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close this bookSPORE Bulletin of the CTA No. 14 (CTA Spore, 1988, 16 p.)
close this folderGrowing vegetables and hope
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View the documentAgroforestry farming with trees


Until recently, most market gardens were located on the outskirts of cities and, in a few cases, even within. They have now spread to rural areas but their viability there is threatened if transportation and marketing systems are not improved. If rural producers are to succeed, both agronomic and economic solutions to their problems need to be found.

The success of market gardens depends primarily on the initiative of these new entrepreneurs, whose numbers have increased dramatically over the last few years. Different production systems and objectives, as well as varying results, combine to make generalizations difficult in this field. It can be said, however, that if vegetable production in cities is designed to satisfy the large demand of consumers, in rural areas it reflects primarily the objectives of the producers themselves.

Market gardeners have flourished in African cities because their crops can produce large quantities from small areas. Using sewage sludge to enrich their compost and grey or used water for watering, such gardeners often exploit any available land, even in the centre of urban areas. Increasing construction in urban areas, however, is slowly pushing them out to suburban plots or land even further away from the city. Even so, many market gardeners are still producing on small plots ranging in size from less than ten to up to 100 square metres which are intensively cultivated by hand. In Kinshasa, more than 6000 urban farmers were identified in the business of supplying both the city and surrounding towns.

Such producers are very diverse: they include women seeking financial independence; civil servants who want to supplement their incomes; young people who are attracted by such "modern" agriculture; and the unemployed.

Increasingly, however, it is men who make their full-time living out of market gardening because it can be very lucrative. They specialize in European type vegetables (potatoes, cabbage, tomatoes, carrots, squash, and so on) leaving their wives the responsibility of growing African vegetables. But despite the spectacular growth of market gardening in urban and suburban areas the supply of cities generally remains inadequate. In Brazzaville, of the 18,000 t of vegetables consumed annually, only 3000 t are produced locally. Projects like Agricongo are attempting to modernize and increase production around urban centres.

Families in rural areas have always grown their own "sauce ingredients". These consist of various local crops (okra, pimento, tomato, leafy vegetables) produced in small backyard plots, or in association with other food crops in more humid areas. What is new is the appearance in the countryside of market gardens whose produce is destined to be sold elsewhere. The revenue from such sales is generally used to buy cereals thereby ensuring local food security. By improving living conditions in rural areas, NGOs and some governments also hope to limit emigration towards the cities (see SPORE No. 2). Market gardening is also well received by local farmers because it does not compete with their cereal crops, which remain the first priority. Produced during the off-season, vegetable crops can be used to exploit both idle hands and abandoned lands. Furthermore, although they require intensive care, there is no need for expensive equipment or specialized techniques to succeed.

Such initiatives have been rapidly developed not only in the droughtstricken Sahel but also in more humid regions where they can generate considerable revenues. One indication of this is the considerable amount of land now dedicated to market gardening. Collective gardens have sprung up around wells and vegetables now occupy increasing space in irrigated fields. Lands that were abandoned, such as easily-irrigated lowlands or sandy soils unsuitable for cereals, have now been brought back into production. Growing methods have also changed: cultivation is now more intensive, green manure is being used, and improved seeds are being introduced.

Enthusiasm but little experience

For the first few years, the enthusiasm of farmers and some NGOs disguised the problems inherent to this kind of production. The multiplication of these projects throughout sub-Saharan Africa also tended to ignore the fact that to succeed, crops must not only grow well but sell well. Unfortunately, very little was done in the beginning to ensure production and commercialization of such cross.

One of the main difficulties is that there is no regular supply of inputs. From time to time it is difficult to get the right seeds as improved varieties for foreign vegetables are rarely produced locally. Imports are either insufficient or arrive too late, especially in remote areas. Furthermore, there is the problem of hybrid seeds that cannot be reproduced at all and must be bought every year.

This is particularly crucial for potatoes, an up-and-coming new crop. Local production of seed potatoes is often impossible because the tubers are difficult to store under tropical conditions. They are supplied from Europe but often arrive too late. The organization of seed production is one of the main priorities in order to increase the output of market gardens. Furthermore, the plants themselves are not always adapted to the local climate or cultivation techniques. Improved varieties are more sensitive to drought and pests. Finally, it is unfortunate that so little work has been done on local vegetables that are more resistant and which can be grown during the hot and humid season.

