INTRODUCTION
The main traditional land use system for food production in tropical humid Africa is the shifting cultivation-bush fallow system. Long fallow periods, ranging from 5–10 or more years, depending on the crops cultivated and available land, were the normal practice. With such long fallow periods, full vegetation regeneration and soil fertility restoration were possible and the system was ecologically balanced and sustainable.
With rapid population growth and increasing demands for food and other competing land uses, fallow periods are continually being reduced, with a resultant decline in soil fertitility and productivity. In addition, a greater area of cultivated land has been used in response to the increased requirements for crops.
Both the reduction in the fallow period and the expansion of cultivated land have resulted in an ecological imbalance and land degradation which, according to FAO (1982), are responsible for excessive “savannization” and “grassification” in the sub-humid zones. Efforts are therefore being made to develop more sustainable and productive land use systems to restore and maintain the ecological balance and soil fertility on a long-term basis.
Agroforestry techniques which involve intercropping of leguminous or non-leguminous trees and shrub species with food and forage crops have been particularly exploited for this purpose. Alley cropping for food crop production and alley farming for both crop and animal production are two such agroforestry technologies.
In the drier savannah zones, three types of farmers are in competition for a limited and dwindling land resource: the pastoralists who migrate in and out of the zone and therefore appear to have unlimited grazing, albeit of poor quality; the cultivators who are not only expanding their cultivated areas but are also degrading the land through reduced fallow periods; and the agro-pastoralists who have limited grazing resources for their large livestock herds. The last of these (agropastoralists) have no tradition of fodder cultivation and their livestock therefore suffer from qualitative as well as quantitative feed shortages, particularly during the long dry season, with resultant weight loss and poor productivity. The fodder bank concept was developed to alleviate this constraint and improve livestock performance.
DEFINITIONS
Alley cropping
According to Kang et al. (1984), alley cropping (also known as hedgerow intercropping or avenue cropping) is an agroforestry system in which food crops are grown in alleys formed by hedgerows of trees and shrubs, preferably legumes. The hedgerows are cut back at planting and periodically pruned during cropping to prevent shading and to reduce competition with the associated food crops, but allowed to grow freely to cover the land when there are no crops. The system has been described as an improved bush-fallow system, as it retains the basic features of the latter but is improved in the sense that the cropping and fallow phases take place at the same time and on the same land, thus allowing more intensive cropping for a longer period of time. A summary of other differences is shown in Table 1.
Alley farming
The alley cropping system extended to include livestock by feeding a portion of the hedgerow foliage to animals was described as alley farming by Okali and Sumberg (1985). Both systems are similar, except that hedgerow management differs when the purpose includes animal feed production. Alley farming in its purest form essentially promotes croplivestock integration and the production of a mulch for improved crop production is still one of its objectives. In alley farming most of the hedgerow foliage is used as mulch during the wet, crop growing season, particularly during the early growth phase, while a higher amount goes for animal feed during the dry fallow period. Thus foliage pruning must be strategically managed to satisfy both requirements.
A field data-based model developed by Sumberg et al. (1985) adequately demonstrates the crop-livestock integrating purpose of alley farming. The authors reported that about 80 kg mulch nitrogen would be required to maintain a base maize yield of 2t/ha, decreasing annually by 20% because of soil infertility. A one hectare alley farm producing 6 tons dry matter of foliage would supply this with 2.8 tons of dry foliage at 2.9% N. The surplus 3.2 tons would be sufficient to supplement 29 goats for one year, at the rate of 300g of foliage/day.
