Does Ammonia Kill Grass?

Written by jennifer eblin
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Does Ammonia Kill Grass?
Ammonia is both helpful and dangerous to lawns. (Thinkstock/Comstock/Getty Images)

Ammonia is commonly used as a cleaning solution around the house. The liquid produces fumes that are potentially fatal to humans and animals. Different types of ammonia are also found in weed killers, grass killers and other products designed to kill pesky plants in your yard. Trace amounts of ammonia are even found in dog urine, which leaves brown patches and dead grass behind.

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Nonselective Killer

Ammonia is referred to as a nonselective killer because it kills anything it comes into contact with. Even when you use a plant killer that has a nozzle to direct the spray, you still risk killing grass and other plants. Ammonia is dangerous because it attaches to the roots of the plants or grass and not the surface like other plant killers. Once the substance reaches the roots, it kills the grass and keeps it from coming back in the future.


Ammonia is most effective as a grass killer when applied during warm periods, such as the spring or summer. It is also more effective when the area receives normal levels of rainfall. Ammonia is less effective during periods of drought and in cold weather.


Small amounts of ammonia are potentially beneficial to your lawn, including plants and grass. The ammonia acts as a nitrogen source for the plants, which promotes growth and greening. Ammonia is often listed in homemade fertiliser recipes. The grass cannot absorb all of the ammonia though, which can lead to certain problems. When the grass stops absorbing the ammonia, it sits on top of the grass and soaks into the surface, which causes browning to the grass and, if you use too much ammonia, it can also kill the grass.


The Garden Counselor lists a recipe that mixes ammonia with beer, mouthwash, soda pop and dish soap. You spray the solution on your lawn after mowing the grass, and apply more of the solution every few weeks. The belief is that, as the solution soaks into the ground, it reaches the roots of the grass and acts as a fertiliser. The solution supposedly kills germs and microbes that exist in the soil and keeps grass healthy. No research currently exists that supports ammonia as a fertiliser. You must walk a fine line between using the right ratio of ammonia and helping the plant or using too much ammonia. A high concentration of ammonia applied to the grass will kill it.

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