The Effects of Biofertilizer Derived from Fermentation Effluent on the Structure and Function of Microbial Communities in Maize Soils, Northeastern China
To investigate the associations of a biofertiliser derived from fermentation effluent with microbial community composition and soil physicochemical properties in northern maize cropping systems, we conducted a field trial with three fertilisation treatments (macronutrients only, T1; macronutrients plus micronutrients, T2; and fermentation effluent combined with nutrients, T3) and one conventional control (CK) in continuously cropped maize soils. Soil physicochemical properties, microbial diversity and community composition, and predicted functional potential were analysed using high-throughput amplicon sequencing and standard soil assays. The results indicated that, compared with other treatments, the biofertiliser treatment (T3) was associated with significantly higher soil electrical conductivity, available phosphorus and alkali-hydrolysable nitrogen, but showed no significant effect on total organic carbon or organic matter. Bacterial community diversity did not differ significantly among treatments, whereas the fungal community appeared more sensitive to fertilisation. Principal coordinate analysis (PCoA) supported by PERMANOVA tests revealed that the treatments significantly altered fungal community structure. The phyla Acidobacteriota, Actinobacteriota and Firmicutes (including the genus Bacillus) were relatively enriched in the T3 treatment, while Ascomycota and Mortierellomycota were the dominant fungal phyla across all treatments. Redundancy analysis (RDA) indicated that available potassium, available phosphorus, and pH were key factors associated with microbial community structure. Functional gene inference, based on taxonomic annotation, suggested that the biofertiliser was correlated with predicted functional potential related to soil carbon and nitrogen cycling. In conclusion, the biofertiliser derived from fermentation effluent was correlated with improved soil nutrient availability and with putative shifts in microbial community composition in northern maize fields, thereby providing technical support for the resource utilisation of agricultural waste and the conservation of black soil.