Assessing environmental and management factors that drive soybean yield gaps in Brazil

Brazil is the world's largest producer and exporter of soybeans (Glycine max L. Merr.). Assessing yield gaps (Yg) is essential for improving resource use efficiency and guiding farmers' management strategies. The objective of this study was to estimate soybean yield potential (Yp), water-limited yields (Yw), and Yg based on water and agricultural practices across Brazil's five soybean macroregions. We have quantified yield losses due to delayed sowing and evaluated interannual yield variability caused by environmental and climatic factors. The results revealed that the southern regions had the highest Yp values but also the largest Yg values, which were strongly influenced by climatic factors. In contrast, the Brazilian Midwest had the lowest Yp yet minimal water-related Yg, with relatively stable yields over time; here, Yg were primarily due to crop management rather than climatic constraints. In northern macroregions, lower Yp was observed with moderate climatic influences. Delayed sowing reduced Yp across all macroregions, with the greatest losses occurring in regions with initially high Yp, particularly in the south. Each macroregion has unique environmental conditions that lead to different patterns of Yp, Ya (actual yield), and Yw. In the southern macroregions, Yg are primarily due to water constraints, indicating potential benefits of irrigation, while the Midwest, which has the lowest Yg, improved crop management practices offer the most significant opportunity for yield gains.