Due to limited water resources, efficient use of existing water resources is essential. To achieve the highest water use efficiency and crop yield production, it is necessary to manage correctly all factors that influence crop yield, such as planting date and use of soil moisture storage. For proper irrigation management, it is necessary to conduct researches to find out different management strategies. Since these methods are time consuming and costly, therefore the crop models which are faster to use and easy to apply are used. The objectives of this study were to evaluate the effect of different planting date of potato on irrigation water use efficiency, and to calibrate and evaluate the SUBSTOR-POTATO model for Burren hybrid of potato. The experimental treatments consisted of four planting dates of June 22 (PD 1 ), July 1 (PD 2 ), July 11 (PD 3 ) and July 21 (PD 4 ) using drip-tape irrigation system. The treatments were arranged in a strip-plot statistical design in a randomized complete block design with three replications for each treatment. Phenology indices, yield, irrigation water use efficiency (IWUE) and starch of potato were measured. The results showed that planting date had a significant effect (p 0.05) on total yield, one plant yield, IWUE, percentage of tuber dry matter, percentage of starch and plant height. The highest and lowest yield were 49.33 and 30.28 ton/ha for the PD 3 and PD 4 treatments, respectively. The highest and lowest IWUE were 6.45 and 4.23 kg/m 3 for the PD 3 and PD 4 treatments, respectively. The results indicated that the model was calibrated with very good accuracy. The comparision of measured and simulated data showed that the correlation coefficient (R 2 ) for fresh yield, dry yield and IWUE are 0.84, 0.53 and 0.93, respectively. Genetic coefficients derived from the calibration of SUBSTOR-POTATO model were equal to G2 = 2000, G3 = 25, PD = 0.9, P2 = 0.9 and TC = 17 for Burren hybrid of potato. The results indicated that the model simulate relatively well the tuber fresh yeild and IWUE, and simulate well the tuber dry yeild. Values of R 2 , d and NRMSE were 0.95, 0.8 and 30% for fresh yeild, 0.97, 0.96 and 14.43% for tuber dry yeild, 0.96, 0.84 and 30.8% for IWUE, respectively. The results indicated that change of planting date cause increase in total yield up to 38%, IWUE up to 34.4% and starch production efficiency up to 48.8%. The calibration and evaluation of the SUBSTOR-POTATO model provide the necessary basis to study different management strategies and to find out the best management solution for the situation of the water crisis in order to increase irrigation water use efficiency. Keywords : DSSAT, Planting date, Water use efficiency, Potato crop model
