The changes in soil chemical properties and bacterial community structure after applying the compound microbial agent to Alpinia oblongifolia

To investigate the potential effects of a compound microbial agent on the soil bacterial community structure and nutrient content of Alpinia oblongifolia, the agent was applied to the rhizosphere via root irrigation. Rhizosphere and non-rhizosphere soil samples were collected before and three months after application to determine soil chemical properties and soil bacterial species abundance Results showed that the application of the compound microbial agent significantly increased both organic matter and total nitrogen content in both rhizosphere and non-rhizosphere soils (P < 0.05). Organic matter increased by 32.32% and 24.55%, respectively, while total nitrogen increased by 146.34% and 30.00%, respectively. At the phylum level, the dominant bacterial phyla in Alpinia oblongifolia soil were Acidobacteriota, Proteobacteria, Chloroflexi, Actinobacteriota, and Verrucomicrobiota. At the genus level, excluding unidentified genera, the dominant bacterial genera were Acidothermus, Bradyrhizobium, and Acidibacter. Correlation network analysis of the soil bacterial community showed that the correlation network structure of core genera in the soil bacterial community was relatively loose before the application of the inoculant. Three months after application, the number of core genera did not change, but the links between core genera became tighter, forming a network with Acidothermus, Bradyrhizobium, and Acidibacter as core genera. The application of the compound inoculant can effectively improve the soil, influence the composition of the Alpinia oblongifolia soil bacterial community, enhance the interaction among soil functional bacteria, and increase the nutrient content of Alpinia oblongifolia soil, thus potentially promoting the growth of Alpinia oblongifolia seedlings.