Deteriorating weed control and variable weather portends greater soybean yield losses in the future

Authors: LANDAU, CHRISTOPHER - University Of Illinois; HAGER, AARON - University Of Illinois; Williams, Martin

Submitted to: Science of the Total Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/19/2022
Publication Date: 3/29/2022
Citation: Landau, C.A., Hager, A.G., Williams II, M.M. 2022. Deteriorating weed control and variable weather portends greater soybean yield losses in the future. Science of the Total Environment. 830. Article 154764. https://doi.org/10.1016/j.scitotenv.2022.154764.
DOI: https://doi.org/10.1016/j.scitotenv.2022.154764

Interpretive Summary: Soybean yield projections due to climate change ignore the fact that weeds are present in every field, are becoming more difficult to control, and are an additional source of crop stress. We conducted research to examine the issue of deteriorating weed control and adverse weather on soybean yield. We found that lower rainfall or higher temperatures during soybean seed fill exacerbated soybean yield loss due to incomplete weed control. This work shows soybean yield projections are likely overestimates, unless future weed management systems are transformed in a way that achieve near-perfect weed control.

Technical Abstract: Anthropogenic climate change continues to present challenges to soybean production. Since the 1950’s in the Midwest, carbon emissions have increased, temperatures have risen, and rainfall has become more variable. These climate trends are predicted to continue throughout the 21st century. Both variable weather and weed interference influence crop performance; however, their combined effects on soybean yield is poorly understood. The objective of this research was to determine the most important relationships among weed control, weather variability, and crop management on soybean yield loss due to weeds. A database of 106 individual herbicide evaluation trials spanning 26 years was used to model the relationship between weed control and soybean yield loss due to weeds. The database was analyzed using regression, random forests (RF), and classification and regression tree (CART) analyses. When weeds were not controlled, an average yield loss of 49% was observed; however, yield loss attenuated as percent weed control increased. RF and CART confirmed late-season weed control was as a major driver of soybean yield loss, with yield losses increasing as weed control deteriorated. Additionally, a linkage between inadequate weed control and warmer, drier conditions was identified. Low rainfall and higher average air temperatures during soybean seed filling exacerbated yield losses due to poorly controlled weeds. Since the Midwest is heading towards drier, warmer conditions, the risk of soybean yield loss will increase without significant improvements in weed management systems.