Irrigation strategies on crop and water productivity of sunflowers based on field experiments and modeling1

Soil water balance models can be a good option for studying crop growth and yield responses under different water supply levels. The aim of this study was to evaluate the effect of different irrigation strategies on sunflower yield and water productivity using field experiments and soil water balance simulations. Two field experiments were performed. In 2018/19, four irrigation strategies (aimed at maintaining soil available water at 80, 70, 60, and 50% of total available water) were evaluated. In 2020/21 an irrigated and a rain-fed treatment were evaluated. The SIMDualKc model was calibrated and validated to simulate soil water balance and derive the dual coefficients using plant variables from field observations. Grain yield was highest in the treatment maintained at 70% of total available water in Study I, suggesting that a water replenishment reduction strategy may be an alternative to irrigation management, especially in locations where water is scarce. The statistical indicators showed good performance of the model in simulating the water available in the soil, with the coefficient of determination > 0.90 and modeling efficiency above 0.86 for all cases. The study allowed the calibration of the single and basal crop coefficients of sunflower, which are important parameters for irrigation management.