frs.

b) Actellic Insecticide: One packet of wettable powder to spray walls

100 frs.

c) Rat traps: 4 traps at 300 francs each

1200frs.d)

Wood to patch holes in his grain store

300 frs.

e) Zinc piece to patch holes and rat-proof the door

800 frs.

f) Other: nails, etc.

100 frs.

Total cost

3100frs.

He will spend about 3100 francs to control the pest which destroy about 5750 francs worth of his grain and jute bags. This means that his benefit will be equal to the value of the grain he saved less the cost of the improvement or 5750-3100 = 2550 frs.

Furthermore, his store will still be in good repair for a few years and his rat traps can be used for a number of years as well. The zinc, wood and rat traps are one time payments. Next year Mr. Ngwa will pay only the 700 francs to buy the Actellic. Now his "savings" or benefit will be 5750 less 700 frs. for chemicals. A total of 5050 francs should be gained in the next year.

Not every farmer will benefit as our friend Mr. Ngwa. However, each farmer should calculate how much it will cost to reduce his losses of stored grain. Farmers might find that it is very worthwhile to practice good grain storage techniques.

10.1 Present state of tuber storage

Many farmers grow and eat more tubers than grains. This is especially true of the people in rain forest areas. The principal tuber crops are cocoyams, yams, cassava, and sweet potatoes, with some production of Irish potatoes in the higher parts of the highlands. Although all of these tubers are quite different from each other, they do have similar characteristics when they are in storage. Therefore, when this chapter speaks of tubers in general, it is speaking of the five types of tubers mentioned above.

Whereas the different kinds of tubers act almost the same in storage, storing tubers and storing grain is very different. Grain is much more durable during storage and transport. Tubers, on the other hand, bruise, cut, and spoil very easily. As experienced farmers know, it is much more difficult to store tubers successfully.

Tubers do not have as many different kinds of enemies as stored grain. However, tubers are delicate and so easily attacked that only a slight wound or cut can spread disease all through the tuber and spoil it totally. In storage the major pests seem to be:

- mould and fungus (which cause rotting and spoilage),
- insects (the weevil),
- rats.

Insects and rats do not seem to be as serious pests as they are in stored grain. Nevertheless, the problem with fungus and mould attacks are serious and widespread. There are no accurate figures for the amount of tubers lost or damaged during storage and transportation, but tuber losses are probably higher than grain storage losses. A reliable estimate of stored tuber losses would be about 15%.

The large losses of tubers after the harvest often discourages farmers from growing more. Most farmers grow enough for their families' needs, with only a small surplus, if any at all, for emergencies or for the local market. Prices of tubers rise every day because quantities of tubers are small in the markets.

With the present problems of tuber storage bothering most farmers, it would be difficult to convince farmers to increase their tuber production. They would lose too much after the harvest to make it worth their while.

Not only would better storage methods help farmers to produce more, but the quality of tubers in the market would improve. Spoilage would be controlled. Farmers could grow and sell more. The large price increases during the scarce periods would be reduced. These developments would benefit both the farmer and the consumer.

10.2 What happens to tubers in storage

It is important to understand how tubers change during storage and what actually happens to them when they spoil. If farmers can understand these changes they will also see how some of the improved methods can work to avoid the problem of spoilage.

A tuber, whether it is a yam, cocoyam, cassava, or potato, is a very starchy, fibrous root which can be peeled and the flesh inside prepared and eaten. In storage the two basic parts which concern us are the skin and the starchy interior or flesh..

- The skin is the thin outer covering which surrounds the tuberous root. In cassava and cocoyams it is a layered, corky skin, while with potatoes and yams it is not as thick. The skin is the weakest immediately at harvest time. It cuts and bruises easily. Also moisture and air can move freely in and out through the skin. The skin provides no protection against insects or rats. However, a sound, uncut skin can resist moulds and fungus better.

