Ammonium Soap As An Herbicide

By: , Certified Urban Agriculturist
A rubber gloved hand points a spray bottle at weeds
Image by Robin Gentry

Ammonium soap of fatty acids has been touted since 2006 as a safe, non-toxic herbicide. An ammonium nonanoate herbicide will control some weeds, brush, and even moss if used properly, and will not contaminate aquatic environments.

This is great news, because finding non-toxic alternatives to chemical herbicides can be challenging. Studies have shown that natural compounds such as acetic acid and fatty acids can be effective in controlling certain weeds.

What is Ammonium Nonanoate Herbicide?

Using an ammonium nonanoate safe preparation leaves little dangerous residue. It is a naturally occurring fatty acid found in some plants and animals. It is called a “soap salt” because fatty acids are part of the composition of soap. Ammonium nonanoate safe herbicides are non-systemic and have no soil activity. The soap gets into plant cells and reduces pH, which causes desiccation and eventually death of unwanted species. Application is topical, usually through spray. The active ingredient is a colorless or pale yellow liquid with a slight odor.

Using Ammonium Soap of Fatty Acids

This glyphosate alternative is non-systemic and has no soil activity. Therefore, it must cover the entire plant, since it does not produce results unless it has contact with plant tissue. It may be used in handheld, backpack, pump, and other spray methods. The product comes as a concentrate which must be diluted with water. Most suppliers recommend a dilution of 6.0 percent by weight. As with many other natural herbicides, reapplication is recommended on most pest plants.

Why Natural Herbicides?

Gardeners often have their own preferred natural herbicide. Some make up a mixture containing household and kitchen ingredients, others purchase a spray, dust, or granular preparation. Consistent among organic gardeners is the goal of finding a glyphosate alternative. Glyphosate has been shown to be toxic to humans and aquatic life, but one of the surfactants commonly used in products containing glyphosate, stays in an environment for a long time before degrading. This can be hazardous for certain wildlife.

Is This the Best Natural Herbicide?

Ammonium soap will work well on some plants, but not as well on others. In a comprehensive herbicide plan, it is best to use a combination of natural herbicides for the most effective control of pest plants. Using acetic acid, or horticultural grade vinegar, in combination with ammonium nonanoate is an excellent way to get broad spectrum control. Both work in a similar way and leave no damaging residue.

The EPA has concluded there is no health risk to humans, but the compound can cause eye, skin, and mucous membrane irritation. Long sleeves, eye protection, and avoiding inhaling the product are recommended.

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