Organic blueberry growers can improve their bottom line by planting in raised beds, using a plastic weed mat for mulching and lower rates of fertilizer, according to research from Oregon State University.
Bernadine Strik, OSU berry crops professor, led a 10-year study to determine best management practices for organic blueberries, which was recently published in the journal HortScience.
More than half of all organic blueberries grown in the U.S. come from Oregon and Washington, Strik said. The Oregon Blueberry Commission initially funded her project in 2006, looking for additional support in organic production.
“The market is very strong for organic fruit specifically from the Pacific Northwest,” Strik said. “We have such a good climate for growing organic blueberries.”
At the time, just 2 percent of the region’s blueberries were certified organic. The total now is as high as 20 percent, making the Northwest the largest producer of organic blueberries in the world.
“I don’t see that changing,” Strik said. “I think that’s a real advantage to our region.”
Strik conducted her study at the university’s North Willamette Research and Extension Center in Aurora, planting two varieties of blueberries — Duke, an early season berry, and Liberty, which ripens later in the year.
Strik also had the 1-acre field certified by Oregon Tilth, ensuring she would face the same challenges as organic growers with record keeping and inspection.
“This was my first certified organic study,” Strik said. “And it’s still the only certified organic blueberry research trial in the world.”
Over the course of a decade, Strik found that Liberty blueberries yielded 22 percent higher in raised beds versus flat ground, which has proven to be a no-brainer move for organic and conventional growers alike.
As for weed control, Strik looked at a few different options for organic growers, including sawdust mulch, yard debris topped with sawdust and a black plastic weed mat.
Though it did carry some drawbacks, such as increased soil temperature and field mice, the mat proved to be the lowest cost option. Sawdust mulch cost nearly twice as much, Strik said, and almost three times as much for the sawdust and yard debris combination.
“The higher cost was because there were more weeds that needed to be pulled,” Strik said.
Finally, the study looked at organic fertilizers, which can cost 10 to 20 times as much as conventional products. Strik applied both a feather meal and liquid fish at rates ranging from 25 to 65 pounds per acre on the low end, and 50 to 125 pounds per acre on the high end.
Liberty berries showed little difference between the low and high rates of fertilizer, Strik said, indicating a huge cost savings to organic growers. Duke berries, meanwhile, fared best with higher levels of cheaper feather meal, and were especially sensitive to liquid fish. Strik suspects that has to do with higher levels of potassium.
Bryan Ostlund, administrator of the Oregon Blueberry Commission, said growers are seeing more acreage being planted or converted to organic statewide, and Strik’s research gives growers the tools they need to be successful.
“It’s a highly competitive market,” Ostlund said. “Growers are always asking questions, trying to increase those yields.”