- The fleshy interior makes up over 90% of the tuber. This is the stored food of the tuber. It is a root or stem of the tuber plant. This is the part which is eaten. Each tuber species and variety has its own distinctive colour, taste, and texture. However, in general the flesh is starchy and moist. Just under the skin the flesh is sometimes tougher. But it cannot protect itself against cuts, insects, or fungus and mould.

Tubers are living things. While in storage they must be kept alive. If a tuber ceases to live it will begin to spoil immediately. What does it mean when we say, "The tuber is alive"?

First of all the tuber is breathing: Just like other living things, it takes or breathes in oxygen from the air and uses it inside its body, in this case the fleshy interior. To complete the breathing process the tuber must give off or breath out the air that is used. This used air is called carbon dioxide.

Secondly, to stay alive the tuber must ´'eat'' or nourish itself. When it breathes in air it also consumes a tiny part of its stored food in the fleshy part. When it consumes or eats part of this food it gives off heat and moisture as wastes.

The entire process of breathing in air and consuming its stored food and then giving off used air carbon dioxide - and heat and moisture is called respiration.

All living tubers, even in storage, respirate. For safe storage the tuber should respirate slowly. Therefore the good tuber store will have the ability to make the tuber "breathe" at a very slow and steady rate. Now we will look at the conditions which control this important rate of respiration.


A living tuber respirates

Moist, warm places make tubers respirate faster. A very cool, dry storage place keeps the tuber living and respirating, but at a very slow rate. If the tuber is cool and dry it is taking in a small amount of oxygen from the air and is using or eating only a very small amount of its stored food. Therefore, it is giving off or breathing out only a very tiny amount of heat, moisture and carbon dioxide, the used air. This is a good storage situation.

If the tuber is packed in a warm, wet place it begins to wake up and breathe in more oxygen and burn up more of its food. This makes the tuber give off more carbon dioxide, heat, and moisture, which makes the tuber even wetter and warmer. This will make the tuber respirate even faster again. Soon, this process of faster and faster respiration can cause the tuber to spoil.

To better understand why fast respiration is not good for tuber storage one should look at what really causes the tuber to spoil.

Tubers spoil because they are attacked by moulds and fungus which feed off the tuber's flesh and eventually consume or contaminate the tuber until it spoils.

Moulds and fungi are tiny plants which grow and multiply very rapidly on all kinds of objects: wood, grain, plants, clothes, and stored tubers. Since moulds are a special type of fungus which is still very similar to a fungus we will call all of this type of pest a fungus. Fungi are plants which cannot make their own food. They must grow on an object which can supply them with their food. Fungi are everywhere. They grow and multiply best under warm, wet conditions. Fungi do not spread in cool and dry places. The tropical climate is perfect for the growth of fungi. It is warm and wet many months during the year, especially in the rain forest zones.

Fungi are spread by the wind. An adult fungus plant will release thousands of tiny seeds, called spores, into the wind. These seeds or spores are so tiny that the wind carries them everywhere. Only a few spores will find warm, wet places. They will grow and multiply very rapidly. This is when fungus becomes dangerous.

When fungi begin to grow on a tuber, for instance, they respirate as well. This means they breathe in air and they consume part of the tuber's stored food. Then the fungi give off heat, moisture, and carbon dioxide. Many fungus plants are poisonous. When they begin to grow on an object they can contaminate it with their poison. If humans or animals eat the contaminated thing they can get sick.

Tubers are easily attacked by fungi. The protective skin is very thin and weak. It cannot resist fungi. If the tuber is cut or bruised the tuber's wet flesh is exposed to the air. The fungi spores (seeds) will grow very rapidly in the moist flesh of the tuber. The fungi will respirate quickly, giving off heat and moisture as it grows. This makes the tuber respirate even faster, making it warmer. This allows the fungi. to multiply even faster. Soon they have spread all over and even in side the tuber. The tuber gets discoloured, black streaks and stains running all through it as the fungus begins to cause the tuber to rot or spoil. Very soon the fungi can even spread to another tuber in the store. The whole process can be repeated until many tubers are suffering from rotting and spoilage caused by the mould and fungus at" tacks.

