محسن رمضانی واسوکلائی

Simulation models are suitable tools for predicting the effects of different management scenarios and selecting the most appropriate solutions in agricultural production systems. In this study, after evaluating the efficiency of the DSSAT model, the effect of water table management on rice growth and yield was investigated. The required field experiments were performed under a randomized complete block design with four irrigation treatments and three replications during a rice growing season in a research farm at the Sari Agricultural Sciences and Natural Resources University. Irrigation treatments included conventional or flooding irrigation (control) with water height of 5 cm above the soil surface (I1), water table control at soil level (I2), water table control at 5 cm below soil surface (I3) and water table control at 15 cm below soil surface (I4). During rice growing season and at harvest, leaf area index, shoot weight, plant height, number of tillers, biological yield and grain yield were measured. The data of I1 treatment were used for calibration and the data of other treatments were used for validation of the model. In both calibration and validation processes, the DSSAT model showed a good performance for predicting phenological dates, leaf area index, biological yield and grain yield. In the calibration and validation stages, root mean square error (NRMSE) values were in the range of 0.7-7.6% and 1-7.6%, respectively, and Wilmot agreement index (d) values were in the range of 0.73-0.99 and 0.82-0.99, respectively. Effects of irrigation treatments were significantly different on plant height, number of tillers per hill, leaf area index, grain yield and biological yield. Among different treatments, the highest grain yield was 5584 kg ha-1, related to the control treatment. Grain yield in I2, I3 and I4 treatments was 4.7, 4.6 and 39.2% lower than that in the control treatment, respectively. Water use efficiency in I1, I2, I3 and I4 treatments was 0.48, 0.65, 0.83 and 0.73 kg m-3, respectively. Based on the results, in order to maintain rice production while saving water, it is recommended to control the water table at a depth of 5 cm below the soil surface.