Ammonification is the production of ammonia from organic nitrogen-containing compounds by saprobionts. The ammonia dissolves in soil water to form ammonium ions (NH4+).Nitrogen in living organisms is locked up in organic molecules such as proteins, amino acids, nucleic acids and urea. When organisms die, or when animals produce faeces and urine, these compounds enter the soil. Plants cannot use most of them directly.Saprobionts (bacteria and fungi) break them down by extracellular digestion:1. They secrete enzymes, such as proteases, onto the dead material or waste.
2. Proteins are hydrolysed into amino acids, and nucleic acids into nucleotides.
3. The saprobionts absorb these products and use them in their own metabolism, releasing the excess nitrogen as ammonia.So ammonification returns nitrogen to the soil in an inorganic form. The ammonium ions can then be converted to nitrate ions by nitrifying bacteria (nitrification), or absorbed directly by some plants.
Example: Manure spread on a field contains undigested protein in faeces and urea in urine. Over the following weeks, saprobionts convert these into ammonium ions, which are then nitrified, providing nitrate for the crop. This is why manure acts as a slow-release natural fertiliser.Like all decomposition, ammonification is fastest in warm, moist soils where saprobionts' enzymes work quickly.
2. Proteins are hydrolysed into amino acids, and nucleic acids into nucleotides.
3. The saprobionts absorb these products and use them in their own metabolism, releasing the excess nitrogen as ammonia.So ammonification returns nitrogen to the soil in an inorganic form. The ammonium ions can then be converted to nitrate ions by nitrifying bacteria (nitrification), or absorbed directly by some plants.
Example: Manure spread on a field contains undigested protein in faeces and urea in urine. Over the following weeks, saprobionts convert these into ammonium ions, which are then nitrified, providing nitrate for the crop. This is why manure acts as a slow-release natural fertiliser.Like all decomposition, ammonification is fastest in warm, moist soils where saprobionts' enzymes work quickly.