Effects of microbial inoculants on the physicochemical properties and fungal communities of kiwifruit rhizosphere soil

Kiwifruit cultivation has long been challenged by issues such as improper fertilization, continuous cropping obstacles, and unsuitable soil pH, leading to soil nutrient imbalance, disruption of microbial community structure, and frequent soil-borne diseases, which affect the yield and quality of kiwifruit. The application of microbial inoculants is considered an important strategy to address these problems. In this study, a pot experiment was conducted with four treatments: blank control (T1), application of Bacillus sp. (T2), combined application of Bacillus sp. and nitrogen-fixing bacteria (T3), and combined application of Bacillus sp., nitrogen-fixing bacteria and Burkholderia sp. (T4), to explore the effects of different microbial inoculants on the physicochemical properties and fungal communities of kiwifruit rhizosphere soil. The results showed that, compared with the control group (T1), the T3 treatment had the most significant effect on improving soil physiocochemical properties. The T3 treatment significantly increased the levels of total potassium, total nitrogen, total carbon, organic matter, and organic carbon in the rhizosphere soil while reducing soil pH. Moreover, the T3 treatment significantly enhanced the activities of soil enzymes, including peroxidase, protease, phosphatase and urease. Principal coordinate analysis (PCoA) indicated that the appliaction of microbial inoculants significantly influenced the diversity of fungal communities in the rhizosphere soil. Fungal community structure analysis revealed that Ascomycota and Basidiomycota were the dominant fungal phyla, while Plectosphaerella, Mortierella and Chaetomium were the dominant genera. Compared with the control group, the relative abundance of Ascomycota increased significantly in all treatments, whereas the relative abundance of Mortierella decreased significantly. Correlation analysis further demonstrated that the influence of kiwifruit rhizosphere soil physicochemical properties and fungal community structure was the result of their interactions. In conclusion, the combined application of Bacillus sp. and nitrogen-fixing bacteria is an effective strategy for improving the physicochemical properties of kiwifruit rhizosphere soil and optimizing fungal community structure. This study provids scientific evidence to for the sustainable use of soil in kiwifruit cultivation areas.