EFFECTS OF NO-TILLAGE AND ALLEY CROPPING ON SOIL PROPERTIES AND CROP YIELDS IN A TYPIC KANDIUDULT OF SOUTHERN CAMEROON

The effects of no-tillage and alley cropping with Cassia spectabilis hedgerows on soil properties and crop yields in a Typic Kandiudult of the humid forest zone of Central Africa were studied over the period 1990-1992 in southern Cameroon. The experimental treatments were no-tillage and hand tillage, both of which were either alley cropped with C. spectabilis hedgerows at interhedgerow spacings of 6 m or not alley cropped (control). A maize + cassava intercrop was planted in all plots at the commencement of each growing season. No-tillage had no significant effects on soil physical properties except to decrease soil temperature. In comparison to hand tillage, no-tillage increased soil organic C and total N in both years and pH in 1991. Mean organic C and total N with no-tillage were 1.77% and 0.174%, respectively, whereas with hand tillage were 1.35% and 0.145%, respectively. No-tillage also resulted in a greater proportion of C. spectabilis roots occurring in the topsoil. Alley cropping caused significant reductions in dry season soil temperature, surface seat formation and cassava root growth, and increases in exchangeable Ca, effective CEC and water infiltration compared with non-alley cropped controls. Infiltration rate at 2 h after commencing measurements were greater by 75% with alley cropping. Lowest maize cob and cassava tuber yields were observed when no-tillage was combined with alley cropping whereas highest yields occurred with no-tillage alone.