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Organic Fruit Production

Melisa Lutz Blouin

The next time you bite into a crisp, tart, pesticide-free apple or savor locally grown, organic blackberries, spare a moment to think of horticulture professor Curt Rom.

Rom has studied fruit physiology at the University of Arkansas for 20 years. He started out as a product of the 1970s green revolution – “feed the world, save the world,” he says. But soon after he migrated into industrial fruit production.

When large grocery chains began gobbling up business, and food production became more industrialized and centralized in the 1990s, Rom watched many small orchards go out of business. But recently, concern about sustainability and the price of transporting foods long distances has launched a movement towards sustainable and organic agriculture. Organic orchards have sprouted, but producers lack the knowledge to create and nurture organic and sustainable growth. Rom and his colleagues hope to give farmers scientifically proven methods that will help their farms flourish.

 
Horticulture Professor Curt Rom shows his extended season berries.

“This combines my love of agricultural science and the environment,” Rom said. However, he emphasizes that he is not an organic evangelist.

“I’m not pro-organic or anti-organic,” Rom said. “I’m an agricultural scientist.” He wants to study this relatively unexplored field.

“In organic fruit production, there are a lot of questions to be answered,” he said. “There’s an opportunity to do research in an area where there is no research.”

Rom has traveled across the United States, Europe and Australia to study sustainable and organic practices implemented by fruit growers. He also has surveyed organic and sustainable fruit tree growers to determine challenges they face. He and colleagues formed the Southeast Organic Fruit Initiative Working Group, consisting of scientists, educators and extension workers, and they have conducted focus groups in five states in the southeast.

“Our goal is to have science-based technologies for growers who want to grow fruit organically,” he said.

Today, Rom and his colleagues have two organic and sustainable fruit production projects, each with its own challenges and emerging questions. The first one involves growing apples organically, and the second involves extending the growing season for organic blackberries and raspberries.

A New Philosophy

In a conventional orchard, growers eliminate the “competition” — ground cover or weeds — by using herbicides. But in an organic orchard, growers manage the interaction between the plants and apple trees.

In addition, growers need to provide sufficient nutrients to the plants. In conventional orchards, growers use water-soluble nutrients that feed the plant directly. But in organic orchards, growers enhance the biological activity of the soil so that it will, in turn, nourish the trees.

“We are looking at a completely different philosophy of plant management,” Rom said.

Ground cover potentially can eliminate competing weeds and nourish the trees. Rom and his colleagues used four different types of ground cover in the field – municipal green compost, wood chips, shredded white paper and mowed and blown vegetation. They also used three different types of nutrients -- a control group with mulch only, a group treated with composted poultry litter and a group treated with commercial organic fertilizer.

The orchard was established in the spring of 2006, with a disease-resistant apple variety called Enterprise that ripens in mid-September. The large, round apple is red with a green-to-yellow background. It has a tart flavor with a firm, crisp texture that makes it good for eating, cooking or processing.

The fruit was harvested for the first time in 2008.

“In my 25 years of research, I’ve never had an orchard that has grown so well and been so productive so early,” Rom said.

A Team Approach

“In organic, sustainable farming, everything is related to everything else,” Rom said. “In conventional orchards, people typically look at the short term. In a sustainable orchard, you are looking at a system that will last 10-20 years or longer.”

Examining what makes a sustainable orchard requires an army of researchers with various fields of expertise. Rom works with Don Johnson in entomology; Elena Garcia, an extension horticulturist; Jennie Popp, an agricultural economist; Mary Savin in crop, soil and environmental sciences; Terry Kirkpatrick in plant pathology; and soil chemist David Miller.

Even with all of this expertise, the scientists did not anticipate an unforeseen issue that cropped up in the orchard: Mice began eating the bark on trees. A conventional orchard has hard ground with no groundcover and thus has few problems with rodents. But in the organic orchard, mice found a haven where vegetation was mowed between rows of apple trees then blown beneath them for mulch.

To address this problem, researchers put up perch poles for red-tailed hawks, tilled the ground under the ground cover to destroy tunnels and nesting sites, and used box traps to capture the animals.

