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Abstract

Context and objective: Soybean production in South Africa is increasingly threatened by climate change; but the historical interplay between changing climate and genetic improvement on yield remains unexplored. This study assessed the historical influence of climate change and genetic trait improvement on soybean yield from 1998 to 2022 across four different South African localities: Bethlehem, Delmas, Brits and Potchefstroom. Methods: Seasonal climate trends were evaluated using the non–parametric tests, yield anomalies were quantified using detrended standardized residuals, and the effects of rainfall and temperature on yield were analyzed through Bayesian hierarchical modelling. The contribution of genetic improvement to yield gains was evaluated using structural equation modelling (SEM). Results and Conclusions: Results evealed generally decreasing seasonal rainfall trends, significant in Bethlehem and significant increases in the maximum temperature across all localities and seasons. Minimum temperature significantly increased in Delmas, Brits and Potchefstroom across all seasons, with non–significant trends in Bethlehem. Negative yield anomalies occurred at all localities, with extreme losses noted in Delmas and Potchefstroom during the 2006/07 season. Bayesian modelling showed credible positive effects of rainfall on soybean yield in Delmas and Brits across both vegetative and reproductive phases. In Potchefstroom, a credible positive effect was noted only during the vegetative phase while in Bethlehem during reproductive phase. Credible negative rainfall effects occurred in Bethlehem across both overall season and vegetative phase, and in Potchefstroom and Delmas during the overall season. Uncertain negative effects on yield were noted in the reproductive period in Potchefstroom and Brits during the overall season. Maximum temperature exerted a consistently credible negative impact on yield across all localities, and minimum temperature had credible positive effects on yield in Delmas, Brits and Potchefstroom, but weak and uncertain effects in Bethlehem. Despite these climatic stresses, yield gains were observed over time, with Potchefstroom showing the largest increase (31.4 kg ha–1 yr–1). Genetic improvements in seed mass, seed number and plant height were the major drivers of yield gains across all localities, with days after planting (DAP) to harvest maturity also contributing to yield gain in Brits. Overall, soybean yield gains have been sustained despite increasing climate stress, highlighting the importance of climate–smart breeding strategies and location–specific agronomic management.

Document Type

Article

Publication Date

8-1-2026

Notes/Citation Information

Publisher Copyright: © 2026 The Authors

Digital Object Identifier (DOI)

10.1016/j.fcr.2026.110612

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