Improving water saving, yield, and water productivity of bean under deficit drip irrigation: Field and modelling study using the SALTMED model*

A field experiment was conducted over two successive seasons of 2017 and 2018 in Egypt. The aim was to study the effect of irrigation systems (surface and subsurface drip irrigation) and irrigation amounts (100%, 80%, and 60% of crop evapotranspiration, ETc) on the yield of bean crop (Phaseolus vulgaris) and evaluate the SALTMED model performance on simulation of soil moisture, total dry matter, and yield. Despite the highest yield values being achieved with the 100% of ETc treatment, there were no significant differences between the 100% and 80%. This means a water saving of 20% can be achieved without significantly compromising the yield. Yield and water productivity under subsurface irrigation was slightly higher than under surface drip irrigation. This is because under subsurface drip irrigation, there is no wetted surface area contributing to evaporation losses as is the case for surface drip. In addition, the soil moisture under subsurface drip is kept within the root zone for the longest possible time without subjecting the crop to water stress. The SALTMED model accurately simulated soil moisture, total dry matter, yield, and water productivity. Hence, the model could be applied as crop, water, and land management tool under current and future Egyptian climatic conditions. (c) 2020 John Wiley & Sons, Ltd.