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

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. The region is well suited to organic production of blueberries, but the soils tend 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, with the exception of woodchips, banded on the soil surface. Soil samples were collected in September 2021 and 2022 and analyzed for a suite of soil health indicators and soil microbial community structure, including Soil pH, electrical conductivity, Total N, NH-N, NO-N, available P and K, soil organic matter, extractable organic carbon, active carbon, microbial biomass carbon, β-glucosidase enzyme activity, microbial respiration, and bacterial and fungal community structure and abundance. 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 year of the study 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.