Decomposition dynamics and driving factors of manure in reclaimed soils in coal mining area

Abstract

Understanding the decomposition dynamics and driving factors of manure in the soil subjected to different reclaimed years could provide theoretical basis to rational utilization of manure and soil fertility improvement in coal mining area. Cattle manure and pig manure were mixed with soils subjected to different reclaimed years (one year, R1; 10 years, R10; and 30 years, R30) at the ratio of manure carbon to soil mass of 4 to 100, so as to examine manure decomposition characteristics using the nylon mesh bag (15 cm deep of soil buried) in the Shanxi coal mine reclamation area, with no manure addition as control (CK). Soil samples were collected at day 12, 23, 55, 218, 281, and 365 to measure the contents of soil manure residual, soil microbial biomass carbon (MBC), and dissolved organic carbon (DOC). The contributions of soil properties, manure properties, and hydrothermal condition to manure decomposition were quantified. The results showed that the decomposition rates of pig manure were significantly higher than cattle manure. The humification coefficient of pig manure (average 46.3%) was lower than that of cattle manure (average 71.7%). The humification coefficient of pig manure was significantly lower in the 30-year reclaimed soil (44.5%) compared to the 1-year and 10-year reclaimed soil (average 47.2%). There was no significant difference in the humification coefficient of cattle manure among the three reclaimed soils. The proportion and decomposition rate constant of labile carbon pool of pig manure and cattle manure were significantly different, with values of 52% and 26%, and 0.00085 and 0.00074 ℃-1, respectively. The positive effect of pig manure on MBC and DOC in reclaimed soil was significantly higher than that of cattle manure over 0-218 days, but no difference over 281-365 days. The magnitude of the enhancement of MBC and DOC in those three reclaimed soils after manure amendments showed a similar trend of R1 >R10 ≈ R30. Results of variance partitioning analysis showed that manure decomposition was mainly controlled by manure properties (17.9%) when considering soil properties, manure properties, and hydrothermal condition. In conclusion, the decomposition of pig manure but not cattle manure was regulated by reclamation year. Cattle manure, with higher humification coefficient than pig manure, was recommended for reclaimed mining area to improve soil fertility.