Effect of tillage, mulching, herbicide application, intercropping and agroforestry on soil moisture maize yield and rainwater use efficiency in semi-arid Kenya: A case study of Laikipia East

Abstract

Conservation agriculture (CA) is promoted in Sub-Saharan Africa to address land degradation and low productivity among small-scale farmers. However, contrasting results have been reported from studies testing the impact of CA on land degradation and productivity. This study was conducted to investigate the effect of tillage, mulching, herbicide application, intercropping, and agroforestry on soil moisture storage, crop yield, and rainwater use efficiency (RWUE). Three main treatments consisting of conventional tillage (CT), no tillage (NT), and no tillage with herbicides (NTH) were tested. In each of the treatments, four sub-treatments, which included (a) maize and beans, (b) maize and dolichos, (c) maize, beans, and leucaena, and (d) maize, beans, and mulch (1.5 metric tonnes Ha-1) replicated three times, were investigated. This implies that a split-plot design with 3 main plots and 4 subplots was used. The experiments ran for a period of three years and were characterised by two years of wetter than average. Tillage significantly affected crop yield, soil moisture, and RWUE during the dry year, with CT showing a significantly lower 33.9% and 33% maize yield and RWUE, respectively, than NT. Similarly, mulching significantly increased maize yield and RWUE by 13% and 19.8%, respectively, in the same year. Maize yield and RWUE were significantly increased in treatments that had agroforestry by 16% and 15.8%, respectively. By extension, it means that agroforestry has a positive impact on maize yield, soil moisture, and RWUE. The study showed that NT and mulch are critical aspects of CA in that they avoid drought stress on maize during dry seasons while enhancing maize yield. Agroforestry showed potential to further improve CA in semi-arid zones, resulting in higher yields in dry years. Even though the dry growing season under study corresponded with a meteorological drought, practicing two or three CA practices could avoid agricultural droughts due to the conservation of soil moisture that becomes available to crops during dry periods. The ‘best’ practice (no till with maize, beans, and mulch) resulted in up to 74% higher yield in the dry year and still up to 24% higher yield in the wet growing season under study, compared to the conventional practice. The study concludes that NT, mulching, and incorporating agroforestry in CA had a significant effect on soil moisture, maize yield, and RWUE, especially in seasons with rainfall below normal. Keywords: conservation agriculture, tillage, mulching, herbicide application, agroforestry, soil moisture