American Farmland Trust, Discovery Farms® Washington, King Conservation District, and Whatcom Conservation District worked together to engage producers in a cooperative, on-the-ground research and demonstration project to assess, promote, and improve adoption of on-farm conservation practices that enhance water quality in Puget Sound.

Working on two farm sites in King County, Washington, this project measured water quality, manure, and weather data associated with four different types of manure storage: a pile on dirt, uncovered; a pile on dirt, covered with a tarp; a pile in on a concrete slab, uncovered; and a pile on a concrete slab; covered with a roof.

Between October 2020 and May 2021, the project team measured soil samples from beneath the piles on dirt, stormwater runoff from the piles on concrete, manure composition from both, and tracked meteorological events. The project analysis focused on nitrogen, nitrate+nitrite, and phosphorous with assessment of fecal coliform, salinity, and sediment parameters.

Findings from the data analysis showed that covered manure has less runoff and leaching of manure nutrients, manure on a slab has no leaching to groundwater and can contain stormwater when designed properly, manure composition is reflected in the analyte profile seen in stormwater runoff, and covered manure achieves a greater temperature to enhance the composting process and create a better end-product. Additional research is needed to fully understand the soil and water quality impacts of different manure management strategies over seasons.