Soil Organic Carbon of Purple Soil as Affected by Different Application of Biochar

Abstract

Soil organic carbon (SOC) is the most important part of the soil carbon pool and soil labile organic carbon is a key indicator of changes in the soil carbon pool. In order to study changes in SOC and its labile components with different biochar additions to soil, a field experiment was conducted at Chongqing National Purple Soil Fertility and Fertilizer Efficiency of Long-Term Monitoring Station. Different amounts of biochar (0 kg·hm-2, CK; 4000 kg·hm-2, 0.5 BC; 8000 kg·hm-2, BC; 16000 kg·hm-2, 2BC) combined with fertilizer were applied to purple soil in this hilly area. SOC and soil labile carbon content were determined for purple soil rape-maize rotation systems. Results showed that:① Application of biochar can significantly improve SOC content; within a certain range, the amount of added biochar is correlated with SOC content. The content of soil microbial biomass carbon (SMBC) increased with application of 8000 kg·hm-2 biochar, but decreased with application of 4000 and 16000 kg·hm-2. The content of dissolved organic carbon (DOC) and readily oxidized carbon (ROC) in soil increased with different amounts of biochar; the highest DOC (198.83 g·kg-1) and ROC (4.86 g·kg-1) were obtained under low biochar addition treatments. ② The application of biochar significantly decreases the ratio of soil ROC to SOC and microbial entropy. The ratio of soil ROC to SOC and microbial entropy of 0.5 BC treatment are 20.45% and 4.11%, respectively, lower than for CK. Moreover, 0.5 BC and BC treatments can significantly improve the ratio of soil DOC to SOC. In summary, biochar addition in soil leads to low soil microbial activity but higher soil stability. An appropriate biochar treatment can stimulate accumulation of SOC, and 0.5BC treatment can improve soil DOC and ROC.