Limits of conservation agriculture to overcome low crop yields in sub-Saharan Africa

Abstract

Conservation agriculture (CA) has become a dominant paradigm in scientific and policy thinking about the sustainable intensification of food production in sub-Saharan Africa. Yet claims that CA leads to increasing crop yields in African smallholder farming systems remain controversial. Through a meta-analysis of 933 observations from 16 different countries in sub-Saharan African studies, we show that average yields under CA are only slightly higher than those of conventional tillage systems (3.7% for six major crop species and 4.0% for maize). Larger yield responses for maize result from mulching and crop rotations/intercropping. When CA principles are implemented concomitantly, maize yield increases by 8.4%. The largest yield benefits from CA occur in combination with low rainfall and herbicides. We conclude that although CA may bring soil conservation benefits, it is not a technology for African smallholder farmers to overcome low crop productivity and food insecurity in the short term. Principles of conservation agriculture are widely promoted for sustainable agricultural intensification, but their effects on crop yields in sub-Saharan Africa are poorly understood. A meta-analysis covering 16 countries quantifies such effects and reveals the conditions under which they are maximized.