Can soil moisture and nutrient monitoring tools contribute to climate-smart smallholder irrigation? A modelling approach in Zimbabwe

Climate change is expected to significantly disrupt irrigation water availability, thereby threatening crop productivity and irrigators’ livelihoods. Studies have shown that the smart water management tools (SWM), the Chameleon sensor and Full-Stop wetting front detector, in combination with Agricultural Innovation Platforms, can improve irrigation efficiency and decouple crop production from water consumption. However, there is a need to further test the effectiveness of these SWM tools under projected climate change scenarios. This study applies the Agricultural Production Systems sIMulator (APSIM) to assess soil moisture and nutrient dynamics for maize production at a smallholder irrigation scheme in Zimbabwe. The simulation incorporated improved and unimproved irrigation practices under moderate- and high-emission scenarios. Agreement between simulated and observed water productivity confirms the reliability of APSIM to guide agronomic decisions. Results show that improved irrigation practice (through use of SWM tools) significantly improves maize yields (by over 50%), enhances water productivity (from 5.2 kg/m³ to 6.2 kg/m³, and sustains higher grain yields. While yield and water productivity will both decrease under future climate scenarios, the decline is less severe with use of improved irrigation practice (7–9%) compared to unimproved practice (15–17%). A combined analysis of irrigation practice and fertiliser application shows improved irrigation can stabilise yields, but having an optimum fertiliser rate has a stronger influence on maize productivity. Policy and development approaches that support access to the SWM tools, participatory learning platforms and climate smart agricultural education packages can improve irrigation, optimise fertiliser application, and build the adaptive capacity of smallholder irrigation systems.