Simulation of Yield Decline as a Result of Water Stress Using BUDGET Model

In this paper, to account for the effect of water stresses in the various growth stages under deficit irrigation, the multiplicative, seasonal and minimal approaches are integrated in the BUDGET model. To evaluate the model, the simulated yields for winter wheat (was grown in Sharif Abad district) under various levels of water stress were compared with observed yields. The result showed, simulated crop yields agreed well with observed yields for this location using multiplicative approach (in comparison with minimal and seasonal approaches). The determination coefficient (R2) between observed and simulated yields ranged from 0.81 to 0.92 with very high modeling efficiencies. The root of mean square error (RMSE) values is relatively small and ranged between 6 to 14. A sensitivity analysis showed that the model is robust and that good estimates can be obtained by using indicative values for the required crop and soil parameters.