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 that Acacia albida has effects on maize similar to those reported in the Sahel, Sudan and Ethiopia. Yield and soil trends were evaluated along transect lines at increasing distances from individual trees in different orientations extending away from the tree canopy. Exploratory studies along the lakeshore plain of Lake Malawi during the 1987/1988 season showed that yields of local maize under traditional management with A. albida were more than double the yield away from the trees. However, the soil fertility status changed little over the length of the transects. Later studies were conducted inland from the lake with hybrid and local maize. Soil differences were again minimal. Hybrid maize (NSCM41 and R201 ) generally outyielded local maize, but the size and period 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 management by the farmer, and proximity to neighbouring trees. The relative contributions of these factors are not known, indicating areas for further research. Because of the on-farm nature of these trials, control over external influences was limited, suggesting the need to standardize cropping practices and other factors across sites if the mechanisms affecting yields are to be better understood.