Soil microbial communities in cucumber monoculture and rotation systems and their feedback effects on cucumber seedling growth

Abstract

Loss of biodiversity caused by intensive agriculture is a major worldwide concern. Crop rotation can enhance crop productivity and increase soil microbial diversity. However, the functional significances of changes in soil microbial communities are poorly understood. Soil microbial communities from a cucumber monoculture system and the cucumber season of a two-year rotation system (tomato-celery-cucumber-Chinese cabbage) were analyzed by quantitative PCR and high throughput amplicon sequencing. Then, feedback effects of soil biota on cucumber seedlings were evaluated through soil sterilization, addition of soil inoculum, and application of bactericide and fungicide. Crop rotation increased cucumber yield and bacterial diversity, but decreased fungal diversity and abundance. The bacterial and fungal community compositions also differed between the two cropping systems. Abundances of potential plant pathogens and antagonistic microorganisms were lower while potential plant-growth-promoting microorganisms were higher in the rotation system. The overall effect of soil biota was positive on cucumber seedling growth, and was stronger in the rotation system. Increasing temporal plant diversity can change soil microbial communities and enhance crop productivity through positive plant-soil feedbacks mediated by soil biota.