Response of organic carbon fractions and microbial community composition of soil aggregates to long-term fertilizations in an intensive greenhouse system

Purpose Soil organic carbon (SOC) content and stability, which are regulated by microbial communities, vary depending on aggregate size. The objectives of this study were to investigate the distribution of the SOC fraction and microbial community composition within soil aggregates when subjected to different fertilization treatments. Materials and methods This study used high-throughput sequencing technology to analyze the soil microbial community distribution in different-sized aggregate fractions [> 2 mm (large macro-aggregates), 2-0.25 mm (small macro-aggregates), and < 0.25 mm (microaggregates)] when they were subjected to different fertilization treatments in a 16-year greenhouse experiment. The three treatments were chemical fertilizer (CF), 50% organic fertilizer + 50% chemical fertilizer (MF), and organic fertilizer (OF). Results and discussion The results showed that the application of organic fertilizer significantly increased the soil organic carbon (SOC), dissolvable organic carbon (DOC), and microbial biomass carbon (MBC) contents and changed microbial community composition in all the different-sized soil aggregates. We observed that OF significantly reduced the relative abundance of bacterial communities in all aggregates and significantly increased the relative abundances of fungal communities in small macro-aggregates. The larger fungal communities in small macro-aggregates could promote soil aggregation and C sequestration. Conclusions Organic fertilization increased the substrate contents in soil aggregates and enhanced soil aggregation and microbial activity in macro-aggregates, which are critical factors that facilitate C transformation and sequestration. These improvements resulted in significantly improved soil fertility and increased vegetable yield in the greenhouses.