Sulfur fertilization alters soybean seed protein in one of two test environments in the Southeast U.S.

Authors: EPIE, KENEDY - Former ARS Employee; BAUER, PHILLIP - Retired ARS Employee; Stone, Kenneth; Locke, Anna

Submitted to: Journal of Plant Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/13/2025
Publication Date: 7/6/2025
Citation: Epie, K.E., Bauer, P.J., Stone, K.C., Locke, A.M. 2025. Sulfur fertilization alters soybean seed protein in one of two test environments in the Southeast U.S.. Journal of Plant Nutrition. https://doi.org/10.1080/01904167.2025.2522253.
DOI: https://doi.org/10.1080/01904167.2025.2522253

Interpretive Summary: Increasing soybean seed protein concentration is an important goal for farmers and end-users of soybean meal. In some regions, sulfur fertilization has been shown to affect seed protein concentration, but the effect is highly variable among environments. Southeast US soybean growers need region-specific information to inform management decisions. Field experiments were conducted to measure the response of seed composition to soil and foliar sulfur applications. Foliar sulfur application increased total protein production per land area in one of six environments tested but reduced it in another, and seed protein concentration was not affected. Soil sulfur application at planting increased seed protein concentration in one of two environments tested. Foliar sulfur application also affected the percentage of seed nitrogen derived from biological nitrogen fixation, but the effect varied among environments. These results suggest that sulfur fertilization may not improve seed composition in most environments in the Southeast US, but the effect of sulfur application on soybean nitrogen metabolism requires further study.

Technical Abstract: Soybean seed protein concentration has declined over decades of yield-focused breeding, and new management strategies are desired to improve seed composition for end users. Sulfur and nitrogen metabolism are linked, and substantial quantities of each are required for seed storage protein production. Foliar sulfur application at anthesis increased seed yield, as well as total protein and oil produced per area, in one of six environments tested and reduced the same parameters in another environment. Foliar sulfur application also affected the percentage of nitrogen derived from fixation in seeds, but not in leaves. In a separate experiment, sulfur applied at planting did not affect total protein production but increased seed protein concentration in one of two environments. The highly variable impacts on yield and seed composition suggest that sulfur application may not be a practical quality-improvement strategy for growers in the Southeast U.S., and these results highlight the complex interdependency between sulfur and nitrogen metabolism in soybean.