Ammonium sulfate [(NH₄)₂ SO₄] was one of the first and most widely used nitrogen (N) fertilizers for crop production. It’s now less common but especially valuable where both N and sulfur (S) are required. Its high solubility provides versatility for a number of agricultural applications. Growers apply ammonium sulfate primarily where they need supplemental N and S to meet the nutritional requirement of growing plants. It provides an excellent source of S, which supports or drives numerous essential plant functions, including protein synthesis.