Simulating water productivity of paddy rice under irrigation regimes using AquaCrop model in humid and semiarid regions of Iran

Rice production in the world is heavily dependent on water. Therefore, increasing in water productivity with appropriate irrigation management is necessary. Simulation models that illustrate the effects of water on crop growth can apply to optimize water productivity and improve farm irrigation management. This study was conducted to simulate water productivity of paddy rice using AquaCrop model in both humid and semiarid regions of Iran. Required data for running model were gained from two field experiments: an experiment with a lowland local rice cultivar named Champa-Kamfiroozi in a semiarid climate (Kooshkak), and other experiment with two lowland local rice cultivars named Binam and Hasani in a humid climate (Rasht). Both experiments were conducted under five irrigation treatments in two consecutive years. As a result, the relative root mean square error (RRMSE) of grain yield simulation was gained between 2.28 and 15.09%. The ranges of water productivity based on transpiration (WPT) and water productivity based on evapotranspiration (WPET) as affected by irrigation treatments, in dry climate were greater than wet climate. The averages of WPT and WPET for continuous flooding in the humid (1.21 and 0.82 kg m−3, respectively) and dry (1.26 and 0.76 kg m−3, respectively) climates showed the role of evaporation losses in decreasing WP in dry climate. The highest ET was obtained in continuous flooding treatments that the amount of evaporation for dry climate was 88% higher than humid climate.