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close this bookAgroforestry in the West African Sahel (BOSTID, 1984)
View the document(introduction...)
View the documentAcknowledgements
View the documentPreface
View the documentOverview
View the documentChapter 1: Desertification in the Sahel
View the documentChapter 2: Traditional Land Use Systems
View the documentChapter 3: Uses and Potential of Agroforestry
View the documentChapter 4: Agroforestry Applications
View the documentChapter 5: Sahelian Agroforestry: Institutional Considerations
View the documentReferences
View the documentBibliography
Open this folder and view contentsAppendixes

Chapter 4: Agroforestry Applications

When applied to the traditional African smallholder, the term "farm management" refers to a mixture of crop diversification, crop rotation, and introduction (where adequate water and appropriate soils are available) of small vegetable gardens, fruit orchards, and forage production for locally owned livestock.

Since intense heat is a mayor constraint in Sahelian environmental management, shade trees are highly valued. Villagers frequently request trees that provide shade for the family compounds, for school buildings, or for the marketplace. Despite the need for good farmland to provide basic staple food crops, local farmers often are willing to set a few corners aside for trees. High on the list are fruit trees: mangoes, citrus, guavas, and papayas. Next come "food trees." Many local sauce and stew recipes call for substantial amounts of leaves from various local trees such as Adansonia digitata. Forage trees and shrubs are also highly desired.

Quite often, farmers do not interplant more of these useful trees only because seedlings are not available. While the introduction of plastic pots in nurseries has made it possible to produce planting stock of this kind, most forest services plant rapid-growth exotic species used in larger scale reforestation schemes and only recently have begun to promote local species.

As noted elsewhere in this report, trees can play several important roles if they are properly integrated into conservation-oriented farm practices. They produce shade, fruit, and other foods, but when integrated into soil-conservation activities such as the construction of berms and terraces, they can provide cover and protection against wind and can anchor water-control structures. They also improve the microclimate. Furthermore, leaves and other litter fall to the ground and resupply the soil with nutrients and organic matter. Well-selected trees and shrubs can contribute to soil conservation and improvement and the restoration of ecological balance and, at the same time, play an important role in providing food, fuel, fiber, pharmaceutical products, economic products such as gum and honey, and many other items that have disappeared because of advancing desertification.

Tree Crops

Many indigenous fruit and food trees play an important role in providing more balanced diets and/or additional farm income. In areas receiving more than 700 mm of rainfall, or along mares or depressions, two tree species are of particular interest: Butyrospermum paradoxum and Parkia clappertoniana. Both furnish important products that are used in even the most modest kitchen. Shea butter is produced from the former by a long and tedious process and provides fats and vegetable protein, which are inadequately supplied by standard cereal staples. The pods and seeds from P. clappertoniana are used as the base for such local sauces as soumbala which, like shea butter, provide proteins as well as vitamins and minerals otherwise missing from diets. A refreshing vitamin-rich drink is derived from the sticky pods of Tamarindus indica. The acid contained in these pods is mixed with local millet and sorghum gruel to make them more digestible. Moringa oleifera, very much appreciated for its edible leaves, is found in many local gardens. Ficus spp., Zizyphus spp., Balanites aegyptiaca (desert date), Borassus aethiopum, and other species similarly serve as important sources of food. These trees contribute so much to the basic diet and traditional well-being of Sahelian populations that they are considered valuable assets in farm fields as well as around compounds and villages, even if they compete to some extent with staple crops.

Natural regeneration of Acacia albida and other valuable species is declining in many places. Intensive farming "including weeding and land clearance by animal traction or tractors) no longer allows a farmer to weed around young seedlings. Animals in ever-increasing numbers browse on the young shoots and destroy what is left. However, all of these species have been successfully established in nurseries from seeds and transplanted into fields, and seedling supply need not be a problem.

The major issue in planting trees, then, is to find local people who are willing to take the extra steps necessary to plant and protect the seedlings during the first few years. After the harvest, animal owners allow their livestock to forage on the stalks and leaves of the previous season's crop. While it is not always possible to ask animal owners to keep their sheep, goats, cows, or donkeys away from newly planted trees, which may be scattered throughout the farm fields, it can and has been done in selected sites with considerable effort, supervision, and care.

