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THE EFFECT OF ADDED NITROGEN ON THE RATE OF DECOMPOSITION OF ORGANIC MATTER
Article first published online: 21 JAN 2008
Volume 63, Issue 3, pages 433–462, August 1988
How to Cite
FOG, K. (1988), THE EFFECT OF ADDED NITROGEN ON THE RATE OF DECOMPOSITION OF ORGANIC MATTER. Biological Reviews, 63: 433–462. doi: 10.1111/j.1469-185X.1988.tb00725.x
- Issue published online: 21 JAN 2008
- Article first published online: 21 JAN 2008
- Received 2 November 1987, revised 11 April 1988
(1) N added to decomposing organic matter often has no effect or a negative effect on microbial activity, at least in the long term. More than 60 papers are cited in support of this statement.
(2) The negative effect of N is mainly found with recalcitrant organic matter with a high C/N ratio (straw, wood, etc.), whereas a positive effect of N is common for easily degradable organic material with low C/N ratio.
(3) The negative effect of N could be explained by: (i) N disturbs the outcome of competition between potent and less potent decomposers; (ii) through ‘ammonia metabolite repression’, N blocks production of certain enzymes, at least in basidiomycetes, and enhances breakdown of the most available cellulose, whereby recalcitrant lignocellulose accumulates; (iii) amino compounds condense with polyphenols and other decomposition products, forming ‘browning precursors’ which are toxic or inhibitory.
(4) The effect of adding N may depend on the microflora present.
(5) There are indications that some microorganisms have a ‘luxury uptake’ of N when it is present in sufficient amounts, thereby delaying N mineralization.
(6) The addition of N seems to increase the formation of water-soluble, brown, recalcitrant compounds, but to decrease the amount of humus formed.