Social and Economic Factors for the Adoption of Agroforestry Practices in Lake Victoria Catchment, Magu, Tanzania

Abstract

An African Green Revolution cannot succeed without a secured supply of mineral fertilizers. This is particularly true of phosphorus, one of the key essential macronutrients. In most tropical soils, P is one of the main limiting plant nutrients and its deficiency is a major constraint for better crop production. This is mainly attributable to (i) the low total P content in soil, (ii) the relative unavailability of inherent soil P for plant uptake, and lastly (iii) the relative speed at which applied soluble sources of P such as inorganic P fertilizers and manures become fixed or changed to unavailable forms. It is clear that mining P minerals and spreading P fertilizers over the landscape is not sustainable in the long run. Cultural practices which can secure P sources and which conserve P should be made use of. Some of the measures necessary to adequately address the P problem can be listed as follows: • nutrient cycling through the recycling of crop residues, green manures, animal manures, domestic and industrial wastes; • the integration into the cropping system of P-mobilizing plant species which show the ability to improve P uptake even from less labile P forms and store P in the aboveground biomass even in excess of their needs; and • biological means making use of mycorrhiza and other soil fauna to help extract fixed P from deep soils under low pH conditions. African Green Revolution must put a lot of emphasis on integrated soil fertility management (ISFM), which combines the use of plant residues and inorganic P fertilizers exploiting their high potential for increasing crop production and ensuring sustainability. Increased production and productivity should never be based on addressing the constraints surrounding inorganic (mineral) fertilizers alone.