Cropping practices manipulate soil bacterial structure and functions on the Qinghai-Tibet Plateau

There is an increasing awareness of the adverse environmental effects of the intensive practices used in modern crop farming, such as those that cause greenhouse gas emissions and nutrient leaching. Harnessing beneficial microbes by changing planting practices presents a promising strategy for optimizing plant growth and agricultural sustainability. However, the characteristics of soil microorganisms under different planting patterns remain uncertain. We conducted a study of soil bacterial structure and function under monoculture vs. polyculture planting regimes using 16S rRNA gene sequencing on the Qinghai-Tibet Plateau. We observed substantial variations in bacterial richness, diversity, and relative abundances of taxa between gramineous and leguminous monocultures, as well as between gramineae-legume polycultures. The number of operational taxonomic units and alpha and beta diversity were markedly higher in the leguminous monocultures than in the gramineous monocultures; conversely, network analysis revealed that the interactions among the bacterial genera in the gramineous monocultures were more complex than those in the other two planting regimes. Moreover, nitrogen fixation, soil detoxification, and productivity were increased under the gramineous monocultures; more importantly, low soil-borne diseases (e.g., animals parasitic or symbiont) also facilitated strongly suppressive effects toward soil-borne pathogens. Nevertheless, the gramineae-legume polycultures were prone to nitrate seepage contamination, and leguminous monocultures exhibited strong denitrification effects. These results revealed that the gramineous monoculture is a more promising cropping pattern on the Qinghai-Tibetan Plateau. Understanding the bacterial distribution patterns and interactions of crop-sensitive microbes presents a basis for developing microbial management strategies for smart farming.