Concept:Nitrification is the process by which ammonium compounds are oxidised into nitrites and then into nitrates by soil bacteria.
Explanation:First, bacteria such as
Nitrosomonas convert ammonium salts into nitrites.
Then, bacteria such as
Nitrobacter convert nitrites into nitrates.
Thus, the conversion of ammonium salts into nitrates is a two-step biological process.
This process is called nitrification.
It is distinct from putrefaction, denitrification, and nitrogen fixation.
Putrefaction is the decomposition of organic matter.
Denitrification converts nitrates back into nitrogen gas.
Fixation converts atmospheric nitrogen into ammonia or related compounds.
Hence, the correct option is nitrification.
Answer:D. nitrification