Microbial induced carbonate precipitation improving carbon sequestration of coastal saline soil

High salinity and poor physical structure of coastal saline soil lead to the rapid oxidative decomposition of soil organic carbon (SOC) and greenhouse gas emissions. This study investigated effect of organic fertilizer application (Group OF) and it combining with microbial induced carbonate precipitation (MICP) (Group MICPOF) on the rapid formation of soil aggregates in coastal saline soil and its carbon sequestration performance. Results showed that MICPOF not only increased mean weight diameter (MWD) of soil aggregates by 79.43%, but also reduced content of exchanging Na (E-Na) by 15.36% comparing with control group (CK) after 90-days treatment, which were significantly higher than OF. Besides, content of mineral-associated organic carbon (MAOC) increased 24.95% in MICPOF comparing with CK, which contributes to SOC stability. Results of 3D-EEM and FT-ICR-MS showed that MICPOF treatment improved humification of dissolved organic matter (DOM) and mineral-associated organic matter (MAOM), and increased the relative abundance of biorefractory substances such as lignin, tannins and aromatic compounds. Moreover, at the end of treatment, the cumulative CO2 emission in MICPOF decreased by 25.70% and 43.85% respectively comparing with CK and OF. Metagenomic analysis showed that MICP treatment increased the relative abundance of chemoautotrophic microorganisms such as Muriiphilus and Sulfurivermis. Besides, abundance of functional genes involved in calvin cycle, an important chemoautotrophic carbon sequestration pathway, in MICPOF was 39.37% and 29.11% higher than CK and OF, respectively. These results indicate that MICP has great potential to improve coastal saline soil and enhance its carbon sequestration.