Evaluation and modification of model for the prediction of wheat yield at Iran region

摘要

In this study, the mentioned model was evaluated and modified for simulation of winter wheat (Sabalan cul.) under irrigated and rainfed conditions in Maragheh area (Eastern Azarbayejan province) of Iran for three consecutive crop years (1999 - 2000 to 2001 -2002). The simulated and measured grain yields were compared. Results show that the model was simulated satisfactory for the grain yield under irrigated condition, but the model was not able to simulate the grain yield under rainfed condition. The simulated grain yield was less than observed values under rainfed condition and it sounded that soil water content in this condition was simulated lower. Therefore, the coefficient of soil readily available water was changed from 0.65 to 0.90 for rainfed grain yield simulation. The model was able to predict more available water for plant transpiration using this scheme. The modified model properly simulated the grain yield under rainfed condition. Furthermore, it was found that this model was not able to simulate the grain yield for crop year (2001 - 2002) with high rainfall during the growing season in spring and summer due to plant disease infection. The amount of this rainfall was more than 140 mm and the model was modified for this parameter. Therefore, the modified model for excess rain was able to simulate the grain yield of Sabalan winter wheat under irrigated and rainfed conditions in the Maragheh area even for years with high rainfall during the growing season in spring and summer. Finally, the modified model was validated by data obtained for Alamoot cultivar and the results indicated that there was no significant differences at 5% level between measured and predicted grain yield.