Innovative water management strategies to maximize rainfed wheat productivity in Iran’s arid zones

Abstract This study aimed to optimize water productivity and wheat yield in the rainfed wheat systems of the Honam plain, a critical region in the upper Karkheh River basin of Iran. In the first two years of research (2013–2014 and 2014–2015), the prevailing status of the region was investigated with regards to wheat yield and rainfall productivity under rainfed conditions. Thereafter, different management scenarios were defined and investigated to improve wheat yield, rainfall productivity, and water productivity. In the second year of research (2014–2015), the best management scenarios selected from the first two years were tested in some selected rainfed wheat farms in the Honam plain. The results showed that wheat biomass and grain yields from these best scenarios under rainfed and single irrigation (SI) conditions could be accurately predicted using the AquaCrop model. At the model validation stage, the RMSE was 0.16 for grain yield and 0.32 ton ha−1 for biomass and the NRMSE was 5 and 4%, respectively. Whether for grain yield or crop biomass, the coefficient of determination was about 0.86. The proposed scenarios for AquaCrop modelling were then trialed for rainfed wheat and showed better agronomic advantages than the traditional crop management practices. By applying a single irrigation in spring, the mean total water productivity (rainfall + irrigation) for wheat increased to 0.70 kg m−3, being 74% higher than that under rainfed conditions. The best management plan in the Honam plain was the combination of superior crop management with single irrigation in spring (60 mm) during the mid-flowering period, which increased the grain yield by 176% and rainfall productivity by 134%. The results from this management scenario were satisfactorily simulated by the AquaCrop model.