Sapphire-colored blueberries; midnight-colored blackberries; raspberries in shades of red, ginger, and purple; and that oh-so-brief flash of scarlet strawberries, Oregon’s first-of-summer berry.
Aurora’s experiment station thrives on the sensational world of berries—that crowd-pleasing “superfood” bursting with nutritious antioxidants and bright, complex flavors.
“I simply love working with berries,” said Bernadine Strik, OSU’s statewide berry specialist and berry research leader at OSU’s North Willamette Research and Extension Center (NWREC). “Each one is different. It’s interesting and challenging at the same time. It’s never a boring job.” Since she started working for OSU in 1987, Strik knows the farm stories of the grandmothers and fathers, granddaughters and sons of dozens of growers. Long-standing relationships with Oregon’s berry industry contribute to the success of her research.
Production and fruit quality
OSU research has changed industry practices. For example, OSU researchers found that blueberry plants placed at high density (1.5 to 3 feet apart in the row) produced 72 percent greater yield over a 6-year period of production compared to the traditional 4-foot, in-row spacing. Now, most growers plant blueberries closer together. Research also showed that a simple trellis improved machine-harvest efficiency by as much as 8 percent of total yield. Now almost all blueberry fields use this simple trellis. “Some growers will say, ‘We’ve always planted them this way,’ and they don’t realize that the research came from OSU and is now standard practice,” Strik said.
OSU’s research has helped increase yields, lowered labor costs, and boosted the bottom line for Oregon’s berry growers. Small fruits and berries contributed nearly $160 million in sales to the state’s economy in 2012, according to Oregon’s Agricultural Information Network. OSU’s research focuses on improving organic and conventional production systems, better pruning techniques, machine harvesting, fertilizer use, irrigation practices, and more.
Now imagine a delicious blackberry pie served with a dollop of midnight-stained ice cream, a favorite summer treat. Marion blackberries grow in black clumps on green stems with prickly thorns. The thorns can fall off as the machines harvest the berries, ending up in the final product. “If thorns end up in your pie, that’s a potential liability,” Strik said. That’s not an option for growers. So OSU developed a method to brush blackberry fields in the winter. To do so, Strik worked with Littau Harvesters in Stayton, Oregon to customize a harvester machine by adding rotating brushing heads instead of standard rotary heads. “We determined brushes work best and can reduce potential contamination from thorns as much as 70 percent,” Strik said. “Now, more than three-fourths of the commercial Marion blackberry acreage is brushed every winter. We not only reduced contamination from thorns—we developed a whole new business.”
The promise of organic blueberries
In a unique organic test plot, an acre of blueberries grows on raised beds and flat ground. Blueberries are also grown with mulches comprised of sawdust, compost, or black landscape fabric to test ways to manage weeds. Recorded shrieks of hawks play repeatedly to scare off birds that would nibble on the treats. On a warm summer day in their seventh year of life, these blueberry plants flourish. Few places match Oregon as an extraordinary production region for blueberries. “Oregon is an ideal place to grow blueberries and blackberries organically. The reason is the Mediterranean climate,” Strik said. The dry summers reduce weeds and disease problems and mild winters make winter cold-damage to plants relatively rare. These picture-perfect growing conditions make for excellent yields of high-quality fruit.
Research at the Oregon Tilth-certified test plot is helping those farms become more productive. Research found that plants yielded better when grown on raised beds, fertilized with a low rate of fish emulsion or a high rate of feather meal fertilizer, and when mulched with weed mat or compost topped with sawdust mulch. The costs to manage weeds were much lower when weed mat was used than with any other mulch. From 2008–12, plants grown on raised beds had an average 27 percent greater yield than flat ground, according to Strik. “We’ve found that when using certain organic production treatments, yield was very similar to conventional berries,” Strik said. “What’s important to recognize is that the costs are higher in organic production systems. It’s more expensive to buy these organically approved fertilizers and to control weeds. But the growers get a higher price for organic blueberries than conventional blueberries. The good news for consumers is that because of OSU research, organic blueberries can be grown more economically.”
The Oregon Blueberry Commission, the Northwest Center for Small Fruits Research, and the Washington Blueberry Commission and federal grants fund the research.
Growing blueberries more like trees
Neighboring the organic blueberry research plot, OSU experiments with a different kind of blueberry. It has a tree-like, taller profile, rather than the traditional shorter bush. White, tube-shaped plastic protects the rootstock trunks. They are managed as conventional agriculture. A whole block of them spreads across a field at the experiment station. Wei Yang, OSU Extension horticulturist at NWREC, is experimenting with grafting a few different blueberry varieties onto undomesticated blueberry tree rootstocks from eastern Texas, Oklahoma, and Florida. “One advantage to a blueberry tree is reducing machine harvesting loss of fruit,” Yang said. “Another advantage is that you can grow grafted blueberries in a relatively high-pH soil. It also has better drought tolerance.” It’s a five-year project funded by the Oregon Blueberry Commission and USDA’s Specialty Crops Research Initiative.
