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