Estimation soil water content under deficit irrigation by using DSSAT

Crop models need more evaluation and study for use in deficit irrigation. The main objective of this paper was to study the efficiency and accuracy of DSSAT model, in estimating of moisture in the soil profile under two levels of water application¬¬¬ in silage maize field. Two irrigation treatments including deficit irrigation (0.7 SMD), and a full irrigation (SMD) were considered for two years. Soil moisture was measured daily in different layers of the soil profile. After the model was calibrated, the results of the model were compared in soil profile with measured values in the field. The results indicated that RMSE of model in estimating soil moisture for different treatments, depending on depth, is between 1.8 and 13.6 percent volumetric moisture. Systematic error of model in estimating total water in the soil profile was between 1.985 and 5.7. On the other hand, the greatest error in estimating moisture has always happened in the first layer of the soil profile. Overall, considering the nature of water movement in the soil, the DSSAT model could be recommended to be used in deficit irrigation conditions.