Choose the Most Suitable Nitrogen Sources . It is important that nitrogen remain in the root zone long enough for it to be used by the growing crop. Regardless of its source, once nitrogen is in the plant it will not be lost and will not become a pollutant. The nitrogen source can affect nitrogen loss from soils for a few months after application. However, the nitrogen source has little effect on loss over the long run if the nitrogen stays in the soil.
Nitrification is a natural process in which ammonium is converted to nitrate by soil microorganisms.
Soil temperature, moisture, pH, and aeration determine the rate of nitrification. Under certain conditions, conversion occurs rapidly. In soils subject to leaching, inhibitors can be applied to slow nitrification and delay nitrogen losses. Slow-release nitrogen fertilizers can also reduce nitrogen losses. Some slow-release fertilizers can resist biological or chemical breakdown, and others have protective coatings.