Here is part of what I have been reading
.
Many soil bacteria process nitrogen in organic substrates, but only nitrogen fixing bacteria can process the nitrogen in the atmosphere into a form (fixed nitrogen) that plants can use. Nitrogen fixation occurs because these specific bacteria produce the nitrogenase enzyme. Nitrogen fixing bacteria are generally widely available in most soil types (both free living soil species and bacteria species dependent on a plant host). Free living species generally only comprise a very small percentage of the total microbial population and are often bacteria strains with low nitrogen fixing ability (Dick, W., 2009).
Nitrification is a process where nitrifying bacteria convert ammonia (NH4+) to nitrite (NO2-) and then to nitrate (NO3-). Bacteria and fungi are typically consumed by protozoa and nematodes and the microbial wastes they excrete is ammonia (NH4+) which is plant available nitrogen. Nitrite bacteria (Nitrosomonas spp.) convert the ammonia into nitrites (NO2-) and nitrate bacteria (Nitrobacter spp.) may then convert the nitrites (NO2-) to nitrates (NO3-). Nitrifying bacteria prefer alkaline soil conditions or a pH above 7 (Lowenfels & Lewis, 2006). Both nitrate and ammonia are plant available forms of nitrogen; however, most plants prefer ammonia because the nitrate has to be converted to ammonia in the plant cell in order to form amino acids.
Denitrifying bacteria allow nitrate (NO3-) to be converted to nitrous oxide (N2O) or dinitrogen (N2) (atmospheric nitrogen). For denitrification to occur, a lack of oxygen or anaerobic conditions must occur to allow the bacteria to cleave off the oxygen. These conditions are common in ponded or saturated fields, compacted fields, or deep inside the microaggregates of soil where oxygen is limited. Denitrifying bacteria decrease the nitrogen fertility of soils by allowing the nitrogen to escape back into the atmosphere. On a saturated clay soil, as much as 40 to 60 percent of the soil nitrogen may be lost by denitrification to the atmosphere (Dick, W., 2009).
.
Many soil bacteria process nitrogen in organic substrates, but only nitrogen fixing bacteria can process the nitrogen in the atmosphere into a form (fixed nitrogen) that plants can use. Nitrogen fixation occurs because these specific bacteria produce the nitrogenase enzyme. Nitrogen fixing bacteria are generally widely available in most soil types (both free living soil species and bacteria species dependent on a plant host). Free living species generally only comprise a very small percentage of the total microbial population and are often bacteria strains with low nitrogen fixing ability (Dick, W., 2009).
Nitrification is a process where nitrifying bacteria convert ammonia (NH4+) to nitrite (NO2-) and then to nitrate (NO3-). Bacteria and fungi are typically consumed by protozoa and nematodes and the microbial wastes they excrete is ammonia (NH4+) which is plant available nitrogen. Nitrite bacteria (Nitrosomonas spp.) convert the ammonia into nitrites (NO2-) and nitrate bacteria (Nitrobacter spp.) may then convert the nitrites (NO2-) to nitrates (NO3-). Nitrifying bacteria prefer alkaline soil conditions or a pH above 7 (Lowenfels & Lewis, 2006). Both nitrate and ammonia are plant available forms of nitrogen; however, most plants prefer ammonia because the nitrate has to be converted to ammonia in the plant cell in order to form amino acids.
Denitrifying bacteria allow nitrate (NO3-) to be converted to nitrous oxide (N2O) or dinitrogen (N2) (atmospheric nitrogen). For denitrification to occur, a lack of oxygen or anaerobic conditions must occur to allow the bacteria to cleave off the oxygen. These conditions are common in ponded or saturated fields, compacted fields, or deep inside the microaggregates of soil where oxygen is limited. Denitrifying bacteria decrease the nitrogen fertility of soils by allowing the nitrogen to escape back into the atmosphere. On a saturated clay soil, as much as 40 to 60 percent of the soil nitrogen may be lost by denitrification to the atmosphere (Dick, W., 2009).