As you can see, tubers are very delicate and once they are wounded either by insects or rats or man, they can be attacked and easily spoiled by fungi. This must be avoided at all times if safe storage is to take place. Tubers must be handled carefully from the moment of harvest to the time of consumption if spoilage is to be avoided.

10.3 Preparing Tubers for Storage

a) Harmful Harvest Techniques

As we have shown, tubers are very delicate food stuffs. The most vulnerable stage of the tuber's life is just when it has been harvested. At this time the skin, especially of the sweet potato and yam, is the weakest. The following practices at harvest time are very harmful to tubers which are to be stored. If the harvesters knew that what they were doing was harmful to the tuber they might change their method of harvesting.

- Careless removal from the ground: When the tuber is moved from the ground at harvest it is often cut with the cutlass or other digging tool. Even stones can cut or bruise the skin when the tuber is being removed. When the crown of the yam head is removed with the sett stem piece make certain that the cut is clean and not too deep.

- Packing the tubers in the field: Once the tuber is lifted or dug from the ground many harvesters carelessly throw or drop the fresh root into the carrying baskets. Even a short drop of 30 cm can bruise a potato enough to make it spoil after two weeks of storage. Potatoes, cassava, and yams are especially sensitive to this type of rough handling.

- Exposure to the sun and rain: Tuber harvesting often takes all day long. As they dig the tuber roots many farmers leave the fresh tubers lying in the sun. This sunning is bad for freshly dug tubers, especially Irish potatoes, sweet potatoes, and cassava. The white flesh of the Irish potato turns green just under the skin. This makes the potato bitter. Exposure to the direct sunlight makes the tubers lose too much water too fast. This is bad.

In the same manner, rain can quickly damage freshly dug tubers, especially yams and cocoyams. Fungus attacks can begin immediately after rainfall has wetted the tubers. The wet skins can be penetrated very easily and they take a long time to dry out.

Farmers should avoid doing these careless practices which harm tubers before storage even begins.

b) Some Harvesting Hints which Aid Storage

Be careful not to cut, bruise, or wound the tubers when they are dug up. When white yams are harvested wood ashes (ashes from fire) should be rubbed onto the cut which was made on the tuber's crown when the tuber was removed from the yam plant.

Cocoyams and cassava should be cut away from the stem so that a part of the woody stem is attached to the root. This way the tender flesh is not exposed to the air.

All cuts should be rubbed with wood ashes as soon as possible. This makes it difficult for fungus to attack. Wood ashes are very dry. Fungus cannot grow well on wood ashes.

Line the carrying basket with grass and leaves. This makes the basket soft. Place each tuber in the basket gently. Do not throw or drop the tubers inside the basket. If there is time cover each layer of the tubers with grass so that the next layer of tubers does not touch the bottom layer.

Harvest on dry days. Do not let the rain fall on the fresh tubers. Also do not let the sun shine directly on the harvested roots. All full baskets and piles of tubers should be shaded from the sun. The sun and rain can harm the freshly harvested crop.

Clean all dirt and debris from the tubers. Make certain that the tuber is well cleaned. Insects, fungi, and other diseases can hide in the dirt and be carried to the storage area if the dirt is not removed.

Get the tubers to the storage area as fast as possible. Leaving the tubers outside where you cannot control the weather or the fungus is dangerous.

The hints given above can do all to make certain that the tuber is correct for storage. Most losses of stored tubers occured because the tuber was not properly handled or prepared for storage. It is wise to be very careful when handling tubers.

c) Curing the Tubers

Some tubers can store better if they are cured before they are stored. This is true of the Irish potato and the sweet potato. Sometimes yams (especially the white yam) can benefit from three days of curing. Curing is a process of resting under certain conditions which will make the tuber's skin get a bit thicker and tougher. This makes the tuber store better.

Potatoes should be spread out in a shaded, cool dry place where air breezes can pass. They should not lie on the earth or touch each other. After one week or so the potatoes can be put in the storage place.

