Influence of the Application of Non-Hazardous Sewage Sludge on the Evolution of Soil Carbon Pool and Carbon Pool Management Index

Abstract

The products of non-hazardous commercial sewage sludge were utilized in the accordance of the national standard in the experiment with sandy fluvo-aquic soil under wheat-maize rotation system during 2013 to 2015. The experiment focused on the effects of the use of non-hazardous sewage sludge on soil carbon pool and carbon pool management index to provide theoretical and technical basis for the resource utilization of non-hazardous sewage sludge. The results showed that compared with CK, soil amended sludge significantly improved soil total organic carbon (TOC), soil microbial biomass carbon (SMBC), labile organic carbon (LOC),and dissolved organic carbon (DOC) to 8.40-14.74 g·kg-1, 164.45-257.45 mg·kg-1, 3.58-4.88 g·kg-1and 81.16-101.58 mg·kg-1, soil amended sludge significantly enhanced SMBC, LOC and DOC by 84.00%-188.07%, 26.26%-58.03%, and 109.58%-185.39% (P<0.05) respectively, and 45 t·hm-2 sewage sludge (W3) had the most significant impact on soil carbon pool. The soil microbial entropy (SMBC/TOC), and utilization of labile organic carbon (LOC/TOC) increased by 8.02%-2.77% and 13.75%-46.48% respectively, and the utilization of dissolved organic carbon (DOC/TOC) significantly decreased by 153.45%-195.40% (P<0.05). SMBC/TOC, LOC/TOC, and DOC/TOC declined in treatments of soil amended sludge due to increased application of sewage sludge, which indicated that soil amended with 45 t·hm-2 of the sewage sludge improved the content of stable carbon resulting in the decease of the ratio. L and LI decreased with the increasing amount of sewage sludge indicating that soil amended with 45 t·hm-2 of the sewage sludge improved the content of stable carbon and was conducive to the accumulation of organic carbon. Soil amended with sludge significantly increased carbon pool management index (CMPI) by 153.45%-195.40% (P<0.05), and W3 had the most significant effect on CMPI. Compared with TOC, CMPI could be more sensitive and direct to reflect the dynamic changes of soil nutrients and carbon pools through the correlation analysis and redundancy analysis. In summary, the application of 15-45 t·hm-2 sewage sludge could significantly enhance the soil carbon pool and carbon pool management index, especially 45 t·hm-2 sewage sludge (W3).