Consequences of elemental sulfur induced soil acidification on bacterial and fungal communities in Southern Okanagan vineyard soil

Elemental Sulphur (S°) can be used as a fertilizer, acidifier or biocide in agricultural ecosystems. S° changes soil pH and results in the production of metabolites toxic to many microbes. Bacteria and fungi have differential susceptibility to S° which may lead to changes in soil microbial communities and functioning. Recent insights into the importance of microbes in soil and ecosystem health warrants a better characterization of soil microbial communities’ response to S°. This study assessed the sensitivity of fungi and bacteria to S° amended alkaline soil in an arid region of a commercial vineyard in the southern Okanagan valley of British Columbia (BC). Using bacterial and fungal isolates collected on site, I tested their tolerance to both S° and concomitant changes to pH in a number of growth assays. In addition, I measured changes to soil bacterial and fungal communities following the addition of ~3000 kg of S° to acidify ~2 ha of commercial vineyard soil. Finally, I assessed microbial decomposition and aboveground plant diversity following S° application for functional analysis. I found that, while there is potential for S° and pH to impact microbial growth in my growth assays, S° application in the field did not significantly change microbial or plant community structure, and I observed no changes to organic matter decomposition in my system. Notably, S° application did not lower the pH of soil in my system, likely due to buffers present in the irrigation water. Other external factors such as S° particle size may have also impacted the timescale of S° oxidation in soil. Growers should consider these factors when using S° as an acidifier, fertilizer or biocide.