Yams should be treated like this for about two days, followed by one day in the sun for four hours, turning the yams occasionally, to complete the curing process. Then place them in storage.

d) Selection of Tubers for Storage

This is one of the most important elements in tuber storage. It is very true that one bad cocoyam spoils all the achu. Diseases can rapidly spread from one tuber to another inside the tuber store.
Therefore, all tubers which are diseased, infested by insects, or have a portion of their root spoiled should not be chosen for storage. Also, all tubers which are cut, bruised, or wounded should be separated from those tubers which will be stored. The unsatisfactory tubers should be used as soon as possible. It is this selection process which can save you many lost tubers.

e) Transportation

A few words about transporting tubers could be useful at this time. Follow the same rules about tuber handling at harvest time when you transport the tubers.

- Always handle them carefully. Small bumps or drops can bruise or cut the tuber. This will open it up for attack by fungus. Do not throw or drop tubers while loading or unloading them.

- Avoid sunlight and rain. The tubers should be well covered so that sunlight and rain cannot strike them.

- If you are carrying a very large load of tubers in a lorry or a pick-up it is a good idea to make a soft bed of grass and sticks on the floor of the lorry so that air can pass under the tubers and bumps on the road do not damage them. Also, do not pack the tubers more than two or three feet (60 or 90 cm) high without putting a layer of grass and leaves in between so as to provide a cushion for the tubers.

Following these basic principles will make transporting tubers a safer operation.

10.4 General storage principles

In general, all tubers store best under similar conditions. However, there are a few differences which should be noted. Therefore tuber storage principles will be talked about under three groups. The first group will be sweet and Irish potatoes, the second group will be yams and cocoyams, and finally, cassava storage will be discussed.

a) Sweet Potatoes and Irish Potatoes

Once the curing and selection process is finished the. potatoes should be kept under the following conditions:

- dark,
- dry,
- cool,
- ventilated.

Sweet potatoes do not store as well as Irish potatoes. Many people leave sweet potatoes in the ground until they wish to eat them. This does not work very well during the rainy season. The Sweet Potato Weevil is a serious pest in some areas which makes it difficult to follow the practice of leaving the potatoes in the ground until they are needed.

In the store the potatoes should not be piled too high on top of each other. One meter is the limit. Potatoes can be stored in cold storage or refrigerators.

The store should be dark, dry, and cool because it is hard for fungus to live in these conditions. Also, the tuber respirates in dry, cool, dark places. The store should be ventilated so that when the tuber gives off heat and moisture during respiration the air can pass and carry it away. The potatoes should not lie directly on the earth floor - water can come and spoil them.

b) Yams and Cocoyams

The main principles to maintain in yam storage are the same as for potatoes. The store should be:

- dark,
- dry,
- cool,
- ventilated.

Such a store keeps the yams and cocoyams respirating slowly and it makes it difficult for fungus and disease to enter. The ventilation makes it possible for the air to keep moving away any heat which is given off during respiration.

Whereas potatoes can be laid on top of each other up to one meter, yams do not store well when they are touching each other. Yams should not touch or lie on each other in storage. They do not dry evenly and air does not pass as well when the yams are piled like this. Yams and cocoyams should not lie directly on dirt floors.

In most cases cocoyams do not store as well as yams. However, this varies as to the locality and the species of cocoyams and yam.

Yams are also left in the ground in many areas and harvested upon need. However, the success of this method depends on the local problems with pests in the field: monkeys, insects, rats, and termites. This practice apes not succeed during the rainy season once the tubers are mature.
Usually yams which take the longest time to mature and are harvested late have the strongest flesh and seem to store better. The white yam and the yellow yam store better than the water yam and the Chinese yam.

c) Cassava

Cassava is very difficult to store. Cassava tubers generally cannot last more than a few days once they are harvested. It should be left in the ground and harvested as it is needed. The best way to preserve cassava is in the form of gari.