Shelterbelts

Shelterbelts occupy a special place in agroforestry. Where wind and heat adversely affect farm yields, properly designed shelterbelts can increase production substantially. Net production increases of over 30 percent in protected fields have been reported in Niger (in the Bouza District windbreak project).

What began as an effort simply to establish a living barrier against winds, quickly developed into a multipurpose operation.

Properly managed, shelterbelts produce not only firewood, poles, and branches for fencing but also some fruit and forage. Further, as leaves fall from the trees, they are scattered across the fields, providing the soil with critical nutrients and substantial amounts of organic matter.

In certain regions, it has been found that although people are reluctant to set aside larger blocks of farmland for tree plantations, they are less opposed to taking a strip of land out of farm production to establish shelterbelts. Cooperation can be easily arranged because farmers are convinced that they increase crop yields, even after the land they occupy (around 10 percent) is taken into account. The reasons for this receptivity should be carefully documented so that cooperation in such efforts can take place elsewhere.

The current preferred approach to establishing a multipurpose shelterbelt is to have a mix of rapid-growth species for immediate protection; slower-growing trees that eventually grow quite tall, extending the wind-shielded area; and smaller trees or bushes that produce a variety of by-products (such as Acacia nilotica pods, which are in strong demand by local tanneries) and fill the air spaces closer to the ground.

For further information regarding the establishment of shelterbelts in the Sahel, see the National Research Council's report, Environmental Change in the West African Sahel (1983).

Contour Planting

The planting of valuable, multiple-use tree species in association with terraces, berms, and ditches in soil conservation projects allows socially beneficial production to be combined with much needed soil conservation measures in Sahelian farming systems.

Vegetation Strips

Horizontal vegetation strips consisting of bands of different trees and shrubs established along contour lines to prevent soil loss by erosion is another concept worth mentioning. These strips can eventually be rotated every 10 years so that an adjacent band is established while the previous belt is cleared and its restored and rejuvenated soils farmed again.

Trees and shrubs can also be used effectively to protect and stabilize slopes and banks along natural erosion channels or along runoff swales in farm areas.

RAINFED AGRICULTURAL PRODUCTION

Among the numerous factors that limit crop production under rainfed conditions in the Sahel, two are of overriding importance: (1) the efficiency with which crops and range vegetation use available moisture, and (2) soil fertility and the availability of critical plant nutrients. These two factors are intimately interrelated.

In many traditional systems, crop production, soil fertility, and soil structure (an important determinant in the capacity of the soil to hold and supply water) were maintained by extended fallow periods between shorter cropping cycles. During this fallow period, native plant species--predominantly deep-rooted, woody leguminous species--became reestablished and provided ground cover essentially equal to that provided by the natural vegetation before the land was cultivated.

Under alternating cycles of 3-4 years of cultivation and 15-20 or more years of fallow, soil fertility and structure, including organic matter content, were maintained with virtually no deterioration over time. Soil fertility was maintained through the recycling of mineral nutrients by trees and shrubs with deep root systems extending beyond the leached surface horizons, and through biological nitrogen fixation by soil microorganisms such as Rhizobium spp. and various free-living, nitrogen-fixing bacteria and blue-green algae. Soil structure was maintained by the combined action of the deep and extensive root systems of the trees and shrubs and by leaf fall. The enhancement of capacity to absorb water contributed to the maintenance of soil moisture at capacity levels, thus controlling runoff and thereby reducing erosion.

As the intensity of land use has increased with population growth, the long fallow period has been reduced. In some cases, the fallow period has been so reduced that few trees and shrubs survive to become reestablished and make sufficient growth to be useful. The vegetation that develops during the short fallow period is dominated by shallow-rooted grass species that contribute little to regeneration of soil fertility and structure. The recycling of nutrient elements and nitrogen fixation essentially stops. The infiltration of water into the soil is reduced, thus increasing runoff and erosion. Reduced ground cover further facilitates wind erosion. Although there are few reliable data to confirm this, it appears that the productivity of Sahelian soils has declined under more intensive cultivation.

Investigations by the Institut de Recherches Agronomiques Tropicales et des Cultures Vivrieres (IRAT) in Senegal and Upper Volta have demonstrated that the adverse impacts of the intensive use of Sahelian soils can be counteracted by the use of a variety of management practices. The use of heavy applications of manure or crop residues, applications of chemical fertilizer, and subsequent deep plowing were found to maintain and even increase productivity under conditions of continuous cropping with grain crops for periods of up to 20 years.

