Evaluation of the effect of some temperature and radiation methods for estimation of reference evapotranspiration (ETO) on maize actual evapotranspiration and biomass

Iran is located in the arid and semi-arid belt of the world, which is characterized by low rainfall, thunderstorms, flood flows, and high evapotranspiration. So, quantitative evaluation of evapotranspiration on a regional scale is necessary for water resources management, crop production, and environmental assessments in irrigated lands. In recent years, many crop models are developed for simulation of crop growth and yield in various fields and irrigation managements. These models can simulate crop growth and crop yield. AquaCrop model is a pervasive model and is developed by FAO that can be used in growth simulating and modeling of many crops. In this study, the effect of different methods for estimation of reference evapotranspiration (ETo) on actual evapotranspiration (ET) and biomass at five stations by AquaCrop model was studied and evaluated. For this purpose, the reference evapotranspiration rate was estimated by using two temperature methods and three radiation methods and the results were statistically evaluated by the reference method FAO-56. Based on the evaluation, temperature method, the Blaney-Criddle had for both parameters of ET and biomass in five stations with R2 value greater than 0.5 (strong), moderate to excellent NRMSE and NS close to one, the Turc and the Makkink, radiation methods, with R2 greater than 0.5, excellent NRMSE and NS equal to 0.99 for biomass in five stations were the best. Among the radiation methods for ET, the Priestley-Taylor method had medium and strong R2, good to medium NRMSE and NS equal to 0.96 in Qazvin and Mashhad stations and the Turc method with R2 greater than 0.5, excellent NRMSE and NS equal to 0.98 for Urmia had an optimal and better simulation compared to other estimation methods. Among the studied radiation methods, no suitable method was found to evaluate ET for Rasht and Yazd stations.