10.5 Tuber stores

There are so many different types of tuber stores which are used locally throughout Africa that to talk about them all would be impossible. Here are three methods which are fairly common. Most other stores use the same principles.

a) The Yam Bam

This store is a small simple building with a thatched roof: zinc roofs are sometimes too hot. The walls can be of any construction: wood plank, bamboo, etc. Mud blocks or mud packed walls are preferred because they keep the inside of the barn much cooler. The floor should be raised off the ground about 30 cm. This allows air to pass all through the barn. The floor can be made of bamboo or wood.

There should be small spaces in the walls or under the eaves to let the air pass freely through the barn. Tubers are generally spread evenly on the floor. Make certain that the barn is filled carefully so that the tubers are not damaged.

An improved method using the same store is to build bamboo racks or shelves along the walls of the store. The tubers are then placed on the racks. The racks or shelves should be constructed at 60 cm (2 feet) intervals along the side of each wall. This way each wall would have about four racks attached to it, all spaced 60 cm from each other.

Yams, cocoyams, and potatoes would store well in this manner. The tubers would not be piled up on top of each other. They would not be touching each other. Disease could not spread. The room is cool and dry and the sun cannot enter. Furthermore, air can pass all around the tubers to keep them cool. The tubers can be easily inspected for insect or disease problems as they are not piled on top of each other. The barn can be locked at night to discourage thieves.

b) Clamps or Tuber Pits

This method is used mostly for potatoes. It does not seem to be as successful with yams.

A shallow hole is dug in a shady, cool place. The hole is then lined with sand. Grass, leaves, and sticks are then packed over the sand. The tubers are then carefully placed in the hole and covered with ashes or sand. Grass and banana leaves are then placed over the filled pit. A small sun/rain shelter of bamboo and thatch is built over the clamp. One must make certain that the drainage is good so that water does not fill the pit and spoil the tubers.

This method keeps the tubers cool, dry, and dark. However, there is no ventilation. If heating takes place the heat cannot escape. Instead it will build up inside the pit and could cause spoilage. It is also difficult to inspect the tubers for storage problems. Termites could bother the pit if they are a problem in your area. The wood ashes sometimes discourage them.

c) Box or Basket Storage

Tubers, especially the potato, can be gently packed into baskets or boxes and then stored in a cool, dry place in the house. Sometimes it is good to pack the tubers with wood shavings, sand, or wood ashes. This not only cushions the tubers, but it also stops the spread of fungus diseases.

Make certain that the box has a few holes in it so that air can circulate. A basket should have a loose weave. The major difficulty is that the tubers cannot be easily inspected. The area is small, not too many tubers can fit into a box or basket.

10.6 Storage pests of tubers

We have already discussed the rotting and spoilage problems caused by fungi and moulds. Now the insect and animal pests will be discussed.

The major insect pest of the potato tuber is the Sweet Potato Weevil. It looks like the Rice Weevil shown on p. 170. The weevil often begins to attack the tuber in the ground before it is harvested. Then, when the tuber is carried to the store, the larvae, eggs, and adults are all carried to the store. Once in the store, they move into other tubers and spoil them. This weevil makes tiny, hard-to-see holes in the skin of the potato. However, fungus and other diseases can enter easily through this holes.

The best control method is to rotate the crop every two years so that the eggs which are laid in the soil will not find food when they hatch into larvae. They will die and soon the field will be free of the pest. Harvesting earlier than normal is helpful. The weevil likes mature, ripe sweet potatoes. Leaving the potatoes in the ground can be dangerous - the weevils can fly to fields where they know the potatoes are growing.

Insecticide - Malathion or Actellic - can be used if it is necessary. Check up in section 7.2, for information about chemical control of the Sweet Potato Weevil. The same rate of application should be followed with sweet potatoes as with grains.

Yams sometimes have a problem with termites in the field. Harvesting earlier is helpful. In storage yams sometimes are bothered by a weevil entering the tuber through the cut crown (where the sett was taken from). Rub wood ash on the cut before you store it. This helps to keep the cut free of fungi and insects.
If rats and other animals bother the tubers, trapping or harvesting early is the only control method.

