عنوان مقاله [English]
Considering limitations of agricultural productions in arid and semi-arid regions, optimization of irrigation depth and leaching is very important. In this study, calibrated and validated AquaCrop model was used in order to optimize irrigation water depth and leaching for two varieties of winter wheat (Ghods and Roshan) in Birjand region and one variety of wheat (spring Roshan) in Mashhad region. For winter wheat, irrigation treatments included 125%, 100%, 75% and 50% of water requirement and water salinities of 1.4, 4.5, and 9.6 dS/m for winter wheat. For spring wheat, irrigation treatments consisted of 100%, 90%, 65%, and 40% of water requirement and water salinities of 0.5, 0.9, 5.25, 8.6, and 10 dS/m. The coding written in Matlab program was linked to the AquaCrop in order to achieve the optimized values of irrigation and leaching in the land constraint conditions. The optimization results showed that net profit for the best irrigation and leaching management at all salinity levels and different wheat varieties, except for salinity levels of 8.6 and 10 dS/m in the spring Roshan variety and level of 9.6 dS/m in the winter Roshan variety, was more than the current management in field conditions. The increases in profits in optimal management compared to the current management for Ghods variety at the salinity levels of 1.4, 4.5, and 9.6 dS/m were 51.4%, 78.9%, and 142.5%, respectively. For the same salinity levels for Roshan variety, the increments were 42.7%, 20.8% and -0.3%, respectively. The increase in profits in optimal management compared to the current management for the spring Roshan variety at the salinity levels of 0.5, 0.9, 5.25, 8.6 and 10 dS/m, were 5%, 13.2%, 34.3%, -27.7%, and -51.4%, respectively. In general, the results show that in the regions where drainage problem due to irrigation water is an important environmental problem and causes dissatisfaction among the downstream farmers, applying less water and accepting negligible decrease in the benefits (minimum 0 and maximum 29%) could resolve the problem.