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Current agro-forestry activities

The integration of livestock production in agro-forestry
Intercropping of terminalia superba with cocoa and banana in mayombe, people's republic of the Congo
An example of agro-forestry for tropical mountain areas
Intercropping tree and field crops
Promising trees for agro-forestry in southern Nigeria
Food crop yield under teak and cassia siamea in south-western Nigeria
Agro-forestry possibilities in oil palm plantations in the Ivory coast
Effect of food crops on tree growth in Tanzania
Selection of leguminous trees for agro-forestry in Cameroon
Forestry aspects of agro-forestry practice in Nigeria
Summary of discussion: Current agro-forestry activities

The integration of livestock production in agro-forestry

J. Lazier, A. Getahun, and M. Velez
Small Ruminant Programme, International Livestock Centre for Africa, and International Institute of Tropical Agriculture, Ibadan, Nigeria

Abstract

West African Dwarf sheep and goats appear to have the potential to satisfy the increasing demand for animal protein in the humid zones of West Africa. Their current management is described, and their integration - together with that of cattle-into agro-forestry systems is discussed. The planting of browse species such as Gliricidia septum and Leucaena leucocephala may overcome the constraint to animal production caused by the lack of fodder in the dry season. Grazing in forests, plantations, and alley cropping systems is also discussed.

Introduction

The population of the countries of the humid zone of the west coast of Africa is about 160 million and is growing by more than 2.5 per cent annually (Unesco 1980). The increasing population has resulted in smaller farms and larger cities, as well as a rising demand for animal protein. What meat cannot be produced within each country must be imported. In Nigeria, for example, if per capita production and consumption rates of animal protein remain unchanged, in 1985 an estimated 200,000 tons of animal protein will have to be imported.

At present, many African villagers derive their animal protein from forests and secondary growth, which are havens for wildlife. As much as 50 per cent of the population south of the Sahara utilizes animal protein derived from nondomesticated species such as fish, insects, snails, and rodents. In the southern states of Nigeria, where trypanosomiasis has inhibited cattle production, wild or bush meat is particularly important. It constitutes an estimated 20 per cent of the animal protein consumed and has been valued at N30 million (Afoloyan 1980).

The replacement of natural forests with tree plantations will limit the availability of bush meat unless carefully planned so that there are young trees at all times to encourage its presence. One method is to extend tree planting over a period of years.

Cattle, West African Dwarf sheep and goats, and poultry are the main locally produced sources of animal protein in the humid zone of West Africa. As trypanosomiasis is endemic in the area, the breeds of ruminants present are mainly trypano-tolerant, i.e., they are generally resistant to the disease (table 1).

TABLE 1. Numbers of Trypano-Tolerant Livestock in Humid Tropical Africa (in millions)

Source: ILCA (1979)

In the expansion of livestock production, ruminants will be important, as they are able to use low-quality feeds, such as grass, that can be produced on marginal soils. As a result, these animals need not compete with humans for food or land on which crops are grown.

Limitations to a rapid increase in the ruminant population include disease, rate of reproduction, feed supply, and management. As there appears to be no imminent, simple, and broadly effective solution for trypanosomiasis, trypanotolerant livestock will continue to provide the bulk of the meat produced in the humid zones of West Africa. West African Dwarf sheep and goats have the potential to become a more important source of animal protein than cattle because they reproduce much more rapidly (1.5 offspring/year after the first year).

Current Management Practices

Up to 90 per cent of village families have three to five sheep and goats. Mortality is high because of disease and accidents, and offtake (sale or home consumption) averages about 15 per cent (Okali, personal communication).

