The three main sources of NH 3 on farms are animal wastes, fertilizers, and crop residues. As a result, a large proportion of the N in manure can be lost as NH 3 soon after excretion. Losses of N during storage of manure can also be high, depending on method of storage. The differences reflect the degree of exposure to air and the amount of water and acid present. Some NH 3 is also released when manure is applied to land, particularly if a slurry is sprayed into the air.
Most loss occurs shortly after application.
Figure 33 Pattern of NH 3 loss from manure applied to the surface of soil. Another potential source of NH 3 is fertilizer. Urea fertilizer, like the urea in livestock manure, quickly converts to NH 3 and CO 2 after it is applied. If the fertilizer is not mixed into the soil, large amounts of NH 3 can be released to the atmosphere. A third possible source of NH 3 from farms is crop residues.