Effect of Biochar and Earthworm on Organic Matter Mineralization in Topsoil and Deep Soil

In recent years, biochar has been widely used for soil remediation because of its good soil amendment efficacy, but the effect of biochar addition on mineralization of soil organic matter (SOM) is still controversial. Earthworms, as common soil macrofauna, may change the effect of biochar on soil carbon stabilization. Therefore, 0.5% (w/w) corn biochar was added to top and deep soils respectively in the presence or absence of earthworms for 43 days of incubation experiment. The CO 2 release rates were monitored on the 2nd, 8th, 15th, 22th, 29th, 36th, and 43th days, differences in soil respiration rates and cumulative emissions were compared between biochar, earthworm and mixed culture groups, and changes in SOM composition were measured by DOC and 3D fluorescence before and after the culture groups. The results showed that the addition of biochar reduced the SOM mineralization, and the presence of earthworms significantly increase the soil respiration rate and soil carbon emission. Compared to deep soil, earthworms had a stronger respiration effect on top soil. In the short term, the addition of biochar stimulated the mineralization, especially in the topsoil, from earthworms. However, in the long time, the addition of biochar was beneficial to the reduction of the mineralization of SOM.