Though animals are allowed to range freely, they graze and browse close to the village. Studies have shown (Carew 1981) that in the forest zone of southern Nigeria, West African Dwarf sheep and goats, respectively, spend 98 per cent and 95 per cent of their browsing/grazing time browsing. In the derived savanna, where there is a higher proportion of graminaceous species, the proportions of browsing/grazing time spent browsing are 47 per cent and 62 per cent. Household scraps-cassava, yam, banana and plantain peelings, and maize chaff-are considered critical in the diet of these animals and may determine the number of animals maintained by a household,

The figures on time spent browsing and grazing indicate that grass can form a substantial portion of the diets of sheep and goats, though the goats prefer browse. Browse feeding by cattle, sheep, and goats is standard in villages throughout the region, particularly in the dry season when the graminaceous and herbaceous fodder has been consumed or is of such low nutritive value as to be unpalatable. Browse species that are not deciduous provide green foliage throughout the dry season.

Leguminous browse is particularly nutritious. When six Species of browse were tested for nutritive value (Ficus exasperate, F. sp., Newbouldia laevis, Aspilia africana, Spondias mombin, and Cylicodiscus gabunensis) all had crude protein levels as high as Panicum maximum (13 per cent), with the maximum being A. africana at 17 per cent. All six species were at least as digestible in vitro as P. maximum (Carew 1981). The high nutritive values of the browse species and their potentially good dry season productivity suggest that they can reduce the current dependence on household scraps and make larger herds feasible.

Improvement of Ruminant Production

The provision of permanent pastures could eliminate the need for household scraps in the diets of the Dwarf sheep and goats of the region. Permanent pastures would be mainly considered for marginal lands where farm holdings are larger and where low rainfall, low soil fertility, or high susceptibility to erosion make cropping uneconomic.

Native species of grasses may provide adequate pasturage in the early rainy season, but as the pastures normally are composed of both palatable and unpalatable species, the palatable ones are heavily grazed and disappear from the paddock. The remaining grasses are usually early maturing and fibrous, and are thus of lower feeding value. If it were economic, it would be preferable to replace the native grasses with productive perennial species such as Panicum maximum, Brachiaria decumbens cv. Basilisk, or Cynodon neumfluensis cv. IB 8. Short cultivars should be planted for Dwarf goats as they will not graze in wet grass.

The addition of a selected forage legume of such genera as Stylosanthes, Centrosema, Desmodium, or Macroptilium to pastures can improve the productivity of the pasture. The forage legumes provide foliage of higher nutritional value than grass, and this value is maintained throughout the dry season. Nitrogen transfer from the legumes to the grass improves the growth of the grass, and because many legumes are deep-rooted they continue to grow longer into the dry season. Although the legume must be palatable, it should be of sufficiently low palatability to receive only minimal grazing until the dry season so that it accumulates as much dry matter as possible.

Although grasses provide adequate fodder in the wet season, and careful selection of herbaceous forage legumes may extend the value of the pastures into the dry season, the severity and length of the dry season in much of the humid tropics requires that other sources of feed be available. The preservation of feed as hay or the utilization of silage or fodder crops such as sorghum or maize is neither practical nor economic for a small farmer. Thus, the production of browse, as occurs in the villages, is probably the most viable solution.

Browse plantings in permanent pastures may be valuable for uses other than fodder. Leguminous trees enhance the growth of pasture grasses and improve soil fertility. The plants are sources of construction material and firewood for the farmer, and may be sold for timber. Other uses for browse plants include shade, living fences, and shelterbelts. Samanea (Pithecolobium) saman and Ceiba pentandra are two locally available species of trees that are browsed and that provide excellent shade and timber. Species such as Gliricidia septum, which readily sprout from cuttings, are useful for living fence posts. Though fairly weak for the first year or so until they are well rooted, they are fire" and rotresistant and can be pruned as a source of fodder. However, where there are extensive areas to be fenced and labour costs are high, it may prove expensive to prune the trees as often as necessary. Belts of trees providing timber, browse, and shade can be placed between the paddocks. These are less useful for temperature and wind control than in a temperate environment but may prove useful during periods of water stress by increasing the relative humidity in the adjacent paddocks (Marshall 1967). They may also extend the grazing time of goats by reducing the chill factor in rainy periods.