 
Jason McAfee checks the orchard's weather station.

Other issues that have cropped up include managing weeds and other pests, both of which require daily involvement from the grower. The researchers measure the probability of insect infestations by looking at weather conditions and other factors, and if the probability gets high, they will use organic pesticides to address the problem.

“We only spray when we absolutely have to and when we have evidence that it is needed,” Rom said. They also use weather models to help predict the possibility of disease. Irrigation is based on readings of soil moisture from instruments in the ground. When the soil moisture is sufficient, irrigation stops.
All of this adds up to vigilance on the part of the grower.

“You have to be much more nimble in an organic orchard to respond to changes in the system,” he said.

Another issue that crops up is knowing how and when to augment fertilization.

“For conventional systems we have very precise techniques,” Rom said. Effective timing of fertilization remains unclear in organic systems. Rom and his colleagues hope to optimize the timing of fertilization.

They have USDA funding for four years to address these and other challenges. The researchers also are working with a grower in Berryville to replicate the techniques they are using here. The funds also will support an apprenticeship, with the hope that the apprentice will become a local fruit producer.

Shifting Seasons

The second project involves beloved fruit with a short season: blackberries and raspberries. Working with horticulture professor and blackberry breeder John Clark, Rom wants to extend the growing season.

“We’re talking about doubling the season of cash flow for a farmer,” Rom said.

To accomplish this, the researchers built 12 “tunnels” with rows of raspberries and blackberries inside.  They hope to protect the plants from frost in winter and excessive heat in summer, allowing the fruit-bearing season to begin in May and extend through Thanksgiving. The usual season for these berries lasts from mid-June through early July.

They can do this in several ways: selecting the right blackberry breed, selective pruning, and building tunnels, which protect the flowers from frost, heat, thunderstorms and hail.

“This idea is suited to organic farming, because we are modifying the environment,” Rom said. “If we can shift production times, we change the relationship of insects to plants, providing more protection from pests.”

Two local growers have joined university researchers on the project. With help from Rom and his colleagues, they have built tunnels and planted blackberries and raspberries.

“It’s one thing to do it at a research facility. It’s another thing to do it on a working farm,” Rom said. “Growers come up with questions that we hadn’t thought of.”

Rom and his colleagues have made progress, but still have some distance to go to achieve their goals. Using the tunnels, they have shifted the spring berry-producing season by two weeks. Mild, cold springs in Northwest Arkansas have not produced enough heat energy in the tunnels to produce fruit earlier.

In the fall of 2007, berries grew continuously in the tunnels until Thanksgiving, whereas field production ended October 15th. But in 2008, a hard frost on October 24th caused significant damage to the fall crop.

While heat built up in the tunnels during the day, at night the temperature inside the tunnels hovered 1-2 degrees above the outside temperature. When the outside temperature plunged to 20 degrees, the plants suffered damage.

Rom finally found that polyester “frost curtains” combined with chafing dish burners raised the temperature in the tunnels about 10-15 degrees. Thus a 24-degree night would be close to 40 degrees in the tunnels.

“If the plants are kept above 32 degrees, they will be fine,” Rom said. Sub-freezing temperatures occur three to four times during March and April and three to four times between mid-October and Thanksgiving.

In addition to an extended harvesting season, the plants in the tunnels differ from those in the outdoor fields – they are taller, sport more flowers and produce bigger berries.

“Just the environment of the tunnel is changing the physiology and growth of the plant,” Rom said. Food science professor Luke Howard will examine the berries to determine if there are nutritional differences between the tunnel berries and the field berries, and Rom will focus on why those differences occur.

Regardless of what the studies find, citizens of Northwest Arkansas can enjoy the fruits of the researchers’ labor. Students from the student organic farming association help harvest the fruit and sell it at the Fayetteville Farmer’s Market.

“I had fresh blackberry cobbler last Thanksgiving,” Rom said. And that may happen for all of us one day soon, thanks to his research.

The researchers featured are all professors in the Dale Bumpers College of Agricultural, Food and Life Sciences with joint appointments in the University of Arkansas System’s Division of Agriculture.

Illustration by Eric Pipkin

Photos by Russell Cothren