Nitrification, for example, occurs very slowly at cold temperatures and ceases once the temperature declines below freezing (Figure 5.3). Mineralization and nitrification are influenced by environmental factors that affect biological activity such as temperature, moisture, aeration, pH, and so forth. This step rapidly follows ammonium conversion to nitrite, and consequently nitrite concentrations are normally low in soils. The second step of nitrification occurs through Nitrobacter species, which convert nitrite to nitrate. Nitrification inhibitors, such as nitrapyrin (N-Serve R) or dicyandiamide (DCD), interfere with the function of these bacteria, blocking ammonium conversion to leachable nitrate. Nitrosomonas (obligate autotrophic bacteria) convert ammonium to nitrite. Microbial activity is also responsible for the two steps of nitrification. Again, microorganisms (primarily autotrophic) accomplish this action.Īmmonification: R-NH 2 + H 2O -> NH 3 + R-OH

For example, urea is an amide added directly to soil either in animal urine or as commercial fertilizer.Īminization: Proteins -> R + -NH 2 + R-OHĪmmonificationis the second step of mineralization in which amino (NH 2) groups are converted to ammonium. Autotrophic microorganisms can derive energy from the oxidation of inorganic elements or compounds such as iron (Fe), sulfur (S), ammonium, nitrite, or from radiant energy.) They derive their carbon from carbon dioxide (CO 2). (Heterotrophic microorganisms require preformed organic compounds as sources of carbon and energy. The first step of mineralization is called aminization, in which microorganisms (primarily heterotrophs) break down complex proteins to simpler amino acids, amides, and amines.

Mineralization occurs in soil as microorganisms convert organic nitrogen to inorganic forms. Once nitrogen is fixed, it is subject to several chemical reactions which can convert it to different organic or inorganic forms.

What is inorganic matter