Long-term soil management practices influence the rhizosphere microbial community structure and bacterial function of hilly apple orchard soil

Long-term traditional clean tillage (CT) causes soil nutrient losses in hilly apple orchards. Thus, suitable soil management practices are needed to reduce these losses and achieve high yields and sustainable apple production. Different soil mulching practices have been gradually adopted in modern apple orchards, such as black plastic film mulching (BPFM), sawdust mulching (SDM), biochar mulching (BCM), maize straw mulching (MSM), and wild-growing grass mulching (WGGM). Soil microbial communities are considered to be key ecological indicators of soil conditions. Therefore, using Illumina MiSeq, this study evaluated the influence of different soil management practices on the soil microbial community in an apple orchard in western Liaoning, China. The results showed that, compared with the CT, SDM, MSM and WGGM increased the abundance of fungal operational taxonomic units, exerted positive effects on the alpha diversity of fungi, and improved the stability of the soil ecosystem, these effects were even stronger in the SDM, whereas BCM increased the abundance of bacterial operational taxonomic units, but reduced the fungal alpha diversity, and was unfavourable for growth of fungi and maintenance of soil stability, while BPFM reduced the bacterial alpha diversity, and was not be conducive to the colonisation of bacteria. Compared with the CT, the other five soil management practices all affected the bacterial PICRUSt function related to nutrient absorption and utilisation, and more drastic changes were observed in the SDM. The pH, total phosphorus, total carbon and the ratio of C:N were important environmental factors that affected the relative abundance of dominant bacterial and fungal taxa. Overall, our results indicated that the application of mulching practices, especially sawdust mulching in the hilly apple orchard enhanced the richness and diversity of the microbial community, altered the community composition and bacterial ecosystem function, and improved the soil ecosystem stability. This study provides a theoretical reference for the selection of soil management practices for hilly apple orchards.