Changes in soil microbial activity and ecological function can be used to assess the level of soil fertility and the stability of ecosystems. To assess the fertility and safety of organic fertilizer of kitchen waste (OFK), soils containing 0% (CK), 1%, 3%, and 5% OFK were cultured, and the physical, chemical, and microbial properties of the soils were measured dynamically with routine agrochemical analysis measures and amplicon sequencing. The results showed that compared with those in CK, the contents of organic matter, available phosphorus, available potassium, NH4+-N, and NO3--N in soils with OFK increased by 23.80%-35.13%, 13.29%-29.72%, 16.91%-39.37%, 164.7%-340.2%, and 28.56%-32.71%, respectively. The activities of hydrolases related to the cycle of carbon, nitrogen, and phosphorus (α-glucosidase, leucine aminopeptidase, acid phosphatase, etc.) were also significantly higher than those of the CK treatment. OFK stimulated the growth of soil microorganisms and increased the carbon content of the microbial biomass. The amplicon sequencing analysis found that the microbial community structures of different treatments were significantly different at both the class and genus levels. In addition, it was found that the abundance of beneficial microbes in the soils with OFK increased, whereas pathogenic microbes decreased. RDA results confirmed that soil properties (including soil pH, organic matter, available nutrients, and microbial biomass) had a significant impact on microbial community structure. The results of investing bacterial community based on PICRUSt and FAPROTAX revealed that the function of the soil bacterial community was similar in the four treatments, but OFK supply significantly improved the microbial carbon utilization and metabolic ability. Moreover, by using the FUNGuild software, we found that the application of OFK increased the proportion of saprotroph-symbiotroph and symbiotroph and stimulated the growth of ectomycorrhizal fungi-undefined saprophytic fungi but inhibited plant and animal pathogenic fungi in soil. These results implied that OFK could promote the establishment of symbiotic relationships and inhibit the growth of pathogenic fungi. In summary, OFK could improve soil fertility and hydrolase activity, stimulate the growth of beneficial microorganisms, and defend against pathogens, indicating a promising use as safe and efficient organic fertilizer.
Keywords: enzyme activity; microbial community composition; microbial community function; nutrients; organic fertilizer of kitchen waste （OFK）.