SOME ASPECTS OF THE ROLE OF ORGANIC-MATTER IN SUSTAINABLE INTENSIFIED ARABLE FARMING SYSTEMS IN THE WEST-AFRICAN SEMI-ARID-TROPICS (SAT)

In this paper the role of organic manure in intensified farming systems in the SAT of West-Africa is discussed. Different aspects are treated: its function as a source of plant nutrients, its effects on soil physical and on soil chemical properties. It is concluded that often the major effect is through increased nutrient supply, but that in combination with chemical fertilizer - particularly nitrogen - it serves to counteract the negative effects of these fertilizers, particularly acidification and the increased removal of nutrients other than the one applied in the fertilizer. Insufficient organic material appears to be available to realize the required production increase and prevent the negative effects of nitrogen fertilizers. However, application of chemical fertilizer alone can lead to sustainable production systems provided export and losses of all nutrient elements are sufficiently compensated and acidification is avoided by using the correct type of nitrogen fertilizer, possibly in combination with liming.