Browse may be planted in the pasture scattered throughout or in hedge rows several metres apart. It can be maintained at low heights so that it is available for browsing through the year, or it can be allowed to grow so that it can be cut for feed in the dry season.

Browse species are usually leguminous and may be shrubs, small trees, or large trees. Their agronomic characteristics should include leafy, vigorous growth, good seed production, a non deciduous habit in the dry season, deep rooting, ready coppicing, and palatability. They should be high in nitrogen and digestability, and have no toxic effects on the animals.

The species that has received most attention to date is the leguminous tree Leucaena leucocephala. Vigorous, palatable, and a heavy seed producer, it unfortunately can produce toxic effects because of its mimosine content (Jones 1979). Desmanthus virgatus (Skerman 1977) and Codariocalyx gyroides (Lazier 1981) have received some attention for possible use as browse. Gliricidia septum, a small tree used for living fence posts and as a shade plant in plantations, is of interest in West Africa because of its ability to establish from cuttings and its leafy and vigorous growth through the dry season.

It can be planted in paddocks in such a manner that the tops of the cuttings are above the browsing level of the the animals, thereby conserving the growth on the upper part of the cuttings for the dry season. Recent trials have demonstrated that sheep can be successfully fed diets of up to 80 per cent G. septum (Chadhokar and Kantharija 1980).

In Nigeria, initial trials with G. septum have indicated that 18 month-old cuttings will produce leaf dry-matter yields of 350450 9 in the dry season. If 600 9 of dry matter are required daily by each animal, two cuttings would supply the needs of one animal, and in a five-month dry season about 300 cuttings would be required per animal. With 15 animals/ha 4,500 cuttings would be required.

Planting at spacings of 0.5-1 m would require that one-tenth to one-half of a one-hectare paddock be planted to browse. As the cuttings became better established, fewer plants would be required to maintain the same number of animals and stocking rates could be increased.

West Africa, with its long history of domesticated grazing animals, has identified a wide variety of browse species. A literature survey that was not exhaustive has listed 95 tree and shrub species in West Africa. Little is known about methods of managing these species or of their effects on animals. Noteworthy among those on the list are the leguminous species Albizia adianthifolia, A. Iebbeck, A. zygia, Dalbergia sissoo, and Daniellia oliveri. Much work needs to be done in selecting vigorous species and cultivars from among those used in the villages.

Integration of Livestock with Forestry

Large areas of forests in Africa are managed for the production of timber, pulp, or firewood. Bush growth in the forests seriously concerns forest managers because it presents a fire hazard and competes with young trees. Although livestock can be used to control this growth, there are no reports indicating this practice in the tropics (Adams 1975). In favour of livestock grazing in forests is the fact that it reduces the costs of clearing the bush, and the savings can offset some of the costs of planting and managing the trees.

Studies have determined that the damage caused by cattle trampling and rubbing the trees, and sheep grazing them, can be minimized by good management (Adams 1975). Damage increases with the stocking rate and depends on such factors as the stage of growth of the trees and the season of the year. The pine forests of the southern United States are a good example (Halls et al. 1964) of how animals can be successfully raised in the forests. Goats, however, are not regarded as suitable for inclusion in forest grazing as they depend largely on young trees for browse. They also eat the bark of certain tree species. It has been observed in the International Livestock Centre for Africa (ILCA) Small Ruminant Programme in Nigeria that the West African Dwarf goat eats tree bark mainly during the dry season when there is a shortage of alternative feed. Thus, appropriate management, including adequate provision of feed, preventing grazing while the tree leaves are within reach of the animals, and the use of trees with unpalatable bark, is the key to successful grazing of goats in forests, particularly in forest plantations.

There are often problems, however, in the implementation of a grazing policy, for the time when bush clearing expenses are highest is when trees are youngest and most vulnerable to grazing and trampling. The provisions of fencing, water points, skilled personnel to manage the operation, and the infrastructure to support these is a major financial undertaking. As forests are commonly in remote and thinly populated areas, housing must be provided, and it is difficult to recruit good managers and staff. Also, livestock handling is difficult among trees, particularly over large areas. The remoteness of the operation encourages petty larceny in the removal of fences and rustling.

