Abstract
ABSTRACT Evaluating the impacts of water stress on crop yield allows comparing irrigation management alternatives, aiming to ensure an economic return for the irrigated farms. Thus, the main objectives of this study were to model the soil water balance, deriving the crop coefficients, grain yield prediction, and economic return of soybean grown at different levels of water deficit and price quotations. The experiment was carried out under a rainout shelter, using four irrigation water managements. Irrigations were applied when the soil available water in the root zone reached 75%, 64%, 60%, and 50% of the total available water (TAW). Crop and soil parameters were monitored throughout the crop season. The SIMDualKc model was used to simulate the soil water balance. Statistics indicators demonstrated the goodness of the simulation, with regression coefficients (b0) ranging from 0.96 and 0.99 and root mean square errors (RMSE) ≤8.4 mm. Crop coefficients for initial, intermediate, and final stages were calibrated and validated at 0.15, 1.00, and 0.10, respectively. Crop yield and economic return were higher for the treatment kept at 75% of TAW, results that should be considered in irrigation management programs.
Highlights
Soybean (Glycine max L.) is the major oilseed crop cultivated worldwide
In the initial stage, available soil water data (ASW) remained above 85% of the total available water (TAW), in all treatments
With the restriction of available water, ASW decreased until it exceeded the readily available water (RAW) line, from 100, 69, 61, and 55 DAS, for treatments 75%, 64%, 60%, and 50% of TAW, respectively
Summary
Soybean (Glycine max L.) is the major oilseed crop cultivated worldwide. In Brazil, the total cultivated area of soybean reached 34 million hectares, producing 114 million tons per year, with the State of Rio Grande do Sul responsible for nearly 17% of the country’s production (CONAB, 2019).Globally, irrigated agriculture uses nearly 70% of the freshwater annually withdrawn from any water resource (UNESCO, 2018). Soybean (Glycine max L.) is the major oilseed crop cultivated worldwide. In Brazil, the total cultivated area of soybean reached 34 million hectares, producing 114 million tons per year, with the State of Rio Grande do Sul responsible for nearly 17% of the country’s production (CONAB, 2019). Irrigated agriculture uses nearly 70% of the freshwater annually withdrawn from any water resource (UNESCO, 2018). Irrigation management can be improved by adopting deliberate deficits that while affecting negatively crop evapotranspiration (ETc) and grain yield, maintain a positive economic return (Rodrigues et al, 2013).
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