Simulação do balanço hídrico sequencial e da necessidade de irrigação para a cultura da soja em vinte anos agrícolas

Abstract

Due to the importance of soybean cultivation for the state of Rio Grande do Sul and the variability of rainfall throughout the agricultural years, which impact the productivity of this crop, studies evaluating the need for supplemental irrigation are crucial for decision-making by farmers and public authorities. Therefore, the objective of this study is to simulate the sequential water balance and irrigation requirements for soybean cultivation over a period of 20 agricultural years (2001 to 2022) in the edaphoclimatic region of Cachoeira do Sul, RS. The sequential water balance simulations for soybean cultivation were conducted using the CROPWAT 8.0 model. An initial modeling was performed based on observed data during a field experiment with soybean cultivation in the 2021/22 agricultural year, where all the necessary input data for modeling were collected. Subsequently, 20 additional simulations were carried out for all agricultural years between 2001-2 and 2021-22, keeping the modeling parameters from the 2021-22 agricultural year and modifying only the rainfall during the crop cycle. Out of the total, there were nine years with above-average rainfall, requiring an average of 129 mm of supplemental irrigation, and eleven years with below-average rainfall, with an average demand of 205 mm of supplemental irrigation. The need for supplemental irrigation depends on the regular distribution of rainfall throughout the cycle to maximize the utilization of effective rainfall.