CHANGE IN N-FRACTIONS DURING COMPOSTING OF WHEAT-STRAW

The composting process found in real compost heaps was simulated in the laboratory with three treatments, nil, and urea, and cyanamide additions. Total N was separated into hydrolysable, amino acid, and amino sugar N. These fractions were related to counts of viable bacteria and spore-forming bacteria. The content of amino acid N and amino sugar N increased in all three treatments. The ratios of amino acid to amino sugar C and glucosamine to galactosamine decreased in all three treatments during composting of wheat straw. The increased contents of the N components were all significantly correlated with the number of spore-forming bacteria but not with viable bacterial counts. The closest correlation was found between spores and galactosamine. Amounts equivalent to 74% (urea treatment) or 48% (cyanamide treatment) of the added N were lost, mainly in the period after the maximum temperature was passed. The increased amounts of amino acid and amino sugar N accounted for 89% (urea treatment) and 68% (cyanamide treatment) of the added N remaining in compost.