THE EFFECTS OF ACACIA-ALBIDA ON SOILS AND MAIZE GRAIN YIELDS UNDER SMALLHOLDER FARM CONDITIONS IN MALAWI

Research conducted in different ecological zones of Malawi indicates t hat Acacia albida has effects on maize similar to those reported in th e Sahel, Sudan and Ethiopia. Yield and soil trends were evaluated alon g transect lines at increasing distances from individual trees in diff erent orientations extending away from the tree canopy. Exploratory st udies along the lakeshore plain of Lake Malawi during the 1987/1988 se ason showed that yields of local maize under traditional management wi th A. albida were more than double the yield away from the trees. Howe ver, the soil fertility status changed little over the length of the t ransects. Later studies were conducted inland from the lake with hybri d and local maize. Soil differences were again minimal. Hybrid maize ( NSCM41 and R201 ) generally outyielded local maize, but the size and p eriod of sampling were too limited for conclusive results, especially regarding crop sustainability. Overall yield patterns were similar to the lakeshore area, but differences were more variable. This appeared to be a function of variability in tree size and shape, soils, crop ma nagement by the farmer, and proximity to neighbouring trees. The relat ive contributions of these factors are not known, indicating areas for further research. Because of the on-farm nature of these trials, cont rol over external influences was limited, suggesting the need to stand ardize cropping practices and other factors across sites if the mechan isms affecting yields are to be better understood.