When to Apply Ammonia Sulfate to the Lawn?

Characteristics

• Ammonium sulfate is produced by combining ammonia with sulfuric acid and its final form, as a fertilizer, is a white crystalline, much like a salt. It contains 20 to 21 percent nitrogen. It is easy to handle and store although it clumps when conditions are wet or humid. Over time, ammonium sulfate may acidify the soil. Although the product is not considered toxic, it may abrade the eyes upon contact and may cause mild dermatitis in sensitive individuals. Wear gloves and eye protection when working with ammonium sulfate.

Timing

• Although there are better choices for starter fertilizers, ammonium sulfate may be added to the soil before sowing the grass seed as long as it is mixed deeply into the soil. Grass seeds require phosphate, which ammonium sulfate does not contain. Established lawns require two to four applications per season. Make the first application when the soil warms to 50 degrees Fahrenheit. Reapply every four to six weeks, spring through fall. Apply the fertilizer during dry weather, when the grass is dry, and the temperature is below 80 degrees Fahrenheit.

Rate

• Ammonium sulfate is a quick-release type of nitrogen. These fertilizers have a tendency to burn the grass if applied at too high of a rate. Slow-release nitrogen fertilizers, such as sulfur-coated urea, may be applied at high rates without the worry of fertilizer burn. Generally, ammonium sulfate is applied at a rate of 1 pound per 1,000 square feet, per application.

Application

• Whether you use a drop or rotary spreader, the ammonium sulfate package lists calibration rates for different spreaders. Use the rate suggested for your brand of spreader and walk the lawn, spreading the ammonium sulfate evenly. Turf specialists with the University of Minnesota Extension suggest applying the fertilizer in a checkerboard pattern to assure even coverage. Water the product into the top 6 inches of the lawn to distribute it evenly among the roots.