University of Maine graduate student Rafa Tasnim collects data at the University of Maine's Blueberry Hill Farm in Jonesboro. Photo courtesy of the University of Maine
BANGOR, Maine, Oct. 3 (UPI) -- In the wake of another dry, hot summer, small farmers who grow wild blueberries in Maine are searching for survival strategies, and researchers at the University of Maine are trying to help.
Temperatures are rising across Maine, especially in the state's Down East region, but researchers say that warming, on its own, isn't yet a problem for blueberries.
The problem is that high temperatures can increase the severity of droughts, drying blueberry fields and depressing yields.
"When the soil gets too dry, that's when rising temperatures become a big problem," Rafa Tasnim, a doctoral candidate in ecology and environmental sciences at the University of Maine, told UPI.
Over the last few decades, harvests have remained healthy for cultivated, or high bush, blueberries, which are easier to manage, but the same can't be said for wild blueberry fields -- the native bushes that yield Maine's iconic fruit.
"This year, we had lower yields than 2021, and in 2020, Maine literally had half the wild blueberry production than usual because of drought," Tasnim said.
Tasnim is one of several researchers at the University of Maine who are focused on understanding the ways wild blueberry fields will be impacted by climate change, as well as seeking to identify methods for safeguarding wild blueberries.
Studies conducted over the last few years have highlighted the importance of soil moisture.
"There are big pores in blueberry field soils, so even with irrigation, the soil drains really quickly," Tasnim said.
The largest blueberry operators -- big, international companies -- can afford the irrigation systems that relieve drought conditions, but most small, independent growers cannot.
"The group we are trying hardest to work with and help now are the folks who are not yet irrigating," Lily Calderwood, wild blueberry specialist and assistant professor of horticulture at the University of Maine, told UPI.
Some small blueberry farms have been able to get assistance from a program run by the Natural Resources Conservation Service, part of the U.S. Department of Agriculture, but funds are limited.
"Right now, the NRCS program only has $50,000 a year that can go to irrigation projects, so they often have to break up installation projects into phases, stretched across three years," Calderwood said.
"But these farms don't just need financial support. They also need technical assistance, because every field is different."
Ben Perrin, owner and operator of Burke Hill Farm, a certified organic wild blueberry farm in Cherryfield, doesn't think irrigation makes much sense for most small growers.
"Some of the big corporate companies and growers have buried irrigation pipes, but it's insanely expensive for small growers," Perrin told UPI.
To save money, smaller growers typically are forced to lay pipes above ground, but that means they have to be installed at the beginning of each season and then collected and stored at the end.
"I don't personally like to eat irrigated berries," Perrin said. "Irrigation just makes the berries taste like water."
Though rising temperatures have increased the risks posed by drought, Maine's weather patterns remain hard to predict.
"We have years that are way too wet and years that are way too dry, and they can be back to back," Calderwood said.
For farms that can't afford or justify the expense of a new irrigation system -- one they may only need once every few years -- soil amendments like biochar or mulch are essential, researchers say.
Biochar is a charcoal-like substance that's made by using heat to accelerate the decomposition of organic material, like forestry waste. Researchers say the pyrolysis process can be tweaked to ensure the biochar doesn't alter a field's acidity.
Wild blueberry fields must remain sufficiently acidic to keep the bushes happy and the weeds at bay.
"We have used biochar in the soil of our experimental blueberry fields, and what we observed is that the biochar helps the soil retain moisture," Tasnim said.
Unfortunately, the availability of commercial biochar is limited, leaving mulching as the most readily available solution.
"We're currently working to identify the ideal mulching depth and trying to determine whether whole-field mulching is worth the effort," Calderwood said.
Perrin said he does some mulching, but noted it's expensive and labor intensive.
"Personally, I have fields that are scattered around geographically, and that's for strategic regions," he said.
When a drought, frost or bad storm strikes, his geographical diversification ensures some fields will remain healthy, Perrin said.
To help farmers looking for additional safeguards, Tasnim and Calderwood are working to understand when exactly wild blueberries need moisture, so that farmers can deploy more targeted mulching or biochar applications -- whether just before flowering and pollination or right before fruit production.
"Preliminary research suggests during the fruit maturation period, right after pollination, that period is very critical for them, so they need sufficient water and nutrients or they will drop their fruits," Tasnim said.
Growers have begun to shift harvest times in response to climate change, Calderwood said.
"The season itself has become longer. We have an earlier spring and later fall, but the harvest time has gotten smaller," she said. "This season, for unirrigated fields, it ran from from between mid-July and mid-August. Peak quality berries lasted only about three weeks."
Calderwood tells the farmers they need to be ready to harvest sooner.
But researchers are somewhat limited in the guidance they offer blueberry growers because many potential threats posed by climate change aren't well understood.
"With the changing precipitation and rising temperatures, as well as increases in humidity, all those factors are affecting plant pathology patterns in Maine, which can have a significant impact on blueberry production," Tasnim said.
Because wild blueberry bushes aren't planted and have never been bred, they do have some advantages that cultivated crops don't -- genetic diversity.
"In some ways, that makes them more resilient," Calderwood said. "There can be 1,500 genetically distinct individuals in any given field. It truly is an ecosystem that we are trying to work with and preserve."
Though some of Maine's wild blueberry fields may continue to flourish for decades, Perrin said the industry is on the way out, with production shifting north of the border.
"The biggest thing with climate change is that Canada is going to take over," he said. "With a few degrees of warming, fields that were once too risky to invest in because of frost are not getting that frost anymore."
Milder temperatures, stronger government support and a favorable exchange rate have fueled a rapid increase in wild blueberry production in Canada, Perrin said.
"And I don't think it's coming back," Perrin said. "I think the Maine wild blueberry industry has maybe 10 to 15 years left and it will be a gone industry."