Maize yield effects of conservation agriculture based maize-legume cropping systems in contrasting agro-ecologies of Malawi and Mozambique

Sustainable intensification cropping systems involving improved maize and legume seeds and conservation agriculture (CA) are potential avenues towards improved productivity. This study evaluated CA based cropping systems effects on maize yields with respect to herbicide use, crop establishment techniques and legume rotations in four contrasting agro-ecologies of Malawi and Mozambique from 2010/11 to 2013/14. No significant (p > 0.05) yield differences, at 4100 versus 3900 kg ha(-1) were observed in Malawi when CA was implemented with and without herbicides respectively, suggesting herbicides were not a precondition for CA's success. CA basins depressed maize yields by 3 % in north-western Mozambique and also offered no advantages in Malawi's lowland districts (Ntcheu and Salima). In contrast, significant yield gains (p < 0.05) emerged from dry Balaka (<600 mm year(-1)) with mean yields of 2400 from the CA basins compared to 1800 kg ha(-1) from farmer practices, an effect also confirmed by the yield stability analysis showing CA basins superiority in unfavourable rainfall environments. Thus CA basins performance was site dependent with no benefits on waterlogged soils or high rainfall conditions where direct seeded dibble stick or jab planting provided a better crop establishment option. Across all agro-ecologies, soyabeans, cowpea and groundnuts rotation systems, significantly increased maize yield, amounting to 20, 38 and 54 % respectively, except for the maize-common bean rotations in north-western Mozambique, which failed to offer any yield advantages. Probabilities of achieving higher CA yield ranged from 58 to 71 %. The study suggests CA based cropping systems offer an opportunity for intensifying maize production in the region.