Responses of rhizosphere bacterial communities with different niche breadths to liquid fertilizer produced from <i>Fuji</i> apple wastes during planting process

The application of fertilizer in agroecosystems exerts a significant influence on the regulation of soil microbial community and soil properties. However, the impact of liquid fertilizer derived from apple wastes on soil properties, microbiota, and plant growth remains unclear. In this study, we investigated the effects of apple waste liquid fertilizer on rhizosphere microbiota and soil characteristics by analyzing both the bacterial community and physicochemical properties of the soil. The results demonstrated that the application of liquid fertilizer significantly influenced the diversity and structure of bacterial communities. Furthermore, the application mainly increased the niche breadth of bacterial communities, while exerting minimal impact on the assembly process. The rhizosphere bacterial communities treated with a high concentration of liquid fertilizer exhibited increased diversity and broader niche during the late planting period. Moreover, bacterial cooccurrence networks revealed that communities following the application of liquid fertilizer exhibited reduced network nodes and edges, as well as smaller network sizes. These communities were characterized by increased modularity and interconnectedness facilitated by key bacterial indicators such as <i>Sphingomonas</i>. The presence of indicators representing different niche breadths in bacteria showed significant correlations with available nitrogen (AN) and available phosphorus (AP), while positively correlating with the Bray-Curtis dissimilarity. Following the application of high concentration liquid fertilizer, the number and relative abundance of specialist ASVs such as <i>Sphingomonas</i>, Gp6, and <i>Arthrobacter</i> increased. The results suggested that liquid fertilizer impacted the soil AN and AP through alterations in the recruitment pattern of specialist ASVs. Also, liquid fertilizer treatment significantly increased the abundance of carbohydrate metabolism and biosynthesis of other secondary metabolites pathway genes of bacterial communities. Plant height, leaf length, leaf width, and dry weight of plants were significantly increased in plants treated with liquid fertilizer These results suggested that the application of liquid fertilizer could result in variations in the microbial community composition, structure, and function. The composition of the liquid fertilizer and the potential functional microorganisms still need to be further studied.IMPORTANCEThe issue of arable soil degradation is of global importance, and the utilization of agricultural waste plays a pivotal role in enhancing soil properties and promoting sustainable crop production. In particular, elucidating how agricultural waste affects the microbial composition and regulates soil properties is extremely relevant at both fundamental and practical levels. The bioinformatics analysis of microbiota from field experiments revealed that the application of liquid fertilizer from apple wastes significantly affected the structure and co-occurrence network of rhizosphere bacterial communities. Also, it was observed that the planting time also influenced the community structure. Additionally, the soil available nitrogen (AN) and available phosphorus (AP) were significantly influenced by bacterial communities, leading to alterations in soil properties. Finally, liquid fertilizer treatment significantly affected the function of soil bacteria community and promoted the growth of bok choy.