Effect of long-term fertilization on bacterial community in a sandy loam soil and its relation to organic carbon accumulation

¹ Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes, Ministry of Education, College of Environment, Hohai University, Nanjing 210098, China
² State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China

^* Corresponding author: envly@hhu.edu.cn

Abstract

Fertilization can affect the transformation of soil organic carbon (SOC) and soil microbial community composition. However, thus far, how SOC accumulation in association with bacterial community is still unclear. We collected arable soils (aquic inceptisol) from a long-term fertilization experiment (20 years) including compost (CM), inorganic nitrogen + phosphorus + potassium (NPK), half compost N plus half inorganic fertilizer N (HCM), NP, NK, PK, and untreated (Control). We investigated the relationship between the SOC accumulation rate and bacterial community composition measured by high-throughput sequencing. The highest SOC accumulation rate was observed in the compost treatments. Furthermore, compost and balanced NPK treatments increased soil carbohydrate content significantly (P < 0.05), while no such enhancement was observed following NK and PK application. Compared with the Control, fertilization substantially reduced the effective diffusion coefficient of oxygen in soil. Meanwhile, fertilization lowered the relative abundance (RA) of Bacteroidetes but increased the RA of Proteobacteria. Compost application increased the RA of Firmicutes, while inorganic fertilizers reduced it. The RA of Proteobacteria and Firmicutes were significantly and positively correlated with the SOC and carbohydrate content and the SOC accumulation rate (P < 0.05). SOC accumulation was also accompanied with the reduction in the effective diffusion coefficient of oxygen in soil. Our results indicated that poor aeration may induce a shift in the microbial community composition and a transition from aerobic to anaerobic degradation of SOC, thereby favoring SOC accumulation.