Is there a relationship between water use efficiency and soil carbon dioxide emissions in soybean genotypes?

Selecting water-use-efficient (WUE) soybean genotypes is one of the main strategies of addressing climate change. Understanding soil carbon dioxide emissions is important for identifying production systems with plants that are more adapted to climate change, meeting Sustainable Development Goals 12 (responsible consumption and production) and 13 (climate action). This study aimed to verify whether there is a relationship between water use efficiency in soybean genotypes and soil carbon dioxide emissions (FCO₂). Twenty-five soybean genotypes were evaluated in a randomized block design with three replicates. At 60 days after crop emergence, the following variables were evaluated in each experimental unit: net photosynthesis (A, mmol CO₂ m^-2 s^-1), transpiration (E, mmol H₂O m^-2 s^-1), and FCO₂. The WUE was calculated by the ratio between A and E evaluated in three plants of each plot using an infrared gas analyzer (IRGA Li-6400XT) and was assessed using the portable EGM-5 system. Initially, the data were subjected to analysis of variance and grouping of means. Subsequently, the data were subjected to Pearson’s correlation. There was a significant difference between the soybean genotypes for the variables evaluated. The correlation between WUE and FCO₂ is of low magnitude. However, it is possible to select genotypes with higher WUE and lower FCO₂. The results reported here may guide selection strategies in soybean breeding programs.