Simulating soybean irrigation scheduling using BUDGET model

Precise prediction and scheduling of plant irrigation water can increase water use efficiency while preventing possible periodical stress. In this study، the performance of BUDGET model in irrigation scheduling was assessed and compared with real data under soybean deficit irrigation water management under two consecutive years 2008 and 2009. The experiment was conducted in the form of randomized complete blocks design in four furrow irrigation treatments each with three replicates. The treatments include full irrigation، (control)، conventional deficit irrigation at 50% and 75% of the soil moisture deficit compensation، and partial root drying treatment at 50% of the soil moisture deficit compensation. The results indicated that the performance modeling indices of RMSE and CRM in 2008 were 3. 91 and -0. 18 and in 2009 were 4. 76 and -0. 11، respectively. The obtained EF index was 0. 69 and 0. 78 in 2008 and 2009، respectively، indicating that the model performed acceptable predictions of crop yield. The overall results revealed that the use of BUDGET model by adjusting crop coefficients in different growth stages، soil and plant characteristics can provide more acceptable outputs. Further، the sensitivity analysis indicated that BUDGET model is less sensitive to irrigation water depth and initial soil water content in the full irrigation treatment.