The large variation in feed supply throughout the year results either in a serious lack of feed in the dry season or in undergrazed bush in the wet season, with the accumulation of coarse, unpalatable material in the dry season. If livestock are to thrive, some provisions must be made to reduce the stocking rate in the dry season or to provide extra fodder. Forests are usually established in marginal areas either naturally low in fertility or degraded due to cultivation or overgrazing with consequent erosion. Such areas produce poor-quality forage and thus slow weight gains among the animals. Macro- and micro-nutrient deficiencies must be corrected before there can be successful livestock raising in forested areas.

The alternative to forestry-managed livestock raising is the rental of forest areas to livestock owners at specific times of the year, normally in the early rains when the vegetation is fastest-growing and most nutritious. A considerable degree of management would still be required by the forest manager to limit damage, but there would not be the high investments required of forestry-run operations.

Uncontrolled grazing of forests can result in an increase in fires, poaching of trees and firewood, damage to young trees, and deterioration of the soil due to over-grazing. Although the decisions on individuals' rights to forest grazing are often not in the hands of foresters, the existence of a well-reasoned grazing management system that balances the needs of the livestock owners with those of the forester may well return control of such grazing to the foresters.

One of the main impediments to integrating livestock with forestry is probably the hesitation of foresters to introduce new complications into a carefully controlled monocrop system. The inclusion of livestock management courses into forestry training may largely overcome this reluctance.

Integration of Livestock with Plantation Crops

The use of livestock, particularly cattle, under plantation crops to control grass and bush regrowth has been frequently recommended (Thomas 1978); maintenance costs are lowered while a further source of income is provided. The animals rapidly recycle nutrients through the production of faeces, and there may be an increase in soil fertility. Where leguminous crops are planted between the trees, these provide a nutritious source of feed for livestock, as do byproducts of tree crops such as rubber seed, palm kernel, and coconut meals. Grazing under plantation crops is particularly evident in the coastal coconut plantations of the humid zone of West Africa.

In a review of raising livestock on plantations, Thomas (1978) noted that plantations do not have a constant supply of fodder. Feed must be provided during the drier times of the year, and, as plantations are usually planted relatively rapidly, the large amount of fodder available when the trees are young is much reduced as they grow, only increasing again when they are tall and mature. Monoculture operations often do not have the trained personnel, facilities, or sufficient interest to develop such operations successfully. Cattle may knock off collection cups in rubber plantations, depress yields by soil compaction, puddle heavy textured soils, increase soil erosion, and remove nutrients.

Although oil palm production in large commercial operations on heavy soils may not be adapted for livestock raising, there is interest in such a system (Aseidu 1978; Boye 1968; Renault 1968), and commercial operations are possible. SODEPALM in the Ivory Coast has been raising cattle under oil palm since 1973, and in 1977 was grazing 4,000 head (Koua Brou 1977; see also the paper by Tchoume in this volume, pp. 111-114). Research on sheep has indicated that those grazing in oil palm plantations have their grazing pattern less affected by high temperatures and driving rain than do those in paddocks without such shelter (Aseidu 1978).

The scattered semi-domesticated stands of oil palm around the villages of West Africa also offer excellent opportunities for development as grazing areas. The lighter soils in many of these areas reduce the chance of compaction and puddling, and the sparse canopies allow greater light penetration. Some degree of management is, of course, necessary to prevent over-grazing, and there needs to be some provision of fodder, perhaps in the form of browse, for the dry season.

