ALLEY CROPPING WITH GLIRICIDIA-SEPIUM ON A HIGH BASE STATUS SOIL FOLLOWING FOREST CLEARING - EFFECTS ON SOIL-CONDITIONS, PLANT NUTRITION AND CROP YIELDS

Interactions between Gliricidia sepium (Jacq.) Steud., the crops maize and upland rice, and soil conditions were investigated in an alley cr opping experiment on a Ferralic Cambisol/Plinthic Lixisol in the rainf orest area of the Cote d'Ivoire. Conventional and mulched sole croppin g treatments were included for comparison. Hedgerow integration signif icantly reduced N and Mg losses from the soil. These effects were neit her observed in the mulched sole cropping treatment nor reduced by hed gerow root barriers, suggesting that they were not direct consequences of the input of hedgerow biomass into the soil. Crop yields were incr eased in the central part of the alleys as compared to sole cropping, but the effect was offset by the loss of cropped surface which was occ upied by the hedgerows and by yield depressions at the tree-crop inter face. Gliricidia mulch increased foliar nutrient concentrations of mai ze; however, unlike mineral fertilizer the mulch had no influence on t he imbalance between low P and high K levels in maize leaves. Nutrient accumulation in the dry season vegetation tended to be higher in alle y cropping than in sole cropping. Weeds were particularly efficient in accumulating those nutrients which were relatively low in the hedgero w biomass. Necessary improvements to the cropping system are discussed . The optimum composition of fertilizers in mulching systems deserves attention.