Decomposition of Sewage Sludges in Soil as Affected by their Organic Matter Composition

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Abstract
The rate of mineralization of C and N in a Light-colored Andosol amended with six different sewage sIudges was studied during a 8-week incubation period at 28°C in order to determine how the chemical composition of the added sludges influences their decomposition. Chemical analyses of the sludges showed that the composition of the organic matter (i.e. lipid. water-soluble sugar, hemicellulose, cellulose, crude protein, and lignin) and of organic nitrogen (i.e. amino acid-N, hexosamine-N, and unidentified-N) was similar among the sludges while the amount of the total organic matter varied widely. The mineralization rate of sludge organic C was related negatively to the sum of the inorganic matter and lignin (unextractable organic matter) contents of the sludge. The mineralization rate of sludge organic N was related to the crude protein content of the total sludge organic matter.