Ammonium sulfate is a water soluble fertilizer providing 21 percent nitrogen by weight and 24 percent sulfur. The guaranteed analysis is 21-0-0+24(S). It can be applied to lawns as a top dressing of nitrogen and sulfur with a broadcast or drop-type spreader. In areas with high pH soils, the sulfur in ammonium sulfate helps lower soil pH levels. As with other fertilizers, water the treated area well after each application.
Ammonium sulfate provides lawns with readily available nitrogen and sulfur. It helps lawns green up quickly, helps in cold soils, and is relatively inexpensive. If too much ammonium sulfate is applied, an undesirable large amount of growth may result. Grass is more likely to be burned with applications of ammonium sulfate than with slow release products, and there is a greater likelihood of it leaching off the places where it is applied. When using ammonium sulfate, monitor soil pH and add lime as needed.
Use ammonium sulfate when a lawn grass with high nitrogen requirements (such as Bermuda grass) needs a boost of nitrogen during the late spring or late summer (not late fall) grass growing season. In the spring, the Texas A&M University Extension Service advises there is usually enough nitrogen for adequate growth through several mowings. Apply a complete fertilizer first, then ammonium sulfate can be applied in 45 to 60 day intervals. The service recommends slow release fertilizers during the middle of the summer. Avoid ammonium sulfate in the fall to decrease the likelihood of diseases and winter kill.
Ammonium sulfate has several benefits in addition to providing quick grass growth and reducing soil pH levels in alkaline lawns. It is easy to store and does not melt in high humidity like ammonium nitrate, another high nitrogen fertilizer. It is produced domestically as a by-product of the steel-making industry and is not subject to price fluctuations of natural gas, a chief component in anhydrous ammonia used to make ammonium nitrate. Ammonium sulfate is also nonflammable.
Of the nutrients grass receives from the soil, more nitrogen is required than any other applied fertilizer. It is also the product that burns lawns when applied at excessive rates. Without a soil test, the Clemson University Extension Service recommends applying 1 lb. of nitrogen per 1,000 square feet for a high maintenance lawn and 1/2 lb. of nitrogen per 1,000 square feet on a low maintenance lawn. For ammonium sulfate, 5 lbs. of ammonium sulfate provide 1 lb. of nitrogen per 1,000 square feet, while 2.5 lbs. provide 1/2 lb. of nitrogen per 1,000 square feet.
If ingested in large amounts, a material data safety sheet on ammonium nitrate recommends drinking two to three glasses of water, inducing vomiting and calling a doctor. If ammonium nitrate comes in contact with the eyes, slight discomfort is possible. Prolonged contact with the skin could cause slight abrasions. As with most fertilizers, especially high nitrogen ones, keep ammonium sulfate out of waterways and bodies of water. The fertilizer has shown it can promote algae growth.