Agroforestry In Acid Soils Of The Humid Tropics

Abstract

The majority of the soils in the humid tropics are acidic and infertile. Agroforestry systems are the most appropriate forms of sustainable, productive management of soils in the humid tropics because perennial woody vegetation can recycle nutrients, maintain soil organic matter, and protect the soil from surface erosion and runoff. This chapter evaluates three agroforestry systems that are helpful to overcome these constraints to production—namely, alley cropping systems; managed leguminous fallows to accelerate the restoration of soil fertility and reduce the duration of the fallow period; and fruit tree-annual crop sequential cropping systems. These technologies represent a range of agroforestry options, the suitability of which will vary with the relative availabilities of land, labor, and capital. Alley cropping may contribute to the maintenance of soil fertility under annual cropping by improved nutrient cycling, but the system's total labor and possibly capital requirements are likely to be greater than those with shifting cultivation. Hence, the system seems appropriate for situations of limited land availability. In contrast, managed fallows might reduce the duration of the fallow period and improve productivity per unit time by accelerating weed suppression and nutrient accumulation in the fallow biomass. This system requires relatively small quantities of labor and capital, but like most fallow-based systems, it requires moderate to high land availability. Finally, cultivation of fruit trees can help alleviate labor and capital constraints by spreading labor over periods of low demand and by providing additional income through the sale of fruits and other products.