Decomposition and chemical composition of cereal straw

The influence of environment, management practices and cultivar on the rate of cereal straw decomposition was assessed in laboratory and field studies. Decomposition was measured using the reduction in dry wt as an indicator of decomposition. The rate of straw decomposition decreased with reductions in water potential at potentials below − 0.1 MPa. The decomposition rate at−0.01 MPa was lower than at −0.1 MPa. The rate of straw decomposition increased with increasing temperature over the range measured (5–35°C). Buried straw decomposed more rapidly than surface straw in all treatments except at −0.01 and −5.0 MPa. The influence of three stubble management practices on the rate of decomposition of straw of two wheat cultivars, Suneca and Kite, was assessed in field experiments lasting 2 yr. The rate of decomposition was greatest following the partial incorporation and burial of wheat residues. The retention of residues on the soil surface retarded decomposition. The straw of wheat and barley cultivars tested in the laboratory varied significantly in respect of the rate of decomposition. The straw of barley cultivars decomposed more rapidly than straw of the wheat cultivars tested. In the field studies there was no significant difference in the rate of decomposition of straw of the two cultivars. The percentage of hot water-soluble components, hemicellulose and cellulose decreased, while the proportion of lignin increased as the straw decomposed. Total N increased in buried straw, but decreased in the straw retained on the soil surface. There was no relationship between the amount of a chemical component and the rate of straw decomposition other than the higher percentage of hot water-soluble components found initially in barley straw.