Alley farming as a potential agricultural production system for the humid and sub-humid tropics

It is widely recognized that the biggest challenge facing agricultural research in the Tropics is the development of farming systems capable of ensuring increased and sustained productivity with minimum degradation of the soil resource base. Reversing the trend of declining per capita food production in sub-Saharan Africa, therefore, does not depend solely on the development of improved and high-yielding crop varieties. Development of sustainable production systems is necessary to foster and maintain advantages derived from such improved varieties. The issue of sustainability has received considerable attention in recent years in agricultural research and development (CGIAR, 1990). The nature of much of the upland soils in the Tropics is such that over exposure and over cultivation can easily lead to their degradation. According to the Soil Management Support Services (1986), agricultural land in most humid and subhumid tropical regions is dominated by low activity clay (LAC) soils whose inherent characteristics and limitations make large upland areas dominated by these soils less suitable for conventional mechanized and high-chemical input farming methods. These soils have inherently low fertility, and are highly erodible when left unprotected. Nutrient loss through run off and erosion can, however, be kept to a minimum by using appropriate production systems that minimize disturbance and ensure a protective cover of the surface soil through live or dead mulches (Lai, 1986). Management of vegetation within the cropping system also could contribute to maintenance of soil fertility and enhance the stability of the cropping system (Juo & Lai, 1977; Lal et al., 1978). In the Tropics, trees have long been recognized as essential both for the stability of the environment and for maintenance of soil fertility for crop production. Trees have been recognized as major elements in soil fertility regeneration and conservation as reflected by their prominence in tradition.

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