Evaluating locally available organic amendments to enhance soil health indicators for highbush blueberry production east of the Cascades in the U.S. Pacific Northwest

Authors: SINGH, SHIKHA - Washington State University; LUKAS, SCOTT - Oregon State University; RETANO, ANDREA - Oregon State University; Bryla, David

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/3/2025
Publication Date: 7/1/2025
Citation: Singh, S., Lukas, S., Retano, A., Bryla, D.R. 2025. Evaluating locally available organic amendments to enhance soil health indicators for highbush blueberry production east of the Cascades in the U.S. Pacific Northwest. Scientific Reports. 15. Article 20933. https://doi.org/10.1038/s41598-025-05761-z.
DOI: https://doi.org/10.1038/s41598-025-05761-z

Interpretive Summary: Nearly 20% of the total production of blueberries in the United States is located east of the Cascade Mountain Range in Washington and Oregon. To produce blueberries in this region, growers must amend the soil with costly organic materials such as wood chips. Less expensive, locally available alternatives are needed in order for these growers to remain competitive. In cooperation with faculty and students at Oregon State University, an ARS scientist in Corvallis, OR determined that grape pomace compost improved soil health and resulted in higher soil nutrient availability than other amendments, including wood chips and biochar. Once it was incorporated into the soil, grape pomace compost also increased plant growth and fruit production relative to the other treatments. Therefore, grape pomace could serve as a viable amendment for blueberries, especially since it is low-cost and readily available from many wineries in the region.

Technical Abstract: While Oregon and Washington contribute approximately 60% of the total production of blueberries in the United States, there is still potential for growth on the east side of the Cascade Mountain Range in both states. While the region is well suited to organic production of blueberries, the soil tends to be sandy and low in organic matter. Currently, organic inputs used in blueberry systems are expensive and difficult to source in the region. Therefore, easily available alternatives that can foster productivity at a lesser cost are needed. An organic blueberry field trial was established in 2021 at Oregon State University’s Hermiston Agricultural Research and Extension Center to evaluate four organic amendments, including biochar, grape pomace compost, grape pomace co-composted with biochar, and woodchips (grower standard), each of which were either incorporated to a depth of 0.2 m or, aside from woodchips, banded on the soil surface. Soil samples were collected in September 2021 and 2022 and analyzed for a suite of soil health indicators, including soil microbial community structure. Results showed that incorporated compost resulted in higher soil organic matter, increased nutrient availability, and greater microbial activity than the other treatments. However, none of the treatments had any effect on the structure of the bacterial community, which by the end of the second season was largely dominated by Acidobacteria, or on the structure of the fungal community, which in both years was dominated by Ascomycota and Mortierellomycota. Data collected from this study will help us understand the suitability of organic inputs to enhance soil health indices while improving resource use efficiency.