|HORWATH W R|
|ELLIOTT L F|
Submitted to: Plant and Soil
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/23/1995
Publication Date: N/A
Interpretive Summary: Composting of high C:N ratio materials such as crop residues normally requires co-composting with low C:N ratio materials to lower C:N ratios to 30:1 or less. Grass seed production residues are being composted successfully in the field using a low-input, on-farm approach without co-composting. It appears that conditions are being established for optimum lignin degradation. These results will be used to extend the application of these principles to other crop residues.
Technical Abstract: The biochemistry of perennial rye grass straw decomposition was examined under mesophilic and thermophilic conditions. The change in straw lipids, sugars, soluble polysaccharides, cell wall polysaccharide, lignin, and element composition was determined during 45 days of laboratory incubation. Thermophilic conditions were used to examine processes occurring during composting of rye grass straw residue. The straw chemical fractions and C, H, and O content declined steadily under both temperature regimes. No change in N content was observed. Acid insoluble lignin content declined 10 percent at mesophilic and 29 percent at thermophilic conditions. Carbon analysis of the acid unsoluble lignin revealed that lignin C loss was 25 percent at mesophilic and 39 percent at thermophilic conditions. It was calculated that 94 percent of the lignin was altered based on the change in C, N, H, and O content. The oxidation of lignin and accumulation of humic substances is postulated as a reason for the change and alteration of the lignin fraction during rye grass straw decomposition. The extensive lignin decomposition provides evidence why high C-to-N ratio rye grass straw composts successfully without co-composting.