Minimum tillage and vegetative barrier effects on crop yields in relation to soil water content in the Central Kenya highlands

► Our study investigated the effects of minimum tillage and vegetative barriers on soil and water management and, crop yield in a steeply sloping sub-humid zone of central Kenya highlands. ► Farming without installation of vegetative barriers on the steeply sloping cropping fields where permanent soil cover is inadequate led to soil degradation due to intense soil and water losses regardless of the tillage practice. ► Installation of Napier or leucaena vegetative barriers reversed this trend and this should be considered in design of approaches where implementation of the three principles of conservation agriculture is not feasible or insufficient. ► Leucaena barriers with minimum tillage have a complementary water use pattern with crops and would be suitable for incorporation into smallholder farming systems in sub-humid areas where water stress is likely to occur. However, they are less efficient for capturing rainwater particularly on steep sloping arable land. ► Napier barriers on the other hand are efficient in capturing rainwater but when combined with minimum tillage would be less suitable for sub-humid areas due to strong competition between crops and barriers for available water even when intensely harvested. The sub-humid zone of Central Kenya is water deficient due to regular intra-seasonal dry spells that constrain rain-fed crop production. A study was initiated to investigate the effects of minimum tillage and vegetative barriers on soil and water conservation and crop yield. There were two tillage practices; minimum and regular tillage and two vegetative barriers; ‘leucaena’ consisting of leguminous trees (Leucaena trichandra), and ‘Napier’ consisting of Napier grass (Pennisetum purpureum) in addition to a control without barriers. Maize and soybean crops were planted in rotation in the terraces between the barriers. Soil moisture content was measured near the barriers and at the centre of the terraces. Vegetative barriers impeded run-off and controlled soil loss. There was a positive linear relationship between soil loss and rainfall for Napier grass barriers. For leucaena barriers, soil loss increased quadratically with rainfall. At the onset of rainfall, soil water content increased for all tillage and barrier practices. With more rainfall, soil water content increased marginally without barriers while with barriers there was continued soil water build-up. At the end of the wet period and across tillage practice, the soil contained 43% mor