Do hard red spring wheat varieties vary in their response to Sulfur?

Sulfur is increasingly reported as deficient in many crops in the Upper Midwest of the United States. The objectives of this study were to determine if hard red spring wheat (HRSW) (Triticum aestivum L. em thell.) varieties vary in response to S and to determine if plant tissue analysis can predict grain yield. Two studies were established in Minnesota. Study 1 compared two sources of S applied at four rates with and without in-sea-son S. Study 2 compared the response of six HRSW varieties to three rates of S (0, 8, and 16 kg S ha^–1). Spring wheat grain yield and protein concentration were not affected by S rate, source, or timing with soil organic matter (SOM) >20 g kg^–1. For locations with SOM <20 g kg^–1, which were all sandy and irrigated, 8 kg S ha^–1 maximized grain yield and protein concentration. Flag leaf S concentration varied among varieties separately from S rate applied. Wheat grain yield decreased when flag leaf S concentration was <4.1 g S kg^–1, and grain yield responses were likely with concentrations <2.8 g S kg^–1. There were negative relationships between tissue N/S concentration ratios and grain yield, but critical N/S concentration could not be determined. Application of S for HRSW should be targeted to soils with SOM <20 g kg^–1 (0–15 cm). Sulfur rates sufficient to increase yield will result in an optimal protein concentration, and guidelines should not be varied based on the variety grown.