Decomposition characteristics of different organic materials in coal mine reclamation area

Objectives The decomposition processes and nutrient release characteristics of different organic materials were studied for the reasonable use of organic resources in the reclamation of soil in mining areas.

Methods There reclamation soil was located in loess hilly mining area, Shanxi Province. Four kinds of organic materials were used in a decomposing experiment, they were wheat straw (WS), maize straw (MS), cow manure (CM) and pig manure (PM). All the tested materials were air-dried and cut into 2 mm pieces. Each material (containing 8 g of organic carbon) was loaded into a nylon net bag, then buried 15 cm deep into the soil, and 36 bags were prepared for each material. The sample bags were collected on the 12, 23, 55, 218, 280 and 365 days since buried, the dry matter residue and nutrient contents were measured.

Results All the tested straws and manures decomposed rapidly in the first 12 days and then dropped rapidly. After 365 days’ decomposition, the dry matter residual rates of WS, MS, CM and PM were 49.8%, 55.1%, 79.2% and 54.0%, organic carbon residual rates were 48.8%, 53.4%, 63.9% and 51.8%. The release of nutrients from straws and manures were varied. The N and P were enriched in the first 23 days, the residual rates of N and P in 23 days reached 131.0% and 152.7% in MS. The N residual rates of WS, CM and PM were 93.0%, 81.3% and 67.8%, and the P residual rates were 92.5%, 98.8% and 84.3%, respectively. After 365 days, the nutrient release rate in WS was K > P > N, and in MS, CM and PM were K > N > P. During the whole decomposition period, the N and P in the MS were enriched first, and then diluted, while in WS, CM and PM were continuously diluted. The order of decomposition rate constants (K) were PM > WS > MS > CM. The decomposition rates increased with the increase of P and hemicellulose contents, while decreased with the increase of lignin content, C/N and lignin/N.

Conclusions The decomposition rates of straw and manure in reclaimed soil in Shanxi mining area reache the maximum on the 12th day and then slowed down. Compared with straw, manures have a higher organic carbon residual and a faster release of N and P. Cow manure has the lowest decomposition rate and the highest organic carbon residual rate, so it is preferred organic material for the fertilizing of reclaimed soil in mining areas.