BUSH FALLOW | ALLEY CROPPING |
---|---|
- Mixed native woody species | - Selected woody legumes |
-Irregular planting pattern | - Planted in hedgerows |
- Trees and shrubs cut back and burned before cropping to release nutrients | - Periodic pruning of trees and shrubs for use as mulch and green manure |
- Growth controlled by fire | - Periodic hedgerow pruning |
- Allows short-term cropping following fallow | - Allows continuous cropping |
Source: Kang et al. (1986)
ALLEY FARMING MANAGEMENT
Legumes are usually prefered as hedgerow material for alley farming, although some non-leguminous tree species could also be used. The more important factor is the suitability of the plant to the agro-ecological and soil conditions. According to Kang et al. (1984), results of several trials conducted in the humid and sub-humid lowland areas indicate that Leucaena and Gliricidia are the most suitable species for alley farming in these zones. Others (Wildin, 1986) have suggested that Gliricidia should be limited to the humid areas only, while Sesbania grandiflora can be incorporated into alley farming in both the humid and sub-humid areas. Other species that have been tested and found suitable for other agro-ecological zones and soil conditions are: for humid highlands, Sesbania sesban and Cajanus cajan; for semi-arid highlands, Casia spectabilis and Calliandra; and for humid lowlands with acid soils, Acioa barterii and Ingas edulis (Kang et al., 1984).
Hedgerow management
In the alley farming system, food crops such as maize and cassava are grown in 4-metre alleys between established trees which are pruned at various times to prevent shading of the crops. The prunings are applied as green manure and mulch to improve crop production. Okali and Sumberg (1985) suggested that, since the primary objective of the smallholder farmers is to obtain satisfactory crop yields, only 25 % of the prunings should be fed to livestock and the rest used as mulch. Evidence exists, however, that the crop response varies with the stage of growth at the time of application of the mulch. Results from IITA suggest that prunings applied close to planting maize, for example, gave greater yield responses than those applied after tassling. Hence, as suggested by Kang et al. (1984), while all pre-planting prunings of alley trees should be used as mulch, all or a large part of later prunings could be fed to livestock without markedly depressing crop yields. In other words, a greater proportion of the foliage than suggested by Okali and Sumberg (1985) could be used as feed. Indeed most of the dry season prunings, when they are not needed for crops, could be used as fodder.
Studies need to be carried out to determine more precisely the optimum partitioning of alley farm prunings for use as mulch or fodder. The role of manure from animals should be quantified, together with the relative advantages of using tree foliage directly as mulch, or indirectly through animal manure.
Intensive feed gardens.
Alley farms could also be managed for fodder production only, by planting trees alone or in tree-grass combinations, in the intensive feed garden system. According to Atta-Krah (1989), this system is especialy suitable for livestock farmers willing to invest in pasture production.
In the tree-grass version, tree rows are spaced 2.5 or 4 metres apart with 2 or 4 rows of grass respectively in the alley. Yields of 20 tons of dry matter were reported for Leucaena-Panicum maximum combinations in the humid zone (Atta-Krah and Reynolds 1989). The productivity of tree-only plots, which allow more management flexibility, depends on interrow spacing and cutting frequency. Atta-Krah (1989) reported an annual yield of 30t dry matter/Ha from a combination of 0.5 m interrow spacing with a cutting interval of 12 weeks for Leucaena-only plots in the humid zone.
The intensive feed garden system has been evaluated by the ILCA Humid Zone Programme in East and Western Nigeria, where the average sheep and goat holding per household is about 3–4. It was reported that fodder from tree-only intensive feed gardens with an average size of 0.01 ha could provide sufficient browse in a cut and carry feeding system to meet 12.5% of the daily dry matter requirement of the animals.
BENEFITS AND PROBLEMS ASSOCIATED WITH ALLEY FARMING
Some of the documented benefits of alley farming include:
CROP | TREE SPECIES MULCH | RESPONSE %INCREASE OVER CONTROL | REFERENCE |
---|---|---|---|
Maize | Pigeon Pea | 63.1 | Onim et al. 1990 |
Sesbania | 75.5 | ||
Leucaena | 68.2 | ||
Maize stover | 38.1 | ||
Maize | Leucaena | 76 | Jama et al. 1991 |
Maize | Leucaena | 52 | Akonde et al. 1986 |
Gliricidia | 43 | ||
Cajanus | 35 |
Labour requirements
The major problem with alley farming is the high labour input required to prune trees and incorporate mulch into the soil. ILCA workers estimated a labour requirement for pruning of 18 days/ha, which is higher than traditional labour requirements. Incorporation of a livestock component in a cut and carry system will further increase the daily labour requirement. Nevertheless, some data exist which show that labour required for clearing fallow land on alley farms is lower than that for fallow in the traditional farm. It is also claimed that, although more labour is required in alley farming, less fertilizer and herbicides are required. In other words, alley farming may indeed be economically viable in certain circumstances. Proper cost-benefit analyses are therefore essential.