Sheep and cattle have been reported from many countries as having been successfully integrated with coconut plantations, for example in Tanzania (Childs and Groom 1963), Sri Lanka (Appadurai 1968), and the Philippines (Guzman and Allo 1975). In the Philippines, 22 per cent of coconut holdings are grazed, mainly by cattle, and in some areas this percentage rises to 60 (Barker and Nyberg 1968). Small ruminants are suggested as suitable for smallholdings and steeper land, and discing or subsoiling is recommended every four or five years to prevent reduced yields of fodder and nuts due to soil compaction (Guzman and Allo 1975). Increased coconut yields resulted from integrating cattle and coconut production (Childs and Groom 1963).

Livestock production has been reported as being low in combination with all of these tree crops, but the use of fertilizers and improved forage species has increased both coconut and livestock yields (Barker and Nyberg 1968). Providing leguminous browse species under the tree crop and cutting it as feed for the dry season may improve livestock yields without reducing tree crop yields. Extra paddocks for dry season feeding are another possible solution.

The addition of grazing animals to fruit orchards in an effort to control the understorey of bushes and grasses results in some reduction of fruit yields, particularly in the case of cattle, for the lower branches of the trees will be pruned and the fruit within reach will be consumed. Much less foliar damage would occur if sheep or goats were used, though the goats may damage the bark of some species. In peasant systems in which the farmer is more interested in flexibility of income rather than intensification of monoculture system, losses in fruit yields may be more than offset by the time, money, and energy saved in clearing and the greater financial flexibility offered by the system.

Alley Cropping

The establishment of pastures on exhausted cropping land with leguminous browse species in hedgerows leads naturally into an alley cropping system (i.e., planting crops in the alleys between rows of trees). Once the soil fertility and structure have been improved under the grass/tree combination, the alleys between the trees could be cultivated and cropped for a year or more. The land would then be returned to pasture. During the cropping cycle, uses of the browse would include either green manure year-round, green manure in the early wet season and cut-and-carry feed for livestock for the rest of the year, or cut-and-carry for the whole year with the animal manure returned to fertilize the crops. One possible constraint to such a system is the feeder roots of the browse, which may make cultivation difficult and compete with the crop for available water and nutrients.

Current Research

Current research in the ILCA Small Ruminant Programme in Ibadan involves village surveys to determine the constraints to livestock production in the villages, the effect of veterinary care on animal mortality, and the establishment of unit farms to develop the management systems required to raise small ruminants on pasture and browse. Preliminary screening of 23 native types of browse used in the villages is planned. The comparative value of a number of farming systems, both to the farmer and in terms of soil fertility maintenance, will be tested. Treatments will include permanent pasture with browse in hedges, alley crop-pasture rotations, cropping with the leaves of the alley tree species as mulch, and continuous cropping without alleys. Leucaena leucocephala and Gliricidia septum will be the browse species utilized.

Intercropping of terminalia superba with cocoa and banana in mayombe, people's republic of the Congo

J.P. Koyo
Centre Technique Forestier Tropicale, People's Republic of the Congo

Abstract

The Mayombe forest is situated 70 kilometres north-east of Pointe-Noire, the economic capita/ and sole seaport of the Congo. Initially very rich in Terminalia superba, this forest was very heavily exploited.

In 1950 an extensive limba (Terminalia superba) planting programme was implemented to ensure sustained production of this species. In addition, experimental limbacocoa and limba-banana intercropping was undertaken in sample plots. Although limba-banana intercropping yields are encouraging for both plants, the same is not true of the limba-cocoa intercrop. After 15 years problems arise with regard to the silvicultural management of the limba- especially thinning-and root competition between the two species.

Farmers often intercrop food plants with T. superba. This should be encouraged, provided that farmers take sufficient care during clearing and burning.

Research should be carried out to determine factors likely to affect the success of new techniques. Finally, an effort should be made to educate and inform the people of these new planting methods.

