When to Apply Ammonia Sulfate to the Lawn?

Updated March 23, 2017

Soils generally lack the complete nutrients required for a strong, attractive lawn. Healthy growth is dependent upon 18 elements, according to soil scientists at the University of Minnesota Extension. Chief among these is nitrogen, which is paramount in creating the lush, green colour homeowners work so hard to achieve. Just as too little nitrogen can stunt the grass's growth and leave it susceptible to weeds and disease, excess nitrogen results in a reduction in root growth and susceptibility to certain diseases. Applied at the proper rate, at the appropriate time, ammonium sulphate provides the lawn the nitrogen it requires.


Ammonium sulphate is produced by combining ammonia with sulphuric acid and its final form, as a fertiliser, is a white crystalline, much like a salt. It contains 20 to 21 per cent nitrogen. It is easy to handle and store although it clumps when conditions are wet or humid. Over time, ammonium sulphate 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 sulphate.


Although there are better choices for starter fertilisers, ammonium sulphate 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 sulphate does not contain. Established lawns require two to four applications per season. Make the first application when the soil warms to 10 degrees Celsius. Reapply every four to six weeks, spring through fall. Apply the fertiliser during dry weather, when the grass is dry, and the temperature is below 26.7 degrees Celsius.


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


Whether you use a drop or rotary spreader, the ammonium sulphate package lists calibration rates for different spreaders. Use the rate suggested for your brand of spreader and walk the lawn, spreading the ammonium sulphate evenly. Turf specialists with the University of Minnesota Extension suggest applying the fertiliser 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.

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About the Author

Based in the American Southwest, Bridget Kelly has been writing about gardening and real estate since 2005. Her articles have appeared at,,, RE/,,, and in "Chicago Agent" magazine, to name a few. She holds a Bachelor of Arts in English with a concentration in creative writing.