Characterizing Brazilian soybean-growing regions by water deficit patterns

Abstract

The use of specific crop management in a growing region according to its climate can reduce the yield gap caused by water deficit, the main cause of soybean yield gap in Brazil. Therefore, this study aimed to characterize the Brazilian soybean-growing regions based on attainable yield and water deficit patterns. The attainable yields were estimated by the crop model DSSAT-CROPGRO-Soybean, considering six sowing dates, three soil types and 33 growing seasons (1980–2013), using gridded weather data with 453 locations. The homogenous regions were defined by the cluster analysis, based on attainable yield. The water deficit pattern (WDP) was identified by a simulated 5-day running average of water stress index (WSPD) during the growing seasons across different planting dates and soil types, using the cluster analysis for each homogenous region. The attainable yield varied considerably between environments, from 0 to 3400 kg ha−1. Ten environmental zones were obtained, where locations in the same zone indicated the same level and variability of the attainable yield across sowing dates, soils and growing seasons. The highest attainable yield (> 2800 kg ha−1) occurred in the central-western to northern regions (zones 1, 2 and 3), covering most soybean growing areas in Brazil. The lowest attainable yield was observed in the extreme South (zone 6) and East border (zone 7) (< 1170 kg ha−1). The highest attainable yield variability occurred in northern/northeastern (zones 4 and 5), eastern (zone 8) and southern (zones 9 and 10) regions. Three WDP were obtained in each environmental zone, which differed in frequency, level and moment of occurrence during the soybean growing season. Sowing dates and soil types contributed to defining the frequency of each WDP. The homogenous zones and WDP demonstrate that attainable yield and yield gap by water deficit can differ significantly across Brazilian soybean-growing regions. These patterns could be used to improve crop management, such as sowing dates, preferential soils, and irrigation requirements, as well as breeding strategies to deal with water deficit, namely deeper root systems, stomatal closure by decreased water content in the soil and drought tolerance of nitrogen fixation.