Columbia Basin Blueberry Research Looking at pH

Blueberry growers in the Columbia Basin may be able to avoid waiting a year for soil to acidify before planting if all goes well in a research project launched this year by an Oregon State University Extension horticulturist in Hermiston.

Scott Lukas, OSU Extension horticulturist

The three-year project, funded by a grant from the USDA Organic Transitions Program, is looking at different ways to meet nutritional needs of blueberry plants and acidify the high pH soils common in the Columbia Basin, as well as trying to answer whether current practices are optimal for the regions’ blueberry production.

“We are looking at nutrient management under the lens of acidification,” said Scott Lukas, OSU Extension horticulturist.

Several factors led Lukas to delve into the project, including that conventional and organic blueberry production in Eastern Oregon’s Columbia Basin tend to experience what he calls pH creep, where the pH in soil increases to unacceptable levels as nutrients are added, and that little research has been done on existing practices.

Under current practices, Columbia Basin growers typically apply sulfur prills on acreage designated for blueberry production to bring down the pH and then wait nearly a year before planting. Lukas is looking at twelve different treatment scenarios in part to see if there might be a viable method to reduce that down time, as well as avoid the long-term pH creep, yet still help plants meet their nutrient needs.

“We are approaching this from a few different ways. We are looking at different methods of applying sulfur, different compost that could be used to increase soil organic matter and looking at biochar,” he said. “We’re hoping that there is a long-term strategy to keep that pH down and then make it so you don’t have to wait that year for the pH to be reduced.”

Lukas noted that blueberry plants prefer a pH level of around 4.5 to 5, but pH levels in the soils of Oregon’s Columbia Basin tend to average around 7.5. In addition, Columbia Basin soils tend to have low organic matter, Lukas said, typically less than a half of a percent. “It is kind of the opposite of what you are looking for,” he said of local soil conditions. “The nutrient management out here is a challenge, and keeping the pH in your target range is really difficult. But after pH and organic matter ranges are correct, blueberries thrive in the region’s well-drained, sandy soils.”

Among objectives, the research is looking to see if injecting micronized sulfur might be a viable alternative that can bring down pH more rapidly than existing practices, thus reducing the down time prior to planting; the research is looking to determine if growers need to apply acidified water to blueberry acreage; and the research is looking at whether a grower could potentially plant a field at a higher pH and reduce it over the course of time.

If nothing else, the research is expected to help quantify the efficacy of current practices.

“Most of this has not been evaluated through research,” Lukas said. “There is just this standard process that growers have developed over time that works well, but there hasn’t really been any research to update, support or complement current practices. There is always room for improvement and we hope to make Columbia Basin blueberry production as successful as possible.”