Unfortunately, these results have found little application. They are usually beyond the capabilities of Sahelian farmers, who have little manure, use crop residues for animal feed and other uses rather than for soil improvement, have little physical or economic access to chemical fertilizers, and are usually unable to practice deep plowing because they lack equipment and because the labor requirements are difficult to meet as most workers are engaged in the harvest and other activities such as crop transport and storage. Moreover, maximum effectiveness is achieved only if all practices are combined. The use of chemical fertilizers alone, for example, does not provide as good a response as when used in combination with the other practices.

The IRAT work, while demonstrating a technical methodology for maintaining productivity under continuous cropping, has not produced a practical solution or method for applying the technical solutions within the constraints under which most Sahelian farmers work. The challenge to researchers now is to develop practical methods for applying these technical solutions. It is within this context that agroforestry might best contribute to agricultural production in the Sahel.

The following comments relate only to the use of agroforestry plant species in combination with crop production for maintaining or enhancing productivity.

The principal objective of the farmer in the Sahel is the production of his basic food needs--grain and legume seeds. Any practice that interferes with achieving this objective is not likely to be accepted. Moreover, the precariousness of survival in the Sahel is such that the promise of better production, that is, better living in future years, is not sufficient incentive to ensure acceptance of a practice if doing so increases the risk of failure in satisfying current basic needs, or if it diverts meager resources, especially labor, from the task of producing basic food requirements. These conditions impose very definite limits on options for incorporating productivity maintenance or improvement schemes in the Sahelian rainfed agricultural production system. Hence, perhaps one of the principal advantages of agroforestry in the Sahel is that it is functionally and conceptually related to traditional agricultural systems in the region, and its implementation can therefore be supported by existing knowledge and techniques. In this context, agroforestry can be seen as an effort to strengthen and further diversify existing Sahelian systems.

A wide range of options has been suggested for the incorporation of agroforestry elements in agricultural production, including:

1. Various forms of intercropping and mulching

a. Intercropping with food crops
b. Intercropping with fodder species
c. Intercropping with browse species
d. Intercropping with multiple-use species (food, forage, fuel, construction materials, etc.)
e. Strip cropping with any of the above-mentioned types of crops
f. Use of mulch carried to cultivated fields from essentially non arable areas.

2. Use of leguminous plant species in a managed fallow system alternating with crops (strip cropping is a special example of this).

Studies to date have focused almost exclusively on the several intercropping options and variations of these. Although many species--mostly leguminous--have been mentioned in connection with intercropping, few have been studied to any degree, with the exception of the generally herbaceous food-producing species and a few woody species of genera such as Leucaena, Gliricidia, Prosopis, and Acacia. Very little has been done, or even suggested, to develop managed fallow systems that would simulate the traditional natural fallow system in terms of its capacity to restore soil fertility.

The study and development of managed fallow systems seem to offer some promise, particularly if certain prerequisite conditions can be met: (l) the system and species used must have utility other than that of soil improvement (for example, food, feed, construction, fuel); (2) the system must not compete for labor during the peak period of labor demand by the food-producing systems; (3) it must be capable of producing useful soil regenerating effects in a relatively short period (2-4 years); (4) it must not require a substantial outlay of capital; and (5) the system must be manageable (that is, the species used must be easily established). Furthermore, the species used must be capable of rapid early growth to reduce weed competition; they must not become weeds themselves or harbor insects, disease, or bird pests; and they must be easily destroyed in order to return the land to cultivation.

To date, the systematic evaluation of species, both native and exotic, for potential use either in the intercropping or the managed fallow systems has not been undertaken. A thorough understanding of the behavior of the different species under a few carefully selected conditions would greatly facilitate the conceptualization of potentially useful systems that could be tested in a wide range of environmental conditions. The time spent in such a systematic study of species would probably be more than compensated for by reducing the trial-and-error nature of the ad hoc studies carried out to date.

