Puyallup, WA | khills@wsu.edu

Karen Hills has been a Research Associate with Washington State University’s Center for Sustaining Agriculture and Natural Resources since 2018. She contributes to several projects involving re-use of organic materials. Karen developed her interest in the natural world during her formative years, which were spent in interior Alaska. She earned a B.S. in Rural Sociology from Cornell University, an M.S. in Soil Science from University of Vermont, and a Ph.D. in Crop Science from Washington State University. Karen’s areas of interest include sustainable management of soil and nutrients.

Session Code: A1

Track: Current Research (hosted by CREF)

Session Name: Impact of Soil Carbon and Water Dynamics

Session Time: Wednesday, Jan 25, 8:15 to 9:45 AM

Presentation Title: Understanding the Short- and Long-Term Soil Carbon Storage Benefits of Compost Application to Agricultural Systems

Presentation Description: Several recent policy developments in Washington State support soil health efforts and could lay the groundwork for increased use of compost and other soil amendments within agriculture. This is an important development given longstanding and ongoing efforts to increase organics diversion from landfills and put them to beneficial use after processing. However, it is still unclear whether soil amendments can contribute to long-term soil carbon storage, despite the fact they likely deliver crop growth benefits. This project, initiated by the State Legislature, analyzed existing data from organic amendment studies on agricultural lands, including dryland wheat systems, to quantify the carbon sequestration benefits in the diverse soils and cropping systems of Washington State. Following a single application of municipal compost, field data captured positive impacts on SOC at depth (to 90 cm) in drylands, suggesting potential for long-term C sequestration.  Given the short-term nature of many studies into soil health benefits of soil amendments, process-based models (DAYCENT, COMETFARM) were used to quantify temporal sequestration benefits from soil amendment and were useful to confirm beneficial application rates to achieve net-sequestration by 2050, and how these rates can differ between crop rotations. By combining short-term data and long-term projections, the work provides important insight into how compost may be routed for application in agricultural systems for soil health and carbon sequestration.

Session Code: E3

Track: Markets, Marketing and Uses

Session Name: Current Research: Value vs Cost, Urban Carbon Farm, Microplastics

Session Time: Wednesday, Jan 26, 4:15 – 5:45 PM

Presentation Title: Differentiating the Value and Cost of Compost Across Likely Farm Use Scenarios in Western Washington

Presentation Description: Similar to other urban and peri-urban areas across the U.S., western Washington has expanded municipal compost production over the last decade or more. However, demand from agricultural end users for this compost has lagged. To better understand the demand side of this relationship, this work compared cost reported by western Washington compost facilities with the potential value of compost in likely farm use scenarios for a number of different types of crops grown in western Washington. Scenarios were developed to determine the potential value of compost use in winter wheat, blueberries, raspberries, and direct market mixed vegetables. Compost cost including delivery and spreading was estimated at $27.05 per cubic yard. Compost value was less than cost for winter wheat and blueberry, while value exceeded cost for raspberry and direct market mixed vegetables. Under reasonable assumptions, the value of compost can exceed cost for some crops grown in the region. This study demonstrates that compost can have a wide range of values, depending on the cropping system to which it is applied, and the application rate needed to see impacts. Relevant to the discussion are potential changes to compost collection programs to improve the quality of compost (and hence improve its value to end users) and the potential of subsidies (for example, through shared spreading equipment) to increase demand from agricultural end users.