FODDER BANKS
Fodder banks are enclosed areas of forage legumes reserved for dry season supplementary grazing of cattle (Saleem and Suleiman, 1986). The concept was developed in the humid zone of Nigeria by ILCA scientists and has been mainly tested in this area with some measure of success. The main objective of fodder banks is to overcome the protein deficiency of the grass which is of low quality in this zone and fluctuates seasonally, with protein content often going below the 6% required for adequate intake.
It is argued that including forage legumes in the diet of livestock would be of value here. Legumes were chosen because they are usually higher in protein and minerals, consumed better and have a higher digestibility than associated grasses at similar stages of growth. The legumes of choice relied on to date has been Stylosanthes guianensis cv. Cook and S. hamata cv. Verano. The guidelines worked out for establishing and managing a fodder bank, according to Saleem et al. (1986) are:
The fodder bank is usually located close to the homesteads to ensure proper management and minimise misuse.
Management of fodder banks
Fodder banks should be managed to ensure high productivity and dominance of the legume at the end of the growing season, as well as its persistence. Some of the factors identified as being important for long-term persistency of stylo in the fodder banks include: grazing pressure, soil fertility and fertilizer application, nitrogen output to the soil/plant system, other fodder species in the pasture and time of first rains (Saleem et al., 1986).
Under controlled experimental conditions, these factors were addressed, and the productivity, quality and persistence of the legumes were satisfactory. During the testing and validation phase managed by the agro-pastoralists, certain changes were made to the proposed management package in order to reflect the realities of the terrain.
Some of these changes listed by Saleem et al. (1986) include:
The results of these changes, which were rational to the farmer, were reflected in the reduced quantity, quality and persistence of farmer-managed fodder banks (Table 3).
PARAMETERS | AGE OF BANK (YRS) | STATION MANAGEMENT | FARMER MANAGEMENT |
---|---|---|---|
Total yield (kg DM/ha) | 1 | 6824 | 7111 |
2 | 7350 | 5278 | |
3 | 4748 | - | |
4 | 6546 | - | |
Stylo yield (% total) | 1 | 56 | 68 |
2 | 55.4 | 64.5 | |
3 | 62 | - | |
4 | 61 | - | |
Seeds recovered/m2 | 1 | 941 | 1529 |
2 | 2839 | 1372 | |
3 | 2745 | 1824 | |
4 | 3102 | - |
This experience stimulated ILCA scientists to initiate remedial research. According to Saleem (1991), some of the new elements introduced to accomodate farmers concerns include: alternative land preparation methods to alleviate the fear of worm infestation; a search for productive disease-tolerant legume species to suit different ecological niches within the sub-humid zone, in order to ensure longer persistence; introduction of nitrogen-demanding cereal crops to alternate with years of legume growth to take advantage of and reduce soil nitrogen and reduce fertilizer input; the development of mini fodder banks of 0.25 ha adapted to small ruminant production by smallholders.
FUTURE PROSPECTS
Although the fodder bank concept has been shown to be a feasible, the rate of adoption by farmers has not been impressive. Perhaps not because of technical viability but due to socio-economic constraints such as land tenure insecurity and lack of infrastructural support. The technology was developed for the sub-humid zone and its central element, the Caribbean stylo, does not permit its extension outside the zone without further refinement. The length of the growing period in the drier areas is too short to support the generation cycle of the plant and, in the wetter areas, the challenge of anthracnose is too high. These limitations must be addressed in order to adapt the fodder bank concept to other regions.
CONCLUSION
The increasing demand for food in tropical Africa will continue to stimulate competition for the limited available land for crop and livestock production. An attractive solution to this problem is to encourage crop-livestock integration. Alley farming, intensive feed gardens and fodder banks provide for this integration and ensure a more rational and efficient use of the limited land resources. All three techniques have been shown to benefit the soil-plant-animal complex and should be exploited. Problem areas highlighted need to be examined and solutions found for adapting the systems to the different ecological regions.
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