Processos hidrodinâmicos no solo como preditores da eficiência de aplicação da água no cultivo da soja irrigada

Abstract

The practice of irrigation has become essential for agricultural production and expansion. However, when managed inappropriately or inefficiently, it further enhances the global demand for water and significantly accelerates the unavailability of water resources in many parts of the world. Research and experiments involving soil water dynamics are of paramount importance to obtain data to optimize the application of water. However, most of these experiments are carried out in the field and have high costs. However, models such as SWAP (Soil-Water-Atmosphere-Plant) and Hydrus- 1D are used to obtain field-specific information quickly and flexibly. In this context, the present work Evaluates the hydrodynamic processes in the soil as predictors of the efficiency of water application in the cultivation of irrigated soybeans through the measurement and modeling of water processes in the soil for the cultivation of irrigated soybeans in the Western and Recôncavo regions of the State. from Bahia. Therefore, this research was developed in two parts. The first part of the work was developed in the western region of the state, an important region for soybean production, in which the efficiency of central pivot irrigation was evaluated based on measurements of soil hydrodynamic processes. Subsequently, the influence of the protocols for obtaining the hydraulic properties of the soil (in laboratory and by inverse modeling) in the use of the SWAP model, in the simulation of hydrodynamic processes in the soil in irrigated soybean cultivation, was verified. Finally, the SWAP model was used to simulate different scenarios of central pivot irrigation management in soybean, aiming to obtain strategies to maximize the efficiency of water use. By simulating the volumetric soil water content using SWAP, from hydraulic parameters obtained by inverse modeling (Hydrus-1D), results were obtained closer to the real (measured) than when using the hydraulic parameters obtained. by the laboratory method. This enabled the establishment of optimized irrigation scenarios, maximizing the efficiency of soil water storage and minimizing water waste. The second part of the research was developed in the Recôncavo Sul region of Bahia, with the determination of soybean crop evapotranspiration by the water balance equation and strategies performed by SWAP simulation, in which irrigation scenarios were proposed, based on in the principle of fixed regime by the model. The results showed that the average evapotranspiration rate of the crop was 4.64 mm day-1, with this demand being more demanding in the reproductive phase, especially in the R5 stage, period of filling the crop's grains. The strategy proposed by SWAP, the readily available water depletion method, met satisfactorily, taking into account the previously established soil water limits.