Such crops require more stringent protection measures, all the more important because they grow during the dry season and thus are a prime target for insects that have nothing else to eat at that time. That explains why cotton pests such as Heliothis become major problems for out-ofseason tomatoes, why thrips attack onions, or diamond-back moths threaten cabbages. To limit such damage, growers treat their beds with insecticides which they find on the local market, often designed to be used on cotton crops. Unfortunately, they are poorly trained in the use of pesticides and have little choice other than, as one of them explained, the "white powder bought in bulk at the market". Excessive treatments are common especially in suburban areas. This leaves toxic residues on the produce and builds up resistance in the pest themselves.

The growers also have to deal with other, more dreaded problems such as nematodes or Pseudomonas solanacearum, a bacterium that infects the soil and makes it unfit for growing tomato crops. Researchers are now working on improved varieties to help overcome such difficulties.

Plant problems are particularly serious in humid, tropical zones with relatively little direct sunlight. On the other hand, tropical uplands which have lower temperatures are much more suited to producing a large variety of vegetables. If such regions are well exploited, it seems that they could supply large areas. Generally speaking, research on market garden crops remains inadequate. Current work deals with the selection of new varieties and crop protection. In view of the increasing importance of such crops, however, national and foreign research organizations are renewing their interest in these long-forgotten crone.

Commercialization is lacking

The sale of market garden produce essentially takes place through the traditional systems which usually rely on women. These networks involve numerous intermediaries, except for the very small producers who sell directly on the local markets. Transportation systems that are often inadequate or poorly adapted, and poor packaging and storage methods, result in heavy losses. Furthermore, those producers who are far removed from markets depend entirely on local merchants for information about current prices and supply conditions on the market. Those who are not near major transportation routes or urban areas are faced with considerable problems in selling their produce. Sacks of onions and crates of tomatoes often rot by the roadside because of poor collection and transportation systems.

Another problem is that many of these vegetables mature at the same time. In the Sahel, they all arrive at the same time on both rural and urban markets, usually between January and March. Sales during such periods of glut are often impossible and the bottom can fall out of the market. This has happened much more frequently during the last few years with the increase in the area cultivated. Villagers outside Matam in the Senegal River valley, for example, are no longer able to sell their produce on the saturated local markets

For farmers, sales are often the only reason for growing such crops. If they cannot make sufficient profit this way, they prefer to find a more lucrative activity that requires less effort. With the good results of the past few years, their financial needs are less pressing. In some areas there has already been a movement away from market gardening towards other activities that are considered to be more profitable such as gold panning or jobs in the city.

The question that remains is how to increase sales. Several answers are possible but there are no easy solutions. An increase in the consumption of vegetables in rural areas is encouraged, primarily to improve the local diet, which is often inadequate. The consumption of fresh vegetables in rural areas is far behind that in urban areas and European vegetables are eaten only as a last resort. In Mauritania, for example, the average annual consumption of vegetables is about 24 kg but villagers eat only 6 kg. Modification of traditional eating habits is necessary.

Spreading out the production period is another way of ensuring better sales. This could involve the development of tomato varieties that grow during the winter and others that can be planted early. African vegetables that can be grown throughout the year also enable farmers to spread out their production

In order to ensure more regular supply for markets, attention must also be given to better storage methods. In this respect, onions and potatoes are receiving research attention designed to find varieties that keep better. For highly perishable produce, such as tomatoes, processing techniques are recommended. Solar drying is a simple solution available to all but it alone cannot handle large excesses. The development of small industrial units to process tomatoes into concentrate seems promising but, in order to make such investments cost-effective, there needs to be good organization of production and collection systems.

At one point, export crops were hailed as the way of the future and this resulted in the development of numerous plantations outside urban areas. Markets for such products however, became more and more difficult to find and maintain. Today only green wax beans still find sufficient buyers. Produced in Senegal and Burkina Faso, they demand careful cultivation and harvesting, thus farmers have little room for error. Furthermore, shipping methods often require production dates that simply cannot be respected.

