Mulching practices manipulate the microbial community diversity and network of root‑associated compartments in the Loess Plateau

The Loess Plateau of China is a typical dryland farming region. It is known that mulching practices can maintain soil hydrothermal environment and improve crop production. However, it is not clear how mulching affects root-associated microbiomes in the successive growth stages of broomcorn millet (Panicum miliaceum L.). Here, we investigated the effects of traditional flat planting (TP), plastic film mulching (PFM), and ridge-furrow rainwater planting (RF) on the bacterial and fungal diversity, composition, co-occurrence networks, and assembly in bulk soil, rhizosphere, and root compartments at the jointing and flowering stages of broomcorn millet. Bacterial and fungal community composition and structure in all three compartments were more affected by the PFM and RF treatments than by the TP treatment. Mulching measures did not affect the bulk soil bacterial and fungal diversity, but reduced the bacterial diversity and increased the fungal diversity of rhizosphere and root system at flowering stage of broomcorn millet. Indicator taxa analysis showed more shared and specific species in rhizosphere bacterial and fungal networks. Mulching induced specific responses from taxa/modules of bacterial and fungal co-occurrence networks in the three compartments. In the bulk soil and rhizosphere meta-networks, Actinobacteria and Firmicutes were the keystone taxa, and the relative abundance of Actinobacteria in root meta-networks decreased in the PFM and RF treatments compared to that in the TP treatment. We also noted that mulching affected the bacterial assembly process in three compartments, but did not affect the fungal assembly process. Overall, our findings provide basic insights into the broomcorn millet root-associated ecosystem and sustainable development of drylands.