Changes in soil microbial community and co-occurrence network after long-term no-tillage and mulching in dryland farming

Background Conservation tillage practices (e.g., no-tillage and mulching) have been promoted as effective strategies for agro-ecosystems, but the mechanisms related to agricultural production in arid regions are unclear from a microbial perspective. Methods We investigate the effects of different tillage systems (conventional tillage (CT) and no-tillage (NT)), and mulching patterns (straw mulching (SM), plastic film mulching (PM), and no-mulching (NM)) on the soil bacterial and fungal communities, co-occurrence networks, their relationships with soil properties, based on a field experiment conducted for 17 years. Results The interactions between tillage and mulching significantly affected the soil physicochemical properties and maize yield, and the effects of mulching were greater than those of tillage. Compared with NM, PM and SM increased the grain yield by 26.0% and 15.6%, respectively. The soil bacterial community α-diversity was mainly affected by tillage, primarily because NT increased the soil water content (SWC) and reduced the destruction of microhabitats, thereby increasing the soil bacterial Chao1(by 4.3%) and Sobs (by 3.4%) indices compared with CT. The effect of mulching treatments on soil microbial community structure was greater than that of tillage treatments, confirmed by the distribution of treatment-sensitive OTUs (tsOTUs). The abundance of tsOTUs (e.g., Sphingomonadales and Sordariales ) increased with PM due to higher soil temperature (Tem), leading to enhanced conversion of total nutrients into available nutrients and ultimately increasing grain yield. The SM positively affected the microbial (e.g., Burkholderiales and Sordariomycetes ), mainly by increasing the SWC and total nitrogen content. However, low Tem (0.87 of the total effects) inhibited the positive effect of organic matter addition on grain yield under SM. Moreover, SM increased the stability of the co-occurrence network, which is reflected in keystone taxa, average clustering coefficient, and modularity. Mulching also increased the importance of stochasticity processes in soil bacterial communities, and the soil environmental variables (SOC, pH, etc.) were critical to the construction of communities. Conclusion Compared with SM, PM increases yield more, but input could also be increased because of depleting soil nutrients. At a low input level, SM increased the diversity and stability of the soil microbial community and maize yield. Overall, our findings indicate that SM is a promising approach for dryland farming systems.