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THE EFFECT OF ADDED NITROGEN ON THE RATE OF DECOMPOSITION OF ORGANIC MATTER
Author(s) -
FOG KÅRE
Publication year - 1988
Publication title -
biological reviews
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.993
H-Index - 165
eISSN - 1469-185X
pISSN - 1464-7931
DOI - 10.1111/j.1469-185x.1988.tb00725.x
Subject(s) - chemistry , humus , decomposition , organic matter , mineralization (soil science) , straw , nitrogen , browning , ammonia , decomposer , metabolite , microorganism , food science , environmental chemistry , organic chemistry , biochemistry , bacteria , biology , ecosystem , inorganic chemistry , ecology , genetics , soil water
Summary (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.