Evaluating the effects of foliar sulfur application timings on nutrient acquisition and soybean performance

Abstract

A reduction of atmospheric sulfur (S) deposition and increased S removal by high‐yielding crops in recent years have caused more frequent occurrences of S deficiency in crop‐producing regions of the United States. It is necessary to explore solutions for mitigating S deficiency to optimize soybean [ Glycine max (L.) Merr.] yield and seed quality. A field study was conducted from 2019 through 2021 at two locations in eastern South Dakota to determine the effect of foliar S application on soybean performance and nitrogen (N) and S accumulation at different growth stages. The study included 11 S application treatments of ammonium sulfate: five single foliar applications at rate of 5.6 kg S ha −1 , applied at V4, R2, R3, R4, and V4 + micronutrient; three treatments with multiple foliar applications at V4 + R2, V4 + R3, and R2 + R3 growth stages with each application at rate of 5.6 kg S ha −1 . Two preplant applications at rates of 5.6 and 11.2 kg S ha −1 and control were also included. Overall, multiple foliar applications increased S concentration in most recent mature leaves at R4 growth stage, S accumulation in leaves and stems at R6, S accumulation in stover at R8 growth stage. S applications decreased grain N:S ratio compared to control. However, S applications had no effect on S accumulation in pods and seeds, grain yield, grain protein, and oil content. The results suggest that foliar S application is not expected to be a widely recommended practice for soybean S management in eastern South Dakota.