Impactos das mudanças climáticas na irrigação, época de plantio e produtividade da cultura da soja em diferentes regiões brasileiras

Abstract

Agricultural production is affected by climatic factors, including concentrations of greenhouse gases, precipitation and temperature. Climate change in agriculture may bring irreversible damage, therefore, the adoption of strategies to mitigate such changes is essential to guarantee the production of soy in the world. The objective of this work was to evaluate the impact of climate change on the demand for irrigation water, soybean yield and planting time in different Brazilian regions using the AquaCrop-OS model. The AquaCrop-OS model, duly calibrated, was applied to determine the water demand for irrigation, soybean yield and future planting time, based on the ensemble of six global climate models from CMIP5 (Coupled Model Intercomparison Project Phase 5 ), for the intermediate emission (RCP 4.5) and high emission (RCP 8.5) scenarios, with reference to the present period (1980-2015), in four municipalities in the state of Bahia, three in Goiás, nineteen in Mato Grosso and four in Mato Grosso do Sul. The performance of the AquaCrop-OS model for the determination of soybean yield under current climatic conditions was evaluated. Simulations were performed to determine the best soybean sowing time for the future by the CMIP5 climate change GCM ensemble. To evaluate the results of the impact of climate on future soybean yield and on the yield of the best sowing time, a comparison was made with the current yield (1980-2015), according to simulations of the AquaCrop-OS model, in terms percentage relative change in productivity. The average performance of AquaCrop-OS for all municipalities, under rainfed conditions, by mean absolute error (EAM) and root mean square error (RMSE), was 0.72 ton.ha1 and 0.81 ton .ha-1, respectively. In the irrigated regime, the average performance of AquaCrop-OS for EAM and RMSE was 0.49 ton.ha-1 and 0.52 ton.ha-1 , respectively. Climate change will positively affect soybean crop productivity in the evaluated municipalities, mainly in irrigated planting under RCP 8.5, with an average increase in productivity of 18% by the end of the 21st century. According to projections, there will be, on average, in the municipalities of the states of Bahia, Goiás and Mato Grosso do Sul, a reduction in water demand for irrigation by the end of the 21st century. However, for municipalities in the state of Mato Grosso, there will be an increase in water demand. The late sowing time, compared to that adopted as the standard in this study, proved to be more viable to mitigate the effects of climate change.