Benefits and challenges of crop rotations in maize-based conservation agriculture (CA) cropping systems of southern Africa

Abstract

Conservation agriculture (CA) based on minimum soil disturbance, crop residue retention, crop rotations and associations are being promoted in southern Africa to reverse the decline in soil fertility and crop productivity. While agronomic benefits of rotations are known, farm level benefits of rotations in CA systems and how they fit in the smallholder farming systems have not been sufficiently addressed. This paper summarizes agronomic results from 2005 to 2011 of maize in rotation and association with different crops in Malawi, Mozambique, Zambia and Zimbabwe. Rotation with or without legumes improved water infiltration (between 70 and 238%), soil moisture, soil carbon, macro-fauna and crop productivity. However, due to poor market conditions, rotations with legumes were less profitable than maize during the study period. Farmers have fewer difficulties to abandon tillage and there is scope to retain crop residues in situ in areas of limited crop–livestock competition but the adoption of rotations and associations is constrained by socio-economic factors that need to be addressed before all principles of CA can be applied.