The USDA’s Agricultural Research Service collaborates with OSU in a small fruit-breeding program that has reaped benefits for growers and consumers for almost a century. The USDA’s berry crop breeder, Chad Finn, makes the important decisions on which parents to use in crosses, and when an advanced selection is ready to become a new cultivar. Strik lends her technical expertise to growing these in typical production systems at the station and learning more about how growers might best be able to manage these new cultivars once they are released. Potential varieties of blueberry, blackberry, red and black raspberry, and strawberry are evaluated in the field at the station.Only the juiciest, best berries are plucked from these trials. Promising advanced selections are appraised at the station for traits the industry wants, like disease resistance and ease of machine harvesting. Growers are involved at many steps of the process, including field days, where they sample new strawberries, red and black raspberries, blackberries, and blueberries in tastings, learn about the latest research, and ask researchers questions.
The program has released eight new strawberry cultivars, five genetically thornless blackberries, seven trailing blackberries for the fresh market, two primocane-fruiting raspberries, two summer-bearing red raspberries and two blueberries. Many of these varieties are well known to Northwest berry lovers—the ‘Tillamook’ strawberry and the ‘Black Diamond’ and ‘Obsidian’ blackberries may ring bells. In 2012 alone, the Pacific Northwest saw $17 million from sales of fruit and nursery plant varieties developed by the program, according to data collected by wholesale nurseries and the Oregon and Washington Agricultural Statistics Service.
Organic blackberries, too
In other organic ventures, OSU has the only certified organic blackberry research plot in the world. This 1-acre field is only three years old. “It will take a couple more years to see the impact of the production methods that are being studied, but the results so far show a lot of promise for organic systems for blackberries,” Strik said. Wires support the plants’ growth on a trellis system. Half of the stems from one plant are woven around two wires in one direction and the other half in another direction. A plant towers 6 feet high. All are set 5 feet apart in the row.
Here, Strik and her colleagues study weed management using weed mat, hand hoeing, and not weeding some plants at all. They are looking at fertilizing with hydrolyzed fish or corn steep liquor, a byproduct of the wet milling of corn. Some plants are irrigated after harvest while others are not. This work is being done on the two most important processing blackberries in Oregon—’Marion’ and ‘Black Diamond’. All are machine harvested. Researchers are investigating plant growth, the amount of nutrients the plants take up, yield, weight and firmness of fruit, fruit quality, flavor, diseases and weeds, and much more. “Oregon is the largest processed blackberry production region in the nation. But the availability of organic processed blackberries is a huge barrier,” Strik said. “We want to know if we can help growers economically produce organic blackberry fruit for the processed frozen fruit, juice, or purée markets ultimately destined for jams, yogurts, baby food, or organic blackberry ice cream. It’s exciting to open up the possibility of new markets.”
Expanding the reach of berries
What does all this mean for you as a fan of sweet, nutrient-rich berries? You’re at the farmers market and pass your favorite berry grower. But wait—it’s late September. Rosy raspberries leave streaks of bright crimson juice staining green containers. You touch that succulent fruit, reminded of the anticipation of early summer.
Not only have Strik and other researchers studied how to improve machine-harvesting efficiency, increase yields, and reduce pests and weeds, Strik has studied options for extending the season for various berries. Options include perpetual fruiting day-neutral strawberries—instead of fruiting only in the month of June, these plants fruit from May through early October. When growers use tunnels or row covers to keep the plants protected from rain, they can pick high-quality fruit, destined for fresh market, earlier and later in the growing season.
Who knew strawberries could be pruned? Just by mowing two to four weeks after the last harvest of June-bearing strawberries, growers can increase yield by 20 percent compared with mowing right after harvest or not mowing at all. It’s a practice growers have adopted, Strik said. She and her graduate students have studied how much nitrogen fertilizer different berries need and the best time to apply the fertilizer—the goal has been to maximize plant uptake and yield and to minimize any possibility of groundwater contamination. Growers have found this research very helpful. Present work looks at other types of nutrients. Overall, research is focused on how to grow berries better.
That means more berries. “Consumers are seeing more strawberry, blackberry, raspberry, and blueberry fruit available and a much longer season. Expect Oregon berries from May to October for many of these crops,” Strik said. And that’s good news for berry fans.
In addition to the ongoing work on organic production systems for blueberries and blackberries, Strik and her team are working with colleagues to better understand root growth in these crops. How deep in the soil are the roots located, at what time of year do they grow, and how long do they live? These are important questions to answer in order to better manage fertilizer. Along with a good understanding of nitrogen fertilizer management, current work focuses on the plants’ requirements for all nutrients, like phosphorous, potassium, and calcium, among others. Work is under way to help growers better understand how to measure plant nutrients for different berry types and cultivars, and how to adjust fertilizer accordingly.
Research is also under way to determine how fruit quality (sugars, acids, firmness, and fresh and processed quality) is affected by methods of producing berries. “Oregon growers are known for producing very high-quality berry crops, and it’s very important to our industry to continue to do so,” Strik said. “When we work with growers to develop or modify production systems, we always look at the economic returns, considerations such as labor costs, yield, and quality.”