Lawn Fertilizers & Ammonia

How Ammonia Works

• Nitrogen is a critical element for plant growth. Starve a plant of nitrogen, and it will rapidly lose health and eventually die. Plants cannot use raw nitrogen, though. It must first be converted by nitrogen-fixing bacteria to ammonia, which in turn is converted into nitrite and nitrate ions. These ions are taken up by the roots and are used to provide energy to stems and leaves. The nitrogen left in the soil is reworked by other bacteria and is eventually converted back to gas, which escapes to the air. Once this process was scientifically understood, the simple question was, "Why not just put a form of ammonia into the soil to take a shortcut?"

Types of Ammonia

• Ammonium nitrate and ammonium sulfate have traditionally been the two most common forms of nitrogen fertilizer for plants. They are considered quick-release fertilizers because the chemicals are readily available for plant use. Urea, or natural fertilizer from animals, has overtaken ammonium nitrate in usage as a fertilizer, according to the experts at the University of Minnesota. Containing 46 percent nitrogen, the compound is less explosive, has fewer pollutants and is more effective than other forms of ammonia.

Burning the Grass

• All fertilizers are salty, even natural ones. If the ammonia-based fertilizer is overused, it may harm the grass by drawing water out of the grass roots. This will cause the grass to die. You can see how this works when a dog is allowed to urinate on the lawn. A dog with low nitrogen in its urine will cause the grass to lushly grow in that spot more than in the surrounding area, but a dog with high-nitrogen urine will create a dead, yellow spot.

Slow-release Ammonia

• Nitrogen that converts to ammonia over a long period is considered a slow-release fertilizer. Small sulfur- or polymer-coated capsules filled with urea gradually lose their coating and become available to the grass. By coating the capsules in a gradient from thin to thick, the beneficial effect can last over several months. Organic fertilizers such as compost are slow-release as well. Composted manure is slow-release, but raw manure is considered a fast-release fertilizer.