23. Use of Conservation Tillage and Cropping Systems to Sustain Crop Yields Under Drought Conditions in Zambia

The adverse effects of climate change on agricultural productivity have been evident for several years. Factoring climate change risks into critical decision-making is crucial for ensuring food security. Zambia has adopted conservation agriculture in response to two real threats to food security: loss of animal draught power due to livestock disease, and poor yield and occasional total crop failure due to frequent drought. The main threats from climate change arise from the stresses and shocks caused by high temperature and erratic rainfall, such as shorter growing seasons and water deficit in the soil profile. Under these conditions, conventional tillage practices and a few of the current cropping systems have proved inappropriate and inadequate for sustaining high crop yields. For instance, the national long-term average yield of maize under conventional agricultural practices has declined by 40 %. In this paper, I discuss conservation tillage (CT), soil quality management, and crop and cultivar options for adapting to and mitigating the adverse effects of climate change with the aim of ensuring stable yields. In drought years, employing CT involving deep ripping (15–30 cm), leaving crop residues on the soil surface, and using an appropriate maturity cultivar have consistently resulted in yield increases of 30–70 % (with maize showing the highest yield increase) compared with conventional practices. Early planting is an important factor, and 45 % of the yield increment could be attributed to it. Both physical (plow pans) and chemical (subsoil acidity) impediments to soil depth can greatly restrict root growth into the subsoil and severely restrict the volume of soil exploited and, in turn, the quantities of nutrients and water available to the crop. This investigation shows that adopting a technology package of appropriate culture practices, and seed and crop management can potentially reduce the negative effects of drought and stabilize crop yields.