Do rotations and intercrops matter? Opportunities for intensification and diversification of maize-based cropping systems in Zambia

Abstract

ContextRealizing the double-edged goals of food security and crop diversification require knowledge of crop yield response to different agricultural practices and the extent to which such response is context dependent. This is particularly important in Southern Africa where cropping systems are dominated by maize and smallholders use few external inputs. ObjectiveThe objectives of this study were (1) to evaluate the performance of cropping systems with different levels of legume diversification and intensification on maize productivity across the main agroecological zones and farming systems of Zambia, and (2) to establish the minimum land required to reach maize self-sufficiency at household level with the different cropping systems tested. MethodsSix maize-based cropping systems, comprising maize monocropping, maize-legume rotations and intercrops under ‘conventional’ tillage and conservation agriculture, were evaluated across 40 farms in contrasting agro-ecological zones and farming systems of Zambia. A household survey was conducted in the same communities hosting the on-farm trials to quantify the share of households with enough maize cultivated area to benefit from the tested cropping systems. ResultsMaize yield measured in the on-farm trials ranged, on average, between 3.6 and 5.4 t ha−1, which was greater than mean maize yields reported by farmers not hosting on-farm trials during the same growing seasons and in the same sites. Our results showed a clear positive effect of legume rotation on maize yield in Eastern province only, where cropping systems including groundnut as rotation crop yielded between 1.0 and 2.0 t ha−1 more maize than other cropping systems. Pigeon pea intercrops and Gliricidia hedgerows, crop residue management, and tillage practice had no significant effect on maize yield in any of the provinces. Finally, nearly 35, 50, and 70% of surveyed farms in Northern, Eastern, and Southern province would have enough land to achieve the same level of maize production obtained on their farm with the yields, and associated area requirements, of the maize-legume rotations tested in the on-farm trials. ConclusionLegume rotations can increase maize productivity on land abundant farms in high potential maize production areas of Southern Africa, whereas legume intercrops have benefits at cropping systems level and should be targeted to land constrained farms. SignificanceThe study contributes to better understand the niche for diversified maize-based cropping systems with legume rotations and intercrops in Southern Africa, along with their impacts on maize productivity at the field level and their land requirements at the farm level.