Effects of Earthworms and Phosphate-Solubilizing Bacteria on Carbon Sequestration in Soils Amended with Manure and Slurry: A 4-Year Field Study

Abstract

The application of organisms as part of soil remediation can accelerate the decomposition of organic matter and the carbon cycle. To explore the synergistic effects of earthworms and phosphate-solubilizing bacteria on C accumulation in artificially improved soils of manure and in slurry-amended soil, a dry slope of land was established on the hillside of a large pig farm. Experiments involving six treatments were performed, including control (CK), pig manure (Pm), and pig manure + slurry (Pm + S) treatments, as well as manure + slurry + earthworms (Te), manure + slurry + phosphate-solubilizing bacteria (Tb), and manure + slurry + earthworms + bacteria (T(e + b)). Compared with the CK, both the Pm + S and T(e + b) treatments significantly increased the SOC content. In particular, the T(e + b) treatment increased the SOC by 196%. The synergistic effect of T(e + b) on the increase in organic carbon was consistent with the results of soil-carbon sequestration. After comprehensive fertilization, soil-carbon sequestration reached 2.87 Mg C hm−2, while stable organic carbon increased to 1.88 Mg C hm−2. It was also consistent with the result of PCA analysis in which applying earthworms promoted an increase in insoluble organic carbon. Therefore, in the future, earthworms and organic fertilizers can be applied to promote organic carbon sequestration on dry sloping land.