Fig. 1: Brazilian soybean breadbaskets, agricultural dependency on rainfall, and growing season rainfall variability.

a Soybean production (tons) in Brazil based on the year 2000, and calculated as yield in tons per hectare⁶⁹ multiplied by harvest area in hectares⁴⁹. The two contours in the figure, green and blue, enclose the two cropland regions studied: the southern Amazon and Cerrado region (ACR) and the southern Brazilian region (SBR). The pie chart in the lower right corner shows the relative contribution of each of them to the total soybean production of Brazil. The background map shows the elevation of South America. b Time series of rainfall over the growing period (from October to April) for both ACR (green) and SBR (blue) from 1982 to 2018. The growing-season precipitation was calculated as an area-weighted average using the Multi-Source Weighted-Ensemble Precipitation (MSWEP⁶⁵). In the upper left corner, we show the long-term trend of rainfall (lines), calculated as the slope of a linear regression (S), and the p value associated with it. c Relationship between soybean yield and growing season rainfall over the rainfed breadbaskets. In the upper left corner, we show the Pearson’s correlation between the growing-season rainfall and relative soybean yield anomaly (Y_p) that is calculated by removing the long-term trend (for details, see Methods).