Jun 22, 2009
Tunnels Take Advantage of Off-season Markets

About 90 people went to a field day at North Carolina State University’s Piedmont Research Station in May to see what researchers there have learned about growing strawberries under high tunnels.

The field day audience observed strawberry plants that had been planted the previous September and were still bearing in early May. It was an eye-opening experience for everybody, said Barclay Poling, professor of horticultural science at NCSU.

“We’re growing berries in the typical off-season for strawberries in North Carolina,” said Andy Myers, the station’s crops research operations manager.

The ultimate goal of the high tunnel research is to show North Carolina farmers how to grow a consistent supply of strawberries in late fall, winter and spring so they can take advantage of those off-season markets, Poling said.

In spring, for example, field-grown berries in North Carolina typically aren’t ready for harvest until after Easter, while tunnel-grown berries can be ready before Easter, he said.

“The tunnels are giving us at least a one-month jump.”

And the tunnels continue bearing into June, Poling said.

There are six Haygrove high tunnels at the station, located in Salisbury in the western side of the state. All of the tunnels are 150 feet long and 24 feet wide. Four of them are devoted to strawberries and two to cane berries, Myers said.

The tunnels were erected in September 2006 and have been bearing fruit for about three years, said Jim Ballington, NCSU professor and small fruit breeder.

More North Carolina growers are using tunnels these days, whereas a few years ago nobody was using them. Positive data from NCSU’s high tunnel experiments could certainly encourage that trend, Myers said.

He knows a grower who sold tunnel-grown strawberries in December for $18 a gallon. That’s about double the typical price local growers get for field-grown strawberries from late April to mid-June, Myers said.

Selling local strawberries during the Thanksgiving and Christmas markets presents a huge marketing opportunity, Ballington said, but marketers need to find a way to help consumers differentiate between field-grown berries and tunnel-grown berries, which generally are of a higher quality.

“The public needs to recognize the superior quality and pay more for it,” he said.

Spring and fall yields are much higher under the tunnels, and the resulting fruit’s shelf life is much longer. There also is not as much disease pressure under the tunnels, which help protect the plants from frequent rains, Ballington said.

Ballington, who works at the NCSU campus in Raleigh, was the first to discover that Strawberry Festival – a University of Florida variety – was highly adaptable to the Piedmont Research Station’s high tunnel system. Ballington was looking for varieties that produced well in fall, winter and spring. Strawberry Festival and Sweet Charlie met those requirements, but Sweet Charlie’s fruit is softer and not as attractive as Strawberry Festival’s, he said.

Strawberry Festival gets off to a quick start in the Salisbury region, aided by a high elevation and mild winters. It’s ready for planting by mid-September in a tunnel and by early October in the field. Floating row covers in the tunnels trap heat during the day, which helps keep the plants warm. Water is supplied by drip irrigation, Poling said.

There are four rows of strawberry plants inside each tunnel, with each plant yielding about 3 pounds of berries per year. Poling would like to add a fifth or sixth row in each tunnel to increase productivity, even though they’d have to crunch aisle space to do that. The higher yields would help justify the extra expense of growing under tunnels, he said.

Ballington said the initial cost of high tunnels is significant, but so is the potential payback. He’s studying cost and return data with an economist as part of the research. He’d also like to test a new variety from University of Florida and compare its performance to Strawberry Festival.




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