Building Soil Health Resiliency Through Vermicompost Tea Application: Final Report

This final report evaluates the effects of vermicompost tea (VCT), a byproduct of vermifiltration wastewater treatment systems, on soil health, microbial communities, and onion production. The project investigated microbial processes within a dairy vermifilter system in central Washington and assessed how VCT application influences soil biology and crop performance under greenhouse conditions.

Vermifilter samples collected across seasons were analyzed for key nitrogen cycling genes, confirming the presence of functional microbial communities. In controlled greenhouse trials, Walla Walla sweet onions grown in soils treated with vermicompost tea produced greater bulb mass compared to those treated with a conventional synthetic fertilizer. Microbial sequencing revealed shifts in community composition across treatments and over time, with nitrogen- and carbon-cycling taxa prevalent in VCT-treated soils.

These findings suggest vermicompost tea may enhance soil biological activity and support crop productivity while advancing sustainable manure management and circular waste systems in agriculture.