FORESTRY AS A COMPLEMENT TO SAHELIAN AGROFORESTRY

Much can be done in the forestry sector both to support agricultural production and to better assure environmental diversity. The Sahel, as mentioned earlier, is not forest land, and many discussions about forestry in the Sahel actually refer to the better-watered savanna zone. Forestry as a land use system in which trees dominate and in which artificial or natural regeneration, silvicultural treatment, and rational wood or multiple use are practiced will have to be studied in order to find a system appropriate for the Sahel. Given the generally harsh conditions, this will not be easy.

"Traditional" forestry can, however, serve the following roles:

1. Protective functions resulting in improved quantity or quality of production within the context of an integrated multiple land use system

a. Improvement of the microclimate at the site b. Regulation of the water regime
c. Preservation, restoration, and improvement of the soil
d. Protection of land in use (cropland, pastures, settlements, water basins, roads)
e. Preservation of plant and animal species, protection of wildlife.

2. Productive functions as a supplement to animal husbandry and dryland farming; that is, production of:

a. Wood as an energy source (firewood,charcoal)
b. Wood as a building material
c. Fruits, food, and leaves as food and fodder
d. Additional forest products for commercial use and export, such as gum arable, tannin, and fibers.

3. Protective and productive functions that lead to social benefits

a. Improved supply of goods to satisfy daily need; creation of reserves for periods of drought or other emergencies
b. Activation of resources for economic development
c. Creation of Jobs, with special consideration of spatial and temporal concentrations.

Although trees and shrubs have always played an important role in the lives of Sahelian people, the potential of these woody plants has not yet been fully developed. Hence, the forester's responsibilities in the Sahel ideally would be to maintain the existing woody vegetation, to establish and maintain new local and exotic trees, and to improve their productive and protective functions which help prevent desertification, solve household energy problems, and thereby contribute to the stabilization of human societies and environmental systems.

WHAT CAN BE DONE?

There are three different levels at which action can be taken: governments, communities, and individual households.

Action by Governments

Governments, represented by their forest services and sometimes supported by international assistance, are trying to protect and preserve valuable natural forest resources, carry out inventories, and improve woodland management. Forest plantations should be established on government land in the vicinity of population centers or markets, preferably with one or several fast-growing species, yielding firewood and utility timber. Afforestation costs are high (between US $500 and $1,000 per hectare) and yields are low (rarely over 2 m3/ha/yr)--a very expensive undertaking while funds are extremely scarce (Keita 1981). Regarding the magnitude of demand, afforestation can only solve very specific problems on a small, local scale. In addition, there is a very serious shortage of technically trained manpower. Although locally available manpower should be substituted for mechanization insofar as possible, this proves difficult in large-scale afforestation efforts in the Sahel because basic work like clearing operations and soil work (deep-digging, breaking up heavy or stony soil such as lateritic soils, and subsoiling) may require heavy equipment. Also, the bulk of establishment and maintenance work falls within the rainy season (from June to the end of September), and it is almost impossible to mobilize people for forest work when food production has priority and, in fact, requires the presence of every able-bodied member of the family in the fields. Thus, forestry is facing not only a shortage of funds but, more seriously, competition for manpower and, of course, competition for suitable land.

In addition to preventing forest destruction--for example, by uncontrolled bush fires or illegal felling--the forest services at the outset should concentrate on the establishment or improvement of local nurseries to supply tree seedlings of high quality for village tree planting at the proper time. Forest services should also function as advisors to rural communities and individual tree planters to promote private activities instead of acting mainly as forest police or collecting taxes for what were formerly free uses of forest products.

Forest services should, moreover, promote agroforestry by opening their plantations for private interplanting of agricultural crops. Even controlled grazing or cutting of grass for livestock would be of mutual benefit and would make people understand the usefulness of forestry operations. The current practice of fencing plantation perimeters, keeping people out, and penalizing those who enter creates hostility instead of willingness to cooperate. Agroforestry, however, could facilitate dialogue with rural people, may prove to be of high educational value, and may help to improve the forester's revenues and reputation at an early stage.

Action by Communities

Forestry at the community level is most easily introduced in societies that have a strong traditional structure and are accustomed to neighborhood cooperation and Joint efforts in land management. The leaders of these communities, or the speakers for local development councils, will help to identify the products that people need from the forest. They can arrange for suitable land to be demarcated for tree planting, and for the proper timing of forestry and farmwork.

