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CH3041
THE NITROGEN CYCLE
II
• N2 in the atmosphere is the largest
reservoir
(78% vol. of the atmosphere is N2).
• The triple bond in N2 is hard to break: Eact 950 kJ
/ mol. Only a few microorganisms can use N2 directly as a source of ‘N’.
• Microorganisms
convert N2 to the biotically available
forms of ‘N’ : NO3- and NH4+.
• NH4+is soluble and is retained in
soils.
• NO3- is soluble and is not retained in
soils.
• Anthropogenic
inputs of NO3- (fertilisers cattle ..) are
problematic as microorganisms break this down to toxic NO2-
in reducing conditions such as in digestive systems.
