Decomposition process and residual rate of organic materials C and N in soils

By using nylon mesh bags and sand filter tubes, this paper studied the decomposition of organic materials in the soils at Shenyang and Hailun eco-experimental stations of CAS to investigate the dynamic changes of their organic C and N during decomposition. The results showed that the decomposition process could be divided into two phases, i.e., quick phase and slow phase. The organic N in the materials had an obviously lower decomposition rate than organic C, and thus, had a higher residual rate. The decline of C/N ratio could be also divided into quick and slow phases. After 3-5 years decomposition, the C/N ratio of all test materials tended to be stable. The C/N ratio of the residual organic materials with an initial lower C/N (such as pig manure) approached to that of soil humus, being about 10, which indicated that the humification process was completed, while that of the residual organic materials with an initial higher C/N was about 25, being available to the activities of soil microbes, which would benefit the increase of soil organic matter and the improvement of soil fertility.