What Is the Fate of Ammonia in Soil?

Ammonia

• A special plow applies fertilizer ammonia to agricultural soils. Metal tines open the soil, allowing the allowing liquid ammonia insertion. After it enters the soil, ammonia binds with tiny clay and organic matter particles. Bacteria convert ammonia to nitrate in time. During the conversion, three hydrogen ions are lost into the soil solution, which makes the soil more acidic. Nitrate is a usable form of nitrogen for plants, but it is also water soluble and easily leached from the soil.

Plant Use

• Plants take up ammonia mineralized to soil particles and converted nitrate through their roots. In nature, much nitrogen taken up by plants returns to the soil when they die. As crops are harvested, nitrogen is taken from the cycle and must be replaced.

Nitrogen Loss

• When ammonia converts to nitrate, rain or irrigation water dissolves it and it drains from the soil. When using ammonia as a fertilizer, test the soil first for nutrient levels. Add as much ammonia as recommended by the soil-testing lab. The recommendation accounts for ammonia likely to convert to nitrate and be leached from the soil. Overfertilizing is expensive, caused pollution and harms crops.

Pollution

• Nitrates from ammonia fertilizers leached from the soil can pollute groundwater. Nitrogen pollution causes blue baby syndrome. Soils with a high percentage of clay are less permeable to water and may be subjected to erosion. Surface soil erosion carries away enough nitrates and contaminates groundwater.