Abstract
In this study, we investigated the optimum irri-gation regime for a sand dune soil field using a numerical simulation model. For this purpose, we used HYDRUS-1D to simulate the soil water regime in the root zone of an irrigated sand dune soil and evaluated the effects of irriga-tion scenario (matric potential threshold for irrigation and daily irrigation depth) on the cumulative irrigation amount, cumulative water discharge from the root zone, ratio of cu-mulative irrigation amount over potential evapotranspira-tion, and ratio of transpiration reduction using the triggered irrigation module in HYDRUS-1D. When a soil water characteristic parameter determined from undisturbed soil samples in the laboratory was used, volumetric water con-tents simulated by HYDRUS-1D differed from field mea-surements (RMSE = 0.031−0.039). Estimation accuracy was improved using a soil water characteristic parameter derived from an inverse analysis (RMSE = 0.007−0.009). Based on the results of scenario simulation with differ-ent matric potential thresholds for irrigation and daily ir-rigation depths, the matric potential threshold set at −75 cm and the daily irrigation depth of 3.2 mm are recom-mended to decrease transpiration reduction and water dis-charge from the root zone.
