Assessing water balance and yields in Malawian cropping systems : maize soybean and maize Gliricidia systems resilience against climate change

Abstract: In Malawi, maize monocultures are increasingly susceptible to extreme weather patterns, causing considerable yield reduction and heightened food insecurity for smallholder farmers dependent on rainfed subsistence agriculture. Diversifying cropping systems is crucial for ensuring yield resilience. The aim of this thesis was to explore water balances and yields across legume maize intercropping and agroforestry systems in rural Lilongwe, Malawi, under current and projected climate change scenarios. Hereby, the Agricultural Production Systems sIMulator (APSIM) maize and soybean baseline models were calibrated, using yield, management, and soil data from the International Institute of Tropical Agriculture (IITA) station trials conducted from 2018 to 2022 at the Chitedze Agricultural Research Station. Maize soybean intercropping and maize Gliricidia agroforestry systems were modelled in a present and three climate change scenarios using the Statistical Downscaling Model (SDSM). Climate prediction data was sourced from an ensemble of the Coupled Model Intercomparison Project Phase 6 (CMIP6) models. Main output parameters were single component and whole system water productivity, evaporative stress index and yields. While intercropped maize yields were higher by 2 t ha-1 compared to the monoculture system in the present scenario, long-term maize yields were higher by 1 t ha-1 in the agroforestry. This pattern was also observed in maize water productivity, which was higher in the long-term agroforestry system by 1 kg ha-1 mm-1. Soybean yields, and evaporative stress index were highest in the intercropping system across all scenarios with an average difference of 0.8 t ha-1 in soybean yields and 2.5 mm mm-1 in evaporative stress index compared to the sole soybean system. Therefore, I conclude that agroforestry maize systems will show higher yield and water productivity resilience under a long-term climate change scenario. Additionally, results suggest that maize soybean intercropping is more beneficial for water allocation and soybean yields than a mono cropped soybean system. More research and data collection needs to be done in the field of crop agroforestry to solidify presented modelling results.