References

Part I: Farming Methods

American Society of Agronomy (ASA), ea., Multiple Cropping. Special Number 27, 3rd printing 1979, Madison, Wisconsin

Bennet, A., and Schork, W., Preliminary Research Towards a Sustainable Agriculture in Northern Chana - internal working paper on agro-ecosystems, unpublished manuscript, Heidelberg 1979

Bergmann, H., Agricultural Instruction in Primary Schools - A Contribution to Rural Development? in: Development and Cooperation No 2, 1978, p. 9-11

Bergmann, H., General Guidelines for School Agriculture, IPAR Buea 1977, cyclostyled

Cadillon, M., Evolution du Sol sous une Rotation Baoulee Traditionelle, IRAT, Bouake, undated

Cleave, J.H., African Farmers: Labour in the Development of Smallholder Agriculture, Praeger, New York, 1974

Egger, K, and Mayer, B.J., Agro-Technological Alternatives for Agriculture in the Usambara Mountains, Tanzania, Kubel-Stifung, Bensheim, 1979

Francis, C.A., Flor, C.A., Temple, S.R., Adapting Varieties for Intercropping Systems in the Tropics, in: ASA, Multiple Cropping, p. 235-253

Holway, J., Good-Bye to the Plough? How American Farmers Are Saving the Soil: in Development and Cooperation No 1, 1978, p. 16-17

Consultative Group on International Agricultural Research, International Research in Agriculture, New York 1974

Lagemann, J., Traditional African Farming Systems in Eastern Nigeria, Weltforum Verlag Munchen, 1977

Leakey, C.L.A., and Wills, J.B., Food Crops of the Lowland Tropics, Oxford University Press 1977

Litsinger, J.A., and Moody, K., Integrated Pest Management in Multiple Cropping Systems, in: Multiple Cropping, p. 293-308

Meuer, G., Eco-Farming in Practice - The Agro-Pastoral Project in Nyabisindu, Ruanda; Development and Cooperation, No 4/1977, p. 17-21

Ngende, F.E., Geography of West Cameroon, Victoria, 1966

Ngwa, J.A., An Outline Geography of the Federal Republic of Cameroon, London 1967

Obi, J.K, and Tuley, P., The Bush Fallow and Ley Farming in the Oil Palm Belt of South-East Nigeria, Foreign and Commonwealth Office, Overseas Development Administration, Miscellaneous Report 161, 1973

Oelsligle, D.D., McCollum, R.E., and Kang, B.T., Soil Fertility Management in Tropical Multiple Cropping, in: ASA, Multiple Cropping, p. 275-292

Okigbo, B.N., and Greenland, D.J., Multiple Cropping in Tropical Africa, in: ASA, Multiple Cropping, p. 63-101

Simon, H., WADA - A Programme of establishing a training centre for draught cattle, Wum, 1974, cyclostyled

Simon, H., Farming in the Tropical Highland of North-West Cameroon, unpublished manuscript, Bamenda 1978

Smith, R., Tree Crops - A Permanent Agriculture The Devin-Adair Company, Greenwich 1977

Smock, D., and Smock, A., Cultural and Political Aspects of Rural Transformation - A Case Study of Eastern Nigeria, New York and London, 1972

Tourte, R. and Moomaw, J.C., Traditional African Systems of Agriculture, in: Leakey, G., and Wills, J.B., Food Crops of the Lowland Tropics, p. 295-312

Trenbath, B.R., Plant Interactions in Mixed Crop Communities, in: ASA, Multiple Cropping, p. 129-163

Nwosu, N.A., Some Indigenous Cropping Systems of Eastern Nigeria, Umudike, Nigeria, undated
de Wilde, J.C., et al., Agricultural Development in Tropical Africa, vol. I, Baltimore, The John Hopkins Press, 1967

Part II: Crops

Assoumou, J. L'economie du Cacao, editions universitaires delarge, 1977

Bederman, Sanford, H., The Cameroons Development Corporation - Partner in National Growth, Bota 1968