Village forestry has great promise in the Sahel. The most obvious application is for shade trees to be planted in the village in public squares such as the market, and in front of public buildings such as offices, mosques, and schools, and alongside roads. There quite often will be a demand for a community tree nursery (if not already available from the forest service) to supply shade and fruit or food trees. Step-by-step extension work can gain cooperation, leading ultimately to community-owned forest tree or shrub plantations that provide firewood, poles, fodder, and various other forest products and that also have protective functions by serving as windbreaks, providing erosion control, and contributing to sand-dune fixation.

Action by Households

Quite often it will prove more effective to cooperate with individual progressive farmers than with an entire community or with a farmers' cooperative. Occasionally, farmers who are willing to cooperate may be very selective, because they may have had bad experiences with government or international projects or because they know better than their advisors how to satisfy their specific needs, how to consider site differences, the utility of tree and shrub species, and the risks of planting. Farmers will plant and protect trees if they can expect the initial benefits from them within 1-4 years, if the full right to dispose of their trees rests untouched by official supervisors (and the forest law), and if growing trees is compatible in time and space with their traditional land use patterns.

FERLO MODEL: A CASE STUDY

An agroforestry land use model has been developed in the Ferlo Region in northern Senegal to meet people's demands and to combat desertification by increasing the carrying capacity of the region. The Ferlo is rangeland with annual rainfall between 150 and 350 mm in the northern zone and between 350 and 550 mm in the south. Soils are mainly loamy sands with local variations. Nomadic and transhumant herders (Fulbe, Tokolor, and Moors) in the north and sedentary farmers (Wolof) in the south make up the mayor part of the population.

In 1975 a German-Senegalese forestry project was initiated to:

. Develop an agro-silvo-pastoral land use system adapted to local needs where all measures preventing desertification and securing sustained yield should be combined. The local peasant population was to be involved in tree-planting projects as part of a self-help program.
. Aid in restoring the seriously endangered vegetation around six deep-well sites.
. Create guidelines for the permanent settlement of people in numbers proportional to the ecological carrying capacity of the environment.
. Increase the production of gum arable, fodder, food, and wood.
. Improve regional protection against bush fires.
. Improve the efficiency of the Forest Service.
. Create jobs and opportunities for cash income.
. Prevent catastrophes and gain experience in effective regional development under Sahelian conditions.

The strategy for achieving these objectives was relatively simple. As the region is heavily degraded, initial emphasis was placed on the identification of critical centers of degradation, such as well sites. Remedial measures were then undertaken radially from these centers with diminishing intensity. The strategy relates well to the environmental needs of the region, as well as to the socioeconomic requirements of the semi sedentary population (see Figure 6).

A plot of suitable land was identified by local village authorities (ideal size is 100 ha, although smaller plots may be chosen). This area was allocated to individual families, about 5 ha per family. These families were given sole responsibility for management of the land and will also be the only beneficiaries. All clearing operations were carried out in the traditional manner with local tools during the dry season. Thereafter, as part of "technical" assistance, cross subsoiling was done with a tractor or Unimog, working to a depth of 40-70 cm. (Cross-subsoiling helps keep the moisture from rainfall available to plants for a much longer time than with other techniques.) In addition, the plot was temporarily fenced with barbed wire, where necessary. All of these operations required an investment of US $50 to $250 per hectare from project funds.

Since 1975 the project has developed from a Forest Service enterprise to an integrated rural development program with active village participation. Recent development has focused on farm or community forest activities on private farmland. Though simple, the model is very flexible.

The farmers now plant Acacia senegal or other useful tree seedlings using 10 x 10 meter spacing and at the same time plant traditional crops between the trees. They grow millet, groundnuts, and cow peas during the rainy season for 3 years; weeding is done simultaneously for crop plants and trees. According to available information, overall yields are impressively higher than those of traditional fields. Whether this is due to deep subsoiling, careful protection of the land against animals and bush fires, or the ameliorative effects (shade, wind control, nitrogen fixation) of the trees, or because of all three, remains to be investigated in detail. After 2 years of fallow the natural grass vegetation will recover and surpass biomass production of adjacent pastures. This process can be further improved by sowing selected fodder grasses. Grass eventually has to be cut to avoid competition with the young trees, but it can be sold at the well center, where thousands of head of livestock assemble daily during the dry season.