At the moment, the absence of guaranteed markets is the biggest obstacle to the success of market gardening. Efforts must therefore be made to give these crops the place they deserve in the local diet and economy of rural regions. It would be unfortunate if the enthusiasm of the farmers is not matched by equally energetic efforts of others to ensure that such hopes for the future are realized


3rd Seminar of CIRAD/DSA on ~Amenagements hydro-agricoles et systemes de production'. Montpellier. December 1986

Dupriez H and P. de Leener 1987 African Gardens and Orchards. Terres et Vie Wade, I., 1986 City Food: Crop Selection in Third World Cities. 54 pp

Available at USD 5 from: Urban Resource Systems 783 Buena Vista West San Francisco, CA 941 17


Agroforestry farming with trees

Agroforestry is a term which has only recently come into general use. It is used - and practised - most widely in tropical countries because of its advantages in optimizing production while reducing soil erosion. While the name may be new, the technique has long been practised in some countries.

A groforestry covers all systems where trees are deliberately left or planted on land where crops are grown or animals grazed, and so includes pratices as diverse as shifting cultivation, taungya, the growing of shade trees in cash crops such as coffee, and the use of living fences to contain or exclude animals.

The upsurge of interest in these practices over the last ten years stems from the increasing population pressures and shortages of food and fuel among poor people in many developing countries. To meet their needs, those living in the more marginal areas have been forced to shorten the time the land is left fallow, to encroach further into forested land, and to overgraze pasture. As a result, the natural soil cover has been removed and the recycling of nutrients prevented leading to soil erosion and rapid decline in crop yields.

Agroforestry is seen as one way of solving these problems, since by including trees in their farming systems, farmers not only benefit from a supply of wood and other tree products but help ensure their land remains fertile and productive as well

Leaf litter from the trees adds organic matter to the soil and acts as a mulch to retain soil moisture and prevent soil erosion. Deep-rooted trees may tap sources of nutrients which are out of the reach of annual crops, making them available once the leaves fall. Leguminous trees such as leucaena can also improve soil fertility more directly by nitrogen fixation. Tree roots can help bind the soil and also create channels which improve its aeration and permeability to water.

A mixture of tree and annual crops of different heights provides a more complete ground cover which again helps protect the soil from erosion and makes maximum use of available sunlight. The tree cover helps moderate extremes of temperature preventing rapid heat loss from the soil at night and protecting crops from excessive heat during the day.

While these environmental benefits are of great importance to the conservation of fragile ecosystems in the long term, farmers are more likely to appreciate the value of trees in their farming system if they can see more immediate rewards. Multi-purpose trees which provide fodder for stock and edible fruits or nuts, as well as fuel, timber and support for climbing vegetables are those most likely to be used.

Traditional systems

Traditional agroforestry systems differ in the extent of the association between tree and crop or livestock components. Amongst the most closely integrated agroforestry systems are home gardens such as those commonly found in West Java and the more humid parts of West Africa. These gardens contain an intensive mix of crops of all types so that their structure resembles the natural forest. Annuals such as rice, maize and sweet potato are among perennials such as fruit, nuts and fibres and forest trees retained to provide fuel, timber, tannins, gums and medicinal products. Fodder for small stock comes from tree leaves and the grasses which grow under the trees.

In the agroforestry system known as taungya, crops are grown among young trees only until the tree canopy closes over (one to three years), so that in this case the tree-crop association is temporary. The system was developed in Burma in the 1 850s, when foresters needed labour to help establish new plantations as teak was felled. By allowing farmers to grow crops among the trees, weed growth was controlled among crop plants and trees.

This system has since spread through Asia to Africa and Latin America. In West Africa it has been used to help establish plantations of Gmelina arborea. But although the system benefits poorer farmers as well as the forester, farmers sometimes resent the restrictions imposed and the constant need to move on. As a result they have been known to damage the trees deliberately and so postpone the time when they shade out the crone.

In the case of shifting cultivation, or bush fallow, trees and crops occupy the same ground in turn. Although the more valued trees may be retained during the years when crops are being grown, and the trees are never completely cleared, the association between trees and annual crops is less close than it is in other agroforestry systems. Even so in the past it shared many of the advantages of more closely integrated systems.

