UACES Facebook Going long on berry season with high tunnels
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Going long on berry season with high tunnels

By Dave Edmark
The Cooperative Extension Service
U of A System Division of Agriculture 

Fast facts:

  • Extended berry season can lead to larger yields and profits
  • Tunnels can be screened to keep pests out
  • Organic berries perform better in tunnels than field

 (1,199 words)

FAYETTEVILLE, Ark. – Blackberry, blueberry and raspberry farmers can potentially reduce their risk for crop loss and enhance their opportunity for cash flow by planting “under cover.” They can extend their growing season by raising their berries in high tunnels – and in some cases, tunnels within tunnels.

“Tunnels are a real opportunity for growers to extend their season, protect their crop and enhance their cash flow,” said Curt Rom, University Professor of horticulture in the University of Arkansas System Division of Agriculture.    “Tunnels fit into a production system and really complement traditional field production systems.” 

Eric Riddick of the USDA Agricultural Research Service releases C-Mac ladybugs in a screened blackberry high tunnel to control aphids. (Photo by Dave Edmark.)

A Division of Agriculture team led by Rom – including agricultural economics professor Jennie Popp, entomology professor Donn Johnson and horticulture Professor Elena Garcia – recently wrapped up a three-year study of high tunnels in search of ways to broaden the harvest season for berry growers. They were working under a series of grants from the U.S. Department of Agriculture National Organic Program, the Organic Farm Research Foundation and a current project funded by the USDA Southern Sustainable Agriculture Research and Education program.

The researchers realized that tunnels are gaining interest and popularity among American berry producers. They are being used extensively now for berry production in western states and the momentum is growing in Arkansas.

Previous studies on tunnels and berries had been done in northeastern states, where the issue was enabling the crop to survive the winter. Rom noted that’s not an issue in Arkansas; extending the harvest season and protecting the crop are the issues here.

 Timing is everything

In Arkansas, blackberries and blueberries have narrow harvest seasons, generally from mid-June to early to mid-July. Producers spend a year or more growing for a narrow harvest window. The timing has a financial impact.

”In Arkansas, when blackberries are ripe, everybody has blackberries,” Rom said. “You run into your typical supply-and-demand problem: with a high supply, the price went down.”

So the researchers considered using high tunnels to force the spring berries to be ready for harvest by mid-May. “We’re trying to take a four-week season and make it into a six-week season,” Rom said. “We’ve been successful at that.”

The tunnel-in-tunnel concept offers another way to further extend the season. Within the large main tunnel, producers can install an additional smaller tunnel to provide a second layer of cover that protects the plants from frost and increases heat during late winter. The tactic also advances the harvest. Berry plants inside the “tunnel-in-tunnel" can be advanced by five weeks and the main tunnel can advance the crop by three weeks ahead of the schedule for field plants. What was a three-week production season can effectively become an eight-week season.

Rom said farmers might put 10 to 25 percent of their production into the tunnel-in-tunnel option and start their market early. “You have to ask a higher price for those products,” he said. “The supply is low and demand is always high. So we hope you get a better value for your blackberries early in the season. The early crop gets a higher price than the mid-season crop.

“With the tunnel-in-tunnel, there’s added cost. But if we have a higher price to pay for that, there’s value. If a farmer can start selling products in mid-May, they’re extending the cash flow season so they can pay the bills and pay back the bank.”

Building and operating a high tunnel has added costs for a producer, but those costs can be offset. Inside the tunnels it’s possible to grow larger plants and yields about 15 to 20 percent greater than in the field. The economic model, Rom explained, is that if producers can get larger yields and sell them at a higher price, then they can justify the tunnel’s cost.

“If you want to pay for the tunnel in one year, you have to sell the berries at a very high price,” Rom said. But the berries will produce well for five to seven years. Over that period of time, the cost of building and operating tunnels becomes profitable with increased yields.  

Organic opportunity

The researchers also found that tunnels provided opportunities for organic production of berries, which can bring a higher consumer price with a premium of 20 to 30 percent (and which also helps pay tunnel costs). In the self-contained environment of the tunnel, organic management is easier partly because the lack of precipitation enables natural-compound pesticide sprays to eliminate most disease threats.  

"When we use organic pesticides in the tunnel, we know that the pesticide will last two to three times longer than in the field because we’re not getting the dew, we’re not getting the precipitation, we’re not getting the wind, we’re not getting the light,” Rom said. “So when we have to apply pesticides, they tend to be more effective in the tunnel.”

Tunnels actually enable organic berry growing in Arkansas that would be nearly impossible in the field because of the presence of a new insect that arrived about five years ago, the spotted wing drosophila. There isn’t an organic insecticide available to use against the pest in the field that provides complete control.

“In a tunnel, Dr. Johnson has shown that we can put screens on it and exclude the insect,” Rom said. “So now we don’t have to use any insecticide and we don’t have the insect. In the field, we had 100 percent insect damage and essentially none in the tunnel.”

Rom has noticed that Arkansas growers are becoming more interested in tunnels. The spotted wing drosophila has had a negative impact on organic berry producers in the state, but most haven’t moved to tunnels yet. That might be changing.

“I think we’ll see more and more from the amount of inquiries we get,” Rom said, noting that small-scale farmers are usually cautious about taking on new technology. “Our field day and workshop we had this spring was packed. When we hosted the National Association of Blackberry Growers in February, the interest in our tunnels was huge. We probably had growers from across the U.S. come out to look at our tunnels to see what Arkansas was doing.”

To assist berry farmers in learning about tunnels and other aspects of production, the research team worked through the Division of Agriculture Center for Agricultural and Rural Sustainability to publish an 80-page handbook, Sustainable Blackberries and Raspberries. About 100 copies of the first version have been distributed to farmers and a second version is in progress. The handbook includes a berry production sustainability checklist that enables growers to score themselves and determine how well they’re handling about 150 aspects of managing berries. 

"The reviews we’ve received are comments like ‘Wow,’ ‘Thanks,’ ‘We needed this,’ and ‘First of its kind.’ As far as we know this is the first sustainability workbook in our part of the country. We just started distributing it this spring so we will probably get more reviews as growers have used it toward the end of this season,” Rom said.

Tunnels further enhance the opportunity for sustainable and organic crop production in Arkansas. “This is a technology whose time has arrived to help our farmers and support our food system,” said Rom.

The University of Arkansas System Division of Agriculture offers all its Extension and Research programs and services without regard to race, color, sex, gender identity, sexual orientation, national origin, religion, age, disability, marital or veteran status, genetic information, or any other legally protected status, and is an Affirmative Action/Equal Opportunity Employer.   


Media Contact: Mary Hightower
Dir. of Communication Services
U of A Division of Agriculture
Cooperative Extension Service
(501) 671-2126

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