Geographical zoning of soybean yield adaptation according to relative maturity in Brazil

Resumo

Brazil is the largest soybean producer, representing about 40% of world production. Soybean fields span all country regions, resulting in high environmental diversity for cultivation. The wide adoption of early-maturity cultivars and intensified cropping systems has recently introduced significant challenges in selecting the most well-adapted cultivars. In this study, we aimed to map soybean yield adaptation geographically, according to relative maturity (RM) groups, to increase assertiveness in cultivar development and recommendation. Data from yield trials of 175 locations were used, covering latitudes from 7ºS to 33ºS. The trials were conducted from 2014/2015 to 2017/2018 crop seasons. Altogether, 159 cultivars with different RM were evaluated in each location. The grain yield was adjusted using the linear mixed model to identify the most adapted RM range in each location. Subsequently, the regression kriging method was performed to spatialize this optimized RM, considering the latitude, longitude and elevation as predictors. We concluded that under Brazilian soybean growing conditions, cultivars with RM from 5.5 to 6.4 are best adapted in the subtropical region, and, in the subtropical/tropical transition, are those with RM from 6.5 to 6.9. In the tropical region, predominantly, cultivars with RM from 7.5 to 8.4 are best adapted. The adaptation of late-maturity cultivars with RM from 8.5 to 9.4 has been restricted to the northernmost regions. Latitude and elevation are key factors in defining soybean yield adaptation, with elevation promoting slight deflections in adaptation zones, favoring earlier cultivars. In contrast, longitude does not show significant effect on adaptation to these conditions.