Introduction

Mayombe is a very rugged forest zone starting some 70 km north-east of Pointe-Noire and stretching to Zaire and Cabinda. The Mayombe forestry station was set up around 1927 on the first buttresses, about 80 kilometres from the coast. The area has a subtropical, semi-humid climate. The rainy season begins in November and ends in April, with a break of variable duration between December and February. Rainfall varies between 1,300 and 2,300 mm, but it is : usually around 2,000 mm. The heaviest rainfall is generally in November or MarchApril. The dry season is characterized by four to five ecologically dry months during June to October. It is marked by a low saturation deficit and an abundance of morning fog. Normally temperatures fluctuate around 25°C, but during the dry season they are about 18-22°C.

The natural vegetation is semi-deciduous forest that is rich in limba (Terminalia superba). The overstorey species frequently found growing with T. superba are: Desbordesia pierreana, Dacryodes pubescens, Irvingia gabonensis, Combretodendron africanum, Gambeya africana, Staudtia stipitata, Pentaclethra macrophylla, Baillonella toxisperma, and Dialium spp. Until 1950 the work carried out at this station consisted mainly of setting up a tree nursery of about 20 ha and studying the silviculture of a few native species. As a result of the heavy exploitation of limba, especially in the wake of the Second World War, an extensive planting programme was begun. Between 1950 and 1961, 6,435 ha of limba were established in order to ensure a steady production of timber. The limba were planted from two centres fairly close to each other-Nboku-Nsitu, situated at latitude 4°26' S and longitude 12°16' E, and Bilala, situated at latitude 4°30' S and longitude 12°13'E.

The Mayombe forest plantations have been established on extremely variable soils. For instance, stands are to be found on soils depleted by food crops, on relatively fresh and fertile alluvial soils, and on very fertile schistocalcareous and schisto-sandy soils. Limba does well on clayey soils with an adequate water content.

Demographic pressure is particularly high in the area covered by the limba plantations. Because of the dense population and the intensive agricultural activity, on the one hand, and the large area occupied by the limba stands, on the other, farmers sometimes intercrop banana, cassava, and cocoyam with the limba.

Every four years, the Centre Technique Forestier Tropicale du Congo (Tropical Forestry Research Centre of the Congo) evaluates the condition of these stands in a survey of onehectare sample plots, which include experimental limbacocoa and limba-banana combinations.

Forest management techniques likely to stimulate natural regeneration were not approved in the plantations. The same was true of artificial regeneration techiques that do not permit limba to receive the maximum amount of light, which is particularly important since limba is a very heliophilic species. For this reason, the corridor method was discarded. Taungya was also ruled out, although later at tempts at intercropping were made on a very small scale. The formula finally adopted consisted of planting pure, even-aged stands of limba, generally at a final spacing of 10 x 10 or 12 x 12 m. In general the following operations are carried out:

• A quick survey of the ground and vegetation one to two years in advance;
• Detailed survey: The area to be planted is mapped out in January-February so that the amount of labour needed can be determined and supervision planned;
• Clearing of the existing forest: An effort is made to destroy the forest as completely as possible before planting. The underbrush is cleared with cutlasses; the intermediate storey and overstorey are destroyed, with trees less than 30 cm in diameter being felled and the remainder girdled;
• Burning in the dry season, defining of plots, and the preparation of planting lines;
• Pegging or digging holes 10 x 10 or 12 x 12 m apart; and
• Planting at the beginning of the rainy season in November, using plants cultivated in nurseries for 16 months (stumps).

Limba-Cocoa Intercropping

An intercropping experiment with limba and cocoa was undertaken on a plot of 450 ha. The edaphic conditions of this plot are among the best in the area. The opening up and preparation of the land were carried out according to the method described above. Limba was planted in November 1954, 12 x 12 m apart. Cocoa was planted from 1963 to 1965 between the limba at a distance of 3 x 3 m.

Limba requires a very good soil, and, in the natural forest it generally grows in clusters on fine-grained, well -structured soils with good air- and water-permeability. It is an indicator of fertile soils and farmers rely heavily on its presence in choosing their farmlands.

