Response of soil microbial communities to continuously mono-cropped cucumber under greenhouse conditions in a calcareous soil of north China

Abstract

Microbes are the engines for nutrient cycling in the soil, playing an important role in maintaining soil quality and agricultural production, but it is unclear how soil microbial communities respond to continuously mono-cropped cucumber under greenhouse conditions. High-throughput sequencing of the bacterial 16S rRNA and fungal 18S rRNA gene fragments was conducted to compare the variations of microbial communities within greenhouse mono-cropped cucumber systems across 8, 15, and 22 cultivation years with new-build greenhouse of cucumber cultivated just for one season (1 year). Results showed that soil pH and fungal diversity significantly decreased, whereas soil EC, organic matter (OM), and nutrient concentrations (total nitrogen (N), nitrate N (NO3−-N), total and available phosphorus, and potassium) significantly increased when cucumber was mono-cropped for 8 or more years. The mono-cropped cucumber for 8 or more years reduced the relative abundance of the dominant bacterial phyla Actinobacteria, but increased the abundances of Acidobacteria and Firmicutes significantly compared with the cucumber planted for one season. Moreover, the predominant fungal phylum Ascomycota increased significantly with increasing cultivation years of cucumber. Soil OM and NO3−-N are most important factors to drive the variation of soil bacterial community, while soil pH, OM, and NO3−-N markedly responded to the changes of the fungal community in the greenhouse cucumber mono-cropped system. This research provides insights into the response of microbial communities to continuous mono-cropping cucumber, and this has implications on the sustainability of such intensive production systems.