[Impacts of Biochar Input on Mineralization of Native Soil Organic Carbon]

Since the biochar was applied in soil, its function in carbon sink had become a research hotspot recently. However, the present studies showed that its function in carbon sink remained controversial and the interaction between biochar and soil organic carbon remained to be investigated. So our study used paddy soil (C3 soil) as the experimental soil, and added washed (CS) or unwashed (CN) corn stalk (C4 crop). Biochar was mixed with soil uniformity by two kinds of weight, each treatment was 1% and 3% of the soil (CS1%, CS3% and CN1%, CN3%). Soil without biochar was used as the control treatment (CK), every treatments repeated three times. Then indoor culturing experiments was carried out to study the effect of biochar on the mineralization of organic carbon. The results showed as follows: (1) During the 180 days' experiment, the accumulated amount of released CO2 in CS1%, CS3% and CN1% groups were 1865.7, 1864.4 and 1856.2 mL x kg(-1) respectively, all were higher than the CK (1779.0 mL x kg(-1)). But the differences were not significant. However, the accumulated amount of released CO2 in the CN3% group was the highest (2289.1 mL x kg(-1)), which was significantly higher than those of all other groups. This showed that high addition of CS biochar significantly reduced the soil CO2 release. (2) The accumulated amount of released CO2 of native soil from the CK treatment, CS treatment and CN treatment were 1534.2, 1000.4 and 1153.7 mL x kg(-1) respectively, among which the CK group is significantly higher than the others. It showed that additions of two kinds of biochar both could inhibit the mineralization of organic carbon in the soil. The result of priming effect also proved that: the PE value of CS 3% group was -34.8%, and the PE value of CN 3% group was -24.8%. This showed that the negative priming effect significantly induced by washed (CS) biochar.