Short-term effects of mechanical drainage on fungal and bacterial community structure in a managed grassland soil

- We survey changes in soil microbial communities caused by mechanical drainage.
- Mechanical drainage does cause significant changes to abundances of certain phyla.
- Overall soil microbial community structure and diversity remained unchanged.

This study focused on identifying the short-term effects of mechanical drainage on the structure and diversity of fungal and bacterial communities in soil. Mechanical drainage is a widely used agricultural practice which allows for the management of surface and sub-surface water. It is vital for improving land productivity and reclaiming marginal land. The use of mechanical drainage is known to have several impacts on the physico-chemical components of soil; however, little is known about its effect on the soil microbiome. In the present study, 454 pyrosequencing of the 18S and 16S rRNA gene regions was used to evaluate differences in fungal and bacterial communities in soil samples taken pre and two months post drainage from an extensively managed grassland in Co., Meath, Ireland.Mechanical drainage was found to have no significant impact on soil pH or on soil carbon and nitrogen levels, however a statistically significant reduction in moisture content was recorded (c. 7%). Analysis of metagenetic data showed that Basidiomycota was the largest classifiable fungal phylum accounting for 16% of all sequences. The predominant bacterial phyla identified in all samples were Proteobacteria, Bacteroidetes and Acidobacteria with average relative abundances of 23%, 26% and 27% respectively. Overall fungal and bacterial community structure and diversity remained unchanged in response to mechanical drainage but two fungal phyla, Chytridiomycota and Blastocladiomycota, showed a significant increase in relative abundance in response to drainage. These findings contribute to our overall understanding of how mechanical drainage impacts the soil microbiome.