Cocoa is a perennial crop with stringent edaphic requirements. It prefers soils with a deep profile and good structure, providing adequate air- and water-permeability. In the Congo, it does particularly well in red clayey soils with a favourable water content. In addition to an adequate reserve of mineral matter, the organic matter content is vital to the success of the plantation.

From the start, the combination proved very beneficial to the limba, as its growth surpassed all other plots. Competition from weeds was suppressed and the soil remained perfectly clean under the cocoa plants. About 1969, the growth (in girth and average volume) of the limba above cocoa slowed, in comparison with similarly fertile sample plots. This relative decrease was more noticeable on the 39 finest trees in the plot. It seems, then, that after about 15 years, the cocoa had entered into keen root-level competition with the limba.

Since the cocoa plantation was not properly followed up, reliable data are not available on the behaviour of the cocoa under limba. For an area of about 10 ha, production over the first four years (1970-1973) was 49 kg/ha, 67 kg/ha, 31 kg/ha, and 16 kg/ha, respectively. These relatively low production figures probably reflect, on the one hand, Mayombe's utterly marginal ecological conditions for the growth of cocoa and, on the other, the depressing effects of the limba.

Limba-Banana Intercropping

The limba-banana combination is very widely practiced both by the Office Congolais des Forets (Congolese Forestry Authority) -a national organization responsible for reforestation-and by the populations of Bilala, Bilinga, and the surrounding areas. The preparation of the land for bananas consists of totally destroying the existing vegetation under old limba. Holes are dug and sprouts planted at the beginning of the rainy season at spacings of 4 x 4 m. The most frequently planted species is Musa sapientum, usually the Gros-Michel variety. This type of farming had already been successful in the Mayombe region of Zaire (at Luki) in the 1950s (INEAC: National Institute for Economic Study of the Congo).

Annual yields of bananas have been approximately 3 t/ha. The limba benefits greatly from the maintenance work done on bananas. Competition at root level is minimal, because of the creeping nature of the banana's roots and the banana's life span, estimated at about ten years.

Intercropping of Limba with Other Crops

As a result of increasing demographic pressure in the area, farmers quite often combine several food crops-such as cassava, plantain, cocoyam, corn, yam, and vegetables- with limba. Because these crops are neither perennial nor deep-rooted, there is very little risk of competition. However, it should be noted that cassava is likely to make the soil acidic.

The great danger in intercropping limba with other food crops lies in the fact that traditionally these crops are grown on burned areas. Farmers therefore tend to burn their land before planting without taking the necessary precautions to protect the limba. The trees wither very rapidly because the species is sensitive to heat.

Conclusion

Agro-forestry is a method of land use that has been practiced successfully in several tropical countries such as Burma, Java, India, Malaysia, and Nigeria. Its success in the Congo will depend initially on the solution of certain technical and educational problems.

From a purely technical point of view, it is essential that foresters and agronomists carefully select the species to be intercropped. This choice must naturally take into consideration the nature, requirements, and optimum ecological conditions of the agricultural and forest species being considered. From this point of view, the intercropping of limba with cocoa in Mayombe is not advisable for several reasons:

• From the climatic and edaphic point of view, Mayombe is far from suitable for cocoa farming;
• Like limba, cocoa is a perennial and very demanding as far as soil is concerned;
• The limba sheds its leaves during the dry season, thereby exposing the cocoa to the harsh, dry weather; and
• Because of the perennial nature of cocoa, certain silvicultural treatments-such as thinning-are difficult to carry out.

The intercropping of limba with banana, however, is relatively promising inasmuch as banana is a shorter-lived perennial than is cocoa and has a shallow root system.

After suitable species have been identified for intercropping, it is important to perfect plantation management techniques (opening up of the land, burning, time of planting for both crops, type of maintenance, and so on), which are necessary to the success of the operation. Burning should be prohibited.

Inasmuch as this method of regeneration is closely linked to the rural areas, it is vital that an effort be made to educate and inform the people, to give them an understanding of the value of, and prerequisites for, success with the new planting techniques.

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