When the trees are about 5 years old, sheep, and to some extent, cattle and even goats can be admitted to the plantation. It appears that l sheep/ha/yr can be fed without doing harm to the trees. The Acacia senegal trees yield gum arabic over a period of 15 years. Gum arabic is a traditional and profitable product of the region; its price is guaranteed by the government. Twenty years after establishment the trees will be felled for firewood and poles, and the cycle will be started again.


FIGURE 6 Plan of land use in the area surrounding the well sites.
(1) Center of development (deep well, village): water supply through deep well, administration buildings, residence area, marketplace, shops, workshops; small plots with trickle irrigation for home gardens and vegetable production.
(2) Inner land use zone: (a) agroforestry plots of some 100 ha each to be managed by about 20 family units; (b) intensive range management of fenced grasslands, with high percentage of tree and shrub cover.
(3) Outer land use zone: (c) forest plantations (e.g., with Acacia senegal and, if applicable, with intermediate rainfed agriculture or controlled grazing), production of gum arable, firewood, poles, etc.; (d) protected areas (eventually fenced or with firebreaks) for natural regeneration of local species. All other areas are left to traditional land use. (Source: H.-J. von Maydell)

This system is flexible in that the trees and their products and the crops can be used, and because it meets a variety of basic local needs. It is, moreover, fully acceptable to the people and makes them less dependent on outside assistance. As proof of the project's popular acceptance, more than 20 villages with over 1,000 families had voluntarily joined the program within 2 years of its initiation, and all participants say they are much better off than before. The Senegalese government has used the same guidelines for a large-scale project in the adjoining region to the west, and the European Community Development Fund (FED) will sponsor a similar project to the east.

This system involves increased responsibility on the part of program planners and managers and the scientists who must ensure that the system follows the overriding principle that every product, every function and organization of land use must be compatible with the sustained productivity of the human and natural ecosystems. Meeting this responsibility in turn demands that a considerable amount of interdisciplinary applied research be undertaken. In every project, each farm or village forms a system of many components with close interactions; therefore, isolated activities may severely disturb the whole project or, at a minimum, have desirable or undesirable effects on the other components. Consequently, applied research in support of agroforestry land use development is considered an integral part of and a precondition for success. Such research might include observations made by farmers and herders as well as desk and laboratory work in expatriate institutions and should always be correlated with practical fieldwork and local needs.

EVALUATION

It is generally accepted that evaluation is needed at each step of a development process. Determining what constitutes "evaluation," however, is often more complicated than one might suppose. The simplest criterion would be to ask "Does it pay?" Of course, basic rural development goes far beyond monetary considerations. A farmer who was asked what he thought about the changes that took place after he Joined the agroforestry program said: "I am satisfied in my heart." A governor, asked how he evaluated agroforestry in his region, replied: "People, under stress, used to be aggressive and destructive. They are now cooperative. This is the change we welcome." How should such statements be converted into monetary terms? How should conservation of endangered species, of natural resources, and reduction of risks in land use or achievements in making people aware of their responsibility for their country be valued?

Other sectors are more easily quantified and qualified for evaluation purposes. Monitoring of sites, crops, social changes, and so forth, plays an important role in this context; so do trend analyses and interpretations. In principle, evaluation of project impact requires that an inventory be made at the time of project initiation to define a baseline for future comparison. Evaluation of the project should then quantify and qualify changes in the natural and social environments. The human aspect is particularly likely to be difficult to assess because of subjective responses to change. There will be positive records: firewood production increased tenfold; grass production increased threefold; 1,000 ha of moving sands were stabilized and converted to silvo-pastoral cropland. Agroforestry land use systems, in the long run, will be judged against two criteria: (1) the persistence and (2) the resilience of the agroforestry scheme under Sahelian conditions. Persistence refers to the ability of the system to remain as it is, despite environmental and human influences. High persistence means small variations and high resistance to destruction. Resilience refers to the probability of quantitative and qualitative changes, that is, response by adaptation. An ecosystem with high resilience, when disturbed, accommodates high-amplitude variation, but it returns to its former structure as soon as the disturbance subsides.

Sahelian ecosystems are subject to high-amplitude change and are very flexible in terms of ecosystemic response to these changes. Both persistence and resilience are needed to survive in the Sahel. Agroforestry, properly applied, offers a wide range of techniques, species, and strategies to enable Sahelians to meet their basic needs.