Sulfur (S) is an essential macronutrient and a key component in essential amino acids, methionine and cysteine (MET+CYS) that are the building blocks of protein. For a number of reasons, including difficulties in analysis for S, soil testing and fertility management has largely ignored this essential plant macronutrient. Trials were carried out over three years to evaluate the role of S fertility on the yield, seed S content, S yield and seed MET+CYS content of three types of grain legumes: double crop soybeans (Glycine Max), full season soybeans, and common dry beans (Phaseolus vulgaris). Sulfur fertility management significantly increased yield, seed S content, S yield, and seed MET+CYS content on low S soils. Additionally, four soil extractions were evaluated as potential methods to improve S fertility recommendations. Calcium phosphate extractions more accurately identified sites that had a yield or seed s content response to applied S compared to Mehlich 3 and Calcium Chloride.