Tillage and vegetative barrier effects on soil conservation and short-term economic benefits in the Central Kenya highlands

摘要

Minimum tillage and vegetative barriers can conserve soil and water resources in the steep-sloping highlands of East Africa but there has been little adoption by smallholder farmers. Soil conservation efficiency and short-term economic benefits provided by tillage and vegetative barriers were assessed over four cropping seasons to understand performance under local farming conditions. Minimum tillage was compared with regular tillage and vegetative barriers (leucaena and Napier) with no barriers. Maize and soybean yields were greater with than, without vegetative barriers, except with Napier barriers when minimum tillage was practiced where strong root competition occured. Cumulatively for the four cropping seasons, Napier barriers with regular tillage conserved most soil (72%) followed by Napier with minimum tillage (53%). The least soil (1%) was conserved for minimum tillage without barriers and leucaena barriers were intermediate in decreasing soil erosion. The highest positive marginal rate of returns (MRRs) were realized under leucaena barriers with regular tillage (2.09) followed by Napier with regular tillage (1.32). Minimum tillage without barriers had the lowest positive MRRs (0.08). Future increase in the price of key inputs would have greater depressive effect on the MRRs of Napier barriers with regular tillage than leucaena barriers with regular tillage. Minimum tillage without barriers was inefficient in soil conservation particularly when rainfall was intense and had poor MRRs. Leucaena barriers conserved less soil than Napier barriers but were more economically attractive, demonstrating a clear trade-off between soil erosion that is likely to impact crop yields in the long-term and short-term economic benefits. Napier barriers with regular tillage present a win-win scenario due to efficient soil conservation and attractive economic returns provided future prices of labour and Napier cuttings remain stable