Measuring and modeling evapotranspiration, yield and water productivity of maize under different agricultural management practices

Due to increasing global population and pressure on non-renewable soil and freshwater resources, feeding the future is a challenge that needs to be tackled through a lens of water productivity. More than 80% of the world agriculture is rainfed, and this leads to low crop yields in semi-arid regions (including the study area) that experience low and unreliable rainfall. To improve crop yield per drop of rainwater, we need management practices that reduce water loss from the field through evaporation so as to increase plant available water and yield. Three management practices were tested for their ability to reduce soil evaporation (Es), improve crop yield and water productivity at the field scale. The treatments; flat cultivation with mulching (FCM), without mulches (FC/control treatment) and double digging (DD), were tested and replicated thrice in three consecutive seasons. The data were collected by field measurements and analysed using simulations by AquaCrop model. Field measurements included weather, soil hydraulic properties, agronomic and crop data. The FAO AquaCrop model simulated canopy cover, biomass, soil moisture content, evapotranspiration (Es+Transpiration), final crop yield and the crop water productivity. AquaCrop adequately simulated the daily canopy cover, biomass accumulation and soil moisture contents under all treatments for all seasons. The biomass accumulation was slightly overestimated in a control treatment close to the end of one the seasons, which was associated with higher canopy cover also observed that plot. The simulated final crop yield agreed well with that observed in all treatments. The model simulated daily evapotranspiration poorly but the seasonal averages were close to the observations and therefore was acceptable for our purposes. The final water productivity simulated by the model was close to that observed for all treatments in all seasons. FCM improved the water productivity by 55% and DD by 16% compared to the control with no mulch. The model need revision for ET partitioning to improve its performance.