Using EPIC to simulate the effects of different irrigation and fertilizer levels on maize yield in the Eastern Cape, South Africa

Growing water scarcity and increasing Nitrogen (N) fertiliser prices in South Africa require more prudent N fertiliser and irrigation water use approaches. If the goal of sustainable agricultural intensification is to be realised, it is vital to develop location-specific agricultural land management strategies that promote increased crop productivity while minimising negative environmental impacts. In this study, a calibrated and validated Environmental Policy Integrated Climate (EPIC) model was used to simulate a range of N fertiliser and irrigation water levels on maize (Zea mays L.) yield in the Eastern Cape of South Africa. Results showed that a fertiliser and irrigation water management schedule combining approximately 200 kg N ha-1 and 580 mm irrigation water per maize growing season provided the highest average maize yield of 12.2 Mg ha-1 (an increase of +69% above farmers’ current maize yield levels). Nitrogen fertiliser application levels greater than 160 kg N ha-1 resulted in potential N fertiliser leaching losses of more than 35 kg N ha-1. The EPIC model can be considered a valuable tool to aid decision-makers in identifying optimal, site-specific irrigation water and N fertiliser application levels that contribute to increased maize crop productivity while maximising water use.