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| Denitrification is a decomposition process that occurs under low O2 conditions.
When recognized as a decomposition process, it is obvious that the amount of easily decomposable organic matter in soil is a critical factor controlling denitrification rates.
Easily decomposable organic matter actually plays 2 important roles.
1) It promotes low oxygen conditions in soil by creating high biological oxygen demand i.e., aerobic microbes rapidly consume easily decomposable OM which results in rapid consumption of oxygen. In wet soils, oxygen replenishment is slow because diffusion of oxygen through water filled pores is much slower than through air filled pores.
2) anaerobic microbes eat easily decomposable OM and nitrate is consumed in place of oxygen
So why is oxygen consumed during aerobic decomposition and nitrate consumed during anaerobic decomposition?
In well aerated soils (i.e., soil pores with > ~10% oxygen), the chemistry of decomposition consists primarily of carbon atoms getting oxidized (i.e., giving up electrons) and oxygen atoms getting reduced (i.e., receiving the electrons given up by carbon atoms)
In poorly aerated soils, the chemistry of decomposition consists primarily of carbon atoms getting oxidized and nitrogen atoms getting reduced (i.e., receiving the electrons given up by carbon atoms).
Nitrogen atoms that are more oxidized (i.e., more depleted of electrons) are more inclined to receive electrons and the N atoms in nitrate are fully oxidized (i.e., they have given up all of their outer shell electrons) so the N atoms in nitrate ions become the main recipients of available electrons when oxygen supply is low.
Decomposition is faster at higher temps (~ 2x faster with each 10 degree celsius increase) so denitrification is faster.
For more info check out the document at the following link:
https://soils.ifas.ufl.edu/wetlands/publications/PDF-articles/283.An...
Joel
WIU Agriculture | |
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denitrification?
