Evaluation Of The Applicability Of Aquacrop Model To Simulate Crop Response To Deficit Irrigation

Abstract

Water is a scarce resource and requires the development of new strategies to save water and energy that improving water use efficiency. Simulation models are useful tools for improving farm-level water management and optimizing water use efficiency. The field study was carried out to evaluate the effects of different levels of irrigation water application imposed at different growth stages of haricot bean and validate the AquaCrop model with the outcome of field study under Melkassa climatic condition. The treatments considered in the field experimentation were 100% ETc,75% ETc, 50% ETc, and 25% ETc applications under the four growth (Initial, development, mid-season, and late-season) stages of haricot bean. The treatments were arranged in a randomized complete block design with three replications. The AquaCrop model was calibrated using experimental data collected from 100%ETc application during all growth stage and model performance was evaluated in simulating haricot bean yield, biomass, and water use efficiency. The result from the experiment showed that the highest yield of 2.5603 ton/ha was found from the control treatment where 100% ETc was applied during all growth stages and whereas a minimum yield of 1.123 ton/ha was obtained from 25%ETc application in all growth stages of haricot bean. The highest (1.06 kg/m3) and lowest (0.65 kg/m3) water use efficiency was recorded under treatment irrigated with 50% ETc and 100% ETc throughout the growth stage, respectively. Yield predictions over a wide range of values were very good, with RMSE of 0.26 ton/ha, Willmott?�?s index degree of agreement of 0.825,, and the coefficient of determination of 0.951. The field study indicated that the haricot bean was sensitive to moisture stress during development and mid-growth stages. Therefore, applying moisture stress during development and mid-stages had significantly reduced the yield of haricot bean, and also for enhancement of water productivity without a significant yield reduction applying irrigation at the initial and late stages is recommended. The results of this study showed that the aquacrop model is capable of simulating above ground biomass, water use efficiency and grain yield of a haricot bean for treatments with some water deficit; but under sever water deficit condition the model performed less satisfactorily.