Cameroon Development Corporation, Annual Report and Accounts for the 12 months ending 30th Juni, 1973, Bota, Victoria

Ejedepang-Koge, S.N., Tradition and Change in Peasant Activities - A Study of the Indigenous People's Search for Cash in the South West Province of Cameroon, Yaounde 1975

FAO-INADES, Coffee, Better Farming Series Nr. 23, Rome 1970

FAO-INADES Groundnuts, Better Farming Series Nr. 19, Rome 1970

FAO-INADES Upland Rice, Better Farming Series Nr. 20, Rome 1970

FAO-INADES, Wet Paddy or Swamp Rice, Better Farming Series, Nr. 21, Rome 1970

Ghanaian-German Agric. Development Project Northern and Upper Regions, Agricultural Extension Handbook, Eschborn 1977

IPAR-Yaounde, Geographie du Cameroun, Yaounde 1972

Irvine, F.R., West African Crops, London, Oxford University Press 1976

Kaberry, Phyllis M., Some Problems of Land Tenure in Nsaw, Southern Cameroons, Journal of African Administration

Kenya Institute of Education, Agriculture, Unit Three, Crop Husbandry - Teachers' and Students' Manual experimental version, Nairobi 1977

Leakey C.L.A., and Wills, J.B., Food Crops of the Lowland Tropics London: Oxford University Press 1977

Ministere de l'Education Nationale, Le Bananier Plantain, Bibliotheque du Maitre et des Eleves, vol 10 Yaounde 1974 same author Racines et Tubercules Bibliotheque du Maitre et des Eleves, vol. 3, Yaounde 1974

Mohr, B., Die Reiskultur in Westafrika - Verbreitung und Anbauformen, Munchen 1969

Mutsaers, H., Les Cereales et la Canne a Surcre, Universite de Yacounde, Ecole Nationale Superieure Agronomique de Nkolbisson, 1977

Ndenge, A.F., Science for Beginners, Victoria 1972

Phillips, T.A., An Agricultural Notebook, London 1972

Postgraduate Training Centre for Agricultural Development, Possibilities of the Introduction of Draught Animals in the North-West Province of the United Republic of Cameroon, Berlin 1978

Provincial Delegation for Agriculture, Technical Annual Reports of the North-West Province 1974/75 and 1976 Bamenda

Provincial Delegation for Agriculture, Annual Reports 1973/74; South-West Province, Buea Presbyterian Rural Training Centre, Annual Reports 1974, 1975, and 1977, Kumba Presbyterian Rural Training Centre, Kumba, Rice - A Short Introduction to the Cultivation of Wet Paddy, undated

Rashid, A., Economics of Rural Living in the Areas of Nso and Ndu, Bamenda 1974

Rehm, S., and Espig, G., Die Kulturpflanzen der Tropen und Subtropen - Anbau, wirtschaftliche Bedeutung, Verwertung, Stuttgart 1976

Rural Science Tutor, St. John's TTC, First Yam Production Experiment at St. John's College, Nchang 1966

Southern Cameroons Development Agency, Third Report of the Southern Cameroons Development Agency, April, 1959 - March 1960, Buea 1960

W.A.D.A. (Wum AreaDevelopment Authority), Annual Reports 1971/72, 1972/73

W.A.D.A., A programme of establishing a training centre for draught cattle in the Wum Area Development Authority, Wum 1975

W.A.D.A. Final Report of the outgoing director, 1975, Wum

W.A.D.A. Extension Section, Rice Cultivation, undated, Wum

West Cameroon Development Agency, Fifth, Seventh, Eighth, and Ninth Report, Buea, 1962, 1964, 1965, 1966

Westphal, E., Leguminous Crops (pulses), second revised edition, Ecole Nationale Superieure Agronomique, Nkolbisson 1977-78

Westphal, E., Root and Tuber Crops (second revised edition), E.N.S.A., 1978

Part III: Crop Storage

References contained within the text.