Reduced Chemical Fertilizer Combined with Organic Fertilizer Alters the Soil Microbial Community and Enhances Soil Microbial Diversity of Acanthopanax senticosus Cultivation

To investigate the response of soil microbial communities to reduce chemical fertilization supplementation with organic fertilizer in <i>Acanthopanax senticosus</i> cultivation, we analyzed the diversity, composition, and structure of soil microbiota by using high-throughput sequencing technology. The results showed that reducing chemical fertilizer application significantly increased soil microbial richness (ACE and Chao1 indices), which was positively correlated with soil total nitrogen (TN) content. At the phylum level, the relative abundance of Cyanobacteria decreased at T2 (reduction of 20% for fertilizer application) but increased at T4 (reduction of 60% for fertilization application), exhibiting an opposite trend to Bacteroidetes. At the genus level, the relative abundance of Paucibacter was significantly higher in T4 than in other treatments, while Nitrospira reached its peak under T3 treatment. For fungal communities, the richness index showed a non-linear response, initially decreasing and then increasing, which was positively correlated with the soil available potassium (AK) content. At the phylum level, reduced fertilizer application significantly reduced the relative abundance of Ascomycota compared to conventional fertilization. At the genus level, the relative abundance of Fusarium was significantly lower in the T4 treatment than in the other treatments. Redundancy analysis (RDA) revealed that the total organic carbon (TOC), TN, and AK were the key environmental factors affecting the soil microbial community. This study demonstrated that partial substitution of chemical fertilizers with organic amendments can improve soil physicochemical properties and enhance microbial diversity, providing a scientific basis for developing sustainable fertilization strategies for <i>Acanthopanax senticosus</i> cultivation.