Conservation tillage regulates soil bacterial community assemblies, network structures and ecological functions in black soils

Abstract

Aims Conventional tillage is a serious threat to the stability of soil ecosystems. Understanding the response mechanisms of soil microbial community assemblies to anthropogenic activities is a major topic of ecological research. Methods Here, we investigated the bacterial community structures and assemblies in bulk and rhizosphere soils of soybeans grown with conventional tillage (moldboard plow, MP) and with conservation tillage that involved no-tillage (NT) or ridge tillage (RT) using high-throughput sequencing methods. Results We found that soil bacterial community compositions, structures and assembly processes were primarily altered by tillage practices. Briefly, in comparison to MP, NT and RT increased the relative abundances of the nitrogen-fixing bacteria Mesorhizobium sp., Bradyrhizobium sp. and Burkholderia sp., but decreased the abundance of soil carbon-degrading bacteria, especially Blastococcus sp., Streptomyces sp. and Sphingomonas sp. In addition, in comparison to MP, NT and RT resulted in more stable bacterial networks and more lower the relative contribution of homogenizing dispersal. Soil pH was the primary soil factor regulating both the bacterial community structures and assembly processes under the three tillage practices. Conclusions The altered functional bacteria under conservation tillage was mostly affiliated with biomarkers and keystone taxa, inferring that conservation tillage might contribute to biological nitrogen fixation and soil carbon sequestration.