Early Indicators of Change during Transition to Conservation Practices By Smallholder Farmers in Western Kenya.

Smallholder farmers in tropical Sub-Saharan Africa (SSA) produce maize (Zea mays L.) intercropped with common bean (Phaseolus vulgaris L.) using inversion deep tillage and low rates of fertilizers. Soils in this region are highly weathered, acidic and nutrient-poor. In order to produce sufficient amounts of food at low altitude areas, farmers grow maize/beans biannually during long and short rain seasons unlike high altitude farmers who obtain proportionally greater yields during one long growing season only. Second planting during biannual cropping requires additional tillage and leads to low nutrient recovery from crop residues and gradual exhaustion of soil organic matter (SOM) and high greenhouse gas (GHG) emissions. Implementing alternative conservation agriculture (CA) practices in these two agricultural regions is often met with limited success of acceptance by smalholder farmers due to limited understanding of the short return benefits during the process of transition. One of the critical factors is weed population management. We investigated the effects of reduced tillage combined with cover cropping on changes to greenhouse gas (GHG) fluxes, weed population, growth performance and operational costs associated with weed management. Proposed conservation practices included three tillage practices: farmer practice (FP), minimum tillage (MT) and no-till (NT) were combined with three cropping systems; current farmer practice of continuous maize/common bean intercrop (TYPICAL), maize/bean intercrop plus velvet bean (mucuna pruriens) relay after bean harvest (RELAY); and strip cropping of maize, common bean and velvet bean (STRIP). The conclusions from this study suggest that adopting CA practices that minimize tillage intensity especially during the short growing season improve SOM and rapidly reduce weed populations density.