THE IMPACT OF ALLEY CROPPING GLIRICIDIA-SEPIUM AND CASSIA-SPECTABILIS ON UPLAND RICE AND MAIZE PRODUCTION

G. sepium and C spectabilis hedgerows were established on slopes ranging from 18 to 31% in an effort to reduce soil erosion and improve upland rice and maize production. Upland rice and maize responded more to soil incorporated G. sepium biomass than to mulched C spectabilis. Incorporating hedgerow biomass equivalent to over 40 kg N per hectare, however, did not increase upland rice productivity. Maize, planted during the drought-prone second season, responded more than did rice to mulching. Crop performance improved along the slope gradient. Hedgerow-crop competition was observed at the upper and lower interfaces. Terracing intensified hedgerow-crop competition at the upper interface by reducing the crop's effective rooting depth. Under prevailing climatic and soil conditions, mixed hedgerows of C spectabilis and G. sepium initially produced approximately 7 tons of fresh biomass per hectare every 3 months. Four years after hedgerow establishment, however C spectabilis biomass was chlorotic and considerable mortality was observed, suggesting that C. spectabilis may be depleting soil N reserves.