Ammonia in Soils

Ammonia plays a very important role in soil. Ammonia not only acts as a source of nitrogen in the soil, but it is also capable of changing the pH and acidity levels of the soil. The more ammonia you add, the more acidic your soil becomes. As such, ammonia can readily be found in commercial fertilizers.

What is Ammonia

There are three atoms of hydrogen and one atom of nitrogen in each atom of ammonia. This substance is a colorless liquid or gas with a distinct odor. Ammonia is commonly introduced to soil through animal manure or through the application of commercial fertilizers containing ammonia.

Ammonia's Reaction in Soil

When ammonia comes in contact with soil, it binds to the positive charged matter in the soil and eventually becomes nitrate. The speed of conversion from ammonia to nitrate depends upon the temperature of the soil. This nitrogen acts as a nutrient for plants, animals and humans.

Ammonia & Soil pH

During the process of converting ammonia to nitrogen, three hydrogen ions are released and two oxygen ions are added. The extra oxygens serve as the air in the soil. The extra hydrogen released during the conversion become the "acid" in the soil. If lime is present in the soil, it neutralizes the extra hydrogen by turning it into carbon dioxide.

Acidic Soil

If the hydrogen is not neutralized by lime, the result is changing the pH of the soil to that of an acidic soil. If the pH of the soil is less than 7, it is considered acidic. While there are many contributing factors to the pH of the soil, the application of an ammonia fertilizer can change the pH of the soil most quickly.

Acidic Soils & the Effect on Plants

In slightly acidic soils (a pH of 6 or 7) the plants are readily able to absorb the soluble nutrients. In highly acidic soils, bacteria is less able to decompose organic matter, thus preventing the matter from breaking down. The result is soil with a high content of organic matter. This high content of organic matter means that nutrients such as nitrogen are tied up and not able to be released to the plants that need them.

References

• Washington State University: Soil pH, Fertilizers and Lime
• Illinois Department of Public Health: Ammonia
• Iowa State University: Nitrogen Fertilizers and Soil pH