It is only now, when increasing demands o the land have led to shorter and shorter fallow periods, and in some cases eliminated them altogether, that soil erosion and reduced fertility have become a serious problem. Because bush fallow is the dominant form of farming in Africa as well as parts of the Pacific, it is this more than anything else which has promoted the search for alternative and more sustainable agroforestry systems.

For those involved in improving and developing existing systems, agroforestry demands an all-round approach very different from that found among conventionally-trained agriculturalists and foresters, so justifying the need for a new discipline with a new name. Researchers, extension workers, and policy makers concerned with agroforestry have to consider not only how these improvements will affect the sustainability of the system: they also have to take account of local laws and customs concerning the ownership of trees and land, since, for example, farmers may be reluctant to plant trees if this calls into question their rights to crop a particular area.

Although agriculturists can provide information about many of the crops found in agroforestry systems, little is known about most of the trees, with the exception of those such as leucaena, some acacias, glyricidia and calliandra. Even less is know about interaction between the trees and the crop. The research possibilities seem limitless.

Diagnosis and design

The International Centre for Research in Agroforestry (ICRAF) has played a key role in developing new research approaches to cope with the complexity of the subject. Established as recently as 1978, and based in Nairobi, its main aims are to initiate, promote and support research, and to increase awareness of the benefits which agroforestry brings. With only a limited number of staff, it is fulfilling these aims admirably, acting as a catalyst for agroforestry research worldwide.

To help researchers investigate existing systems, see how they can be improved, and set priorities for research, ICRAF has developed an approach it calls D & D - diagnosis and design. In the diagnosis stage researchers discuss with farmers their basic needs, such as those for food, fuel, shelter and a cash income. They examine the existing system in terms of both its productivity and sustainability. In the design stage they use their knowledge of agroforestry systems elsewhere to suggest improvements which the farmers might adopt straight away.

At the same time they identify more serious problems which might be resolved by research and the development of new technology.

ICRAF has also proposed that an agroforestry research network for Africa (AFRENA) be set up, linking researchers in five widely occurring agro-ecological zones, so that those with common problems can share information. Two such networks have so far been established. One links Malawi, Tanzania, Zambia and Zimbabwe which all have highland areas characterised by a hot or warm climate and a single rainy season, where the natural vegetation is miombo or savanna woodland. The second is in the hot humid lowlands of West Africa and initially involves only Cameroon.

ICRAF is supporting the programme by first promoting the network approach among government departments and research institutions in the countries concerned and then offering training in appropriate research methods. The networks should help researchers establish which problems are best solved on a regional basis and which should be tackled at the local level.

However ICRAF is by no means the only international centre concerned with agroforestry. The International Institute of Tropical Agriculture (IITA) based in Nigeria and the International Livestock Centre for Africa (ILCA) based in Ethiopia, and with an outstation in Nigeria, have for some years been testing and developing the agroforestry system known as alley cropping.

Alley cropping

Originally from Asia, this is one of the innovative approaches adopted to tackle the problems caused by reduced bush fallows. Food crops are grown in the alleys between the lines of trees or shrubs. The trees are cut back like a hedge while the crop is grown, but allowed to grow out and cover the soil once it is harvested. The benefits are similar to those in a traditional bush fallow, but in this case cropping and fallowing occur side by side, so allowing continuous use of the same piece of land.

The researchers have confirmed that alley cropping can be adapted to Nigerian conditions, and have tested several tree species, examining how they can be established, at what height they should be pruned, and the best distance between rows. The system has now been adopted by several villages in southwest Nigeria, although researchers were horrified to discover farmers growing highly competitive crops such as yam, melon and cassava between the young trees instead of the recommended maize. However, the trees survived and the researchers realised that what mattered was that the trees could be adapted to suit the farmers' existing system, not whether they took six months or two years to establish.

This example highlights the importance of considering the farmers' needs in order to simplify the research that needs to be done. Once it is established that a system works, and has advantages over the existing one, it is more appropriate to consider the range of conditions which component species can tolerate rather than under what conditions they grow best. For farmers with limited resources farming under highly variable conditions, it is the flexibility and diversity of traditional agroforestry systems which give them their strength.


Steppler, H A and P K R NAIR 1987 Agroforestry a Decade of Development ICRAF. Nairobi

Beets W. 1986 The Potential Pole of Agroforestry in ACP States. A State-of-the-Art Study. CTA. Wageningen

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