Alternative sowing dates as a mitigation measure to reduce climate change impacts on soybean yields in southern Brazil

The climate and its variability is the main risk factor for the success of soybean crop in southern Brazil. Such aspect becomes even more important under the future climate scenarios, in which global warming is expected. Based on that, the objectives of this study were to identify the impacts of raising temperatures on soybean yields in southern Brazil and how management strategies represented by changing sowing dates could be able to mitigate them. The soybean yields for the present and future scenarios were estimated by the crop simulation model CROPGRO-Soybean calibrated for southern Brazil. The simulations were done for 13 locations distributed in the states of Parana, Santa Catarina and Rio Grande do Sul, considering climatic series of 31 years. The future climate scenarios were built based on downscaling temperature changes from ETA and PRECIS models for the periods: 2013-2043 (D25) and 2041-2071 (D55), without considering the increase in the atmospheric CO2 concentration. The soybean potential (Y-p) and attainable (Y-a) yields and their relationship (Y-a/Y-p) were estimated for all scenarios and used to determine the climatic risk for the crop. In order to investigate how to mitigate the global warming impacts on soybean yields, different sowing dates, two earlier and two later than the present recommendation, were simulated in the crop model and resulting yields were compared. In general, raising temperature will lead soybean crop in southern Brazil to lower yields, for both Y-p and Y-a, with higher impact on Y-a, independently of the climate model used. Also, the climatic risk for the crop will increase in the future climates scenarios. The strategy of changing the sowing date showed to be feasible to reduce the impacts of raising temperatures on soybean yields, but only when it is delayed in relation to the sowing period presently recommended for this crop in the region.