How Does Ammonium Nitrate Affect Lawns?

What Is Ammonium Nitrate?

• Ammonium nitrate has a chemical formula of NH4NO3, and is sold as a 33-0-0 fertilizer, typically in quick-release formulations. There are a number of different production processes, all of which result in a whitish, granular, water-soluble product. Ammonium nitrate production utilizes ammonia to produce nitric acid, which is then reacted with more ammonia to produce ammonium nitrate. This process proceeds according to the following reaction: NH3 (g) + HNO3 9 (aq)' NH4NO3 .

  It is applied to landscapes in both liquid and granular forms, although the sale and use of ammonium nitrate has become increasingly restricted in recent years because of its high explosive potential.

Effect on Lawns

• Applying ammonium nitrate fertilizers to turf grasses supplies them with readily available nitrogen, which spurs vegetative growth. Applying nitrogen fertilizers results in increased greening, faster shoot growth, increased vegetative density and more vigorous root growth. Nitrogen fertilizers also help grasses increase their stored reserves of carbohydrates, as well as lowering their susceptibility to various turf grass diseases and disorders. Lawns with sufficient nitrogen exhibit increased heat, cold and drought tolerance as well, and they also recover more quickly from damage to roots or leaves.

Method of Application

• Most lawns require a nitrogen application rate of 1 pound per 1,000 square feet, and the amount necessary to achieve this rate can be determined easily with some simple calculations. To determine the weight of product necessary to supply 1 pound of nitrogen, divide the percentage of nitrogen listed on the fertilizer label by 100. The resulting figure is the amount of fertilizer necessary to supply 1 pound of actual nitrogen. This figure can be doubled for slow-release formulations.

Potential Drawbacks

• Ammonium nitrate is an excellent quick-release fertilizer, but there are a number of drawbacks to its use. Soils fertilized regularly with ammonium nitrate tend to become more acidic over time, with increased salt content. Although this can be remedied with applications of lime, significant soil degradation can occur over long periods of time. Ammonium nitrate fertilizers also leach readily from plants and soils, more so than other types of nitrogen fertilizers. This leaching contributes to nitrate pollution of ground and surface water sources. Ammonium nitrate also has a high explosive potential; it has been used to manufacture explosives used in several terrorist attacks, which has limited its availability. Locating large supplies is frequently problematic.