Productivity or stability? Exploring maize-legume intercropping strategies for smallholder Conservation Agriculture farmers in Zimbabwe

Increasing threats of climate change and soil fertility decline enhance the risk of crop failure for smallholder farmers in southern Africa. The quest is to find cropping systems that provide yield stability while being sustainable. One of the strategies to use is intercropping legumes in maize-based Conservation Agriculture systems. Here, we present results of a three-year study in on-farm and on-station trials of Zimbabwe. We tested sole cropping compared to intercropping with different grain legumes and green manures as well as fertilizer application (in the case of on-station trials) on associated crop yields, total system yield, and yield stability. As methods, we used mixed modelling, best linear unbiased predictors estimation and additive main effects and multiplicative interaction analysis to analyse the data. The results show that intercropping systems with the selected legumes resulted in yield penalties. However, on-station sites showed maize/pigeonpea intercropping to be comparable to the sole maize in maize grain and biomass yield and to be superior in total system yield (108 GJ ha⁻¹ vs. 74 GJ ha⁻¹). Comparison of intercropping against sole cropping revealed that sole maize out-yielded all intercropping strategies in all environments on-farm while the maize/pigeon intercropping strategy out-yielded sole maize in almost all environments on-station. In general, total system yield of intercrops out-yielded sole maize in most environments signifying the ability of intercrops to enhance cropping system yields. Stability analysis on-farm showed that intercropping with cowpea and jack bean was more stable compared to sole maize as a result of better systems performance across the environments. On-station, the maize/pigeonpea intercropping strategy was in general the most stable. We conclude that intercropping is a viable option for smallholder farmers. However, there is need to investigate other crop arrangements to reduce competition for both maize and the intercrop and double-row strip cropping may be an option.