Tunnel Vision

08/01/2009 02:00:00 AM

By Tom Burfield

When grower Timothy Bradford plants bell peppers in an open field on his Isola, Miss., farm, an early frost can bring his fall deal to a halt as early as the first week of October, and he can’t plant his spring crop until after mid-April.

Now, thanks to a high-tunnel growing structure that he built last year, he can harvest bell peppers as late as December and do his spring planting in February.

Photo courtesy of the Mississippi Agricultural and Forestry Experiment Station

Tunnels or hoop houses are tent-like structures made from plastic stretched over a skeleton. They trap daytime heat and minimize the amount lost during the night.

High tunnels—or hoop houses, as they’re sometimes called—have been around for years. But the need for growers to enhance their profits in a down economy coupled with the current consumer craving for locally grown produce has sparked a resurgence.

“Growers are trying to figure out how they can produce high-quality produce, sell it locally, direct market it and get the highest price they possibly can,” says Bob Hochmuth, multi-county Extension agent for the University of Florida at the North Florida Research and Education Center in Live Oak. “This whole plasticulture technology fits into that perfectly.”

Tunnels are tent-like structures made from layers of plastic stretched over a skeleton often made from PVC pipes. They trap daytime heat, minimizing the amount that escapes at night, says Bill Evans, assistant research professor and research coordinator at the Mississippi State University truck crops branch in Raymond.

Tunnels are most valuable around the first frost in fall and just before the last frost in spring, he says. They’re similar to greenhouses, but they don’t have fans or heaters, and they don’t need electricity or gas.

“The one utility that they must have is irrigation,” Evans says. They typically use a drip system.

Hoop houses use the same type of equipment you would use in a field—a standard mulch layer, bed shaper and a small, single-row tractor.

The sides can be rolled up for ventilation, and the end walls open up so the tractor can get in. Evans recommends sides that can be lifted at least 4 feet—8 feet is ideal.

Any crop that can be grown in a field can be grown in a tunnel, Evans says, but growing in a hoop is more expensive, so it’s important to consider return per square foot. He recommends planting high-value crops, such as strawberries or bell peppers rather than sweet corn or pumpkins.

You’ll need “a nice, open piece of ground” that is well drained and unimpeded by a tree line that can interfere with ventilation, Evans says. Don’t put your tunnel at the bottom of a hill where cold air collects.

Growing project

Roberts Family Farms in Layton, Utah, started growing tomatoes in tunnels three years ago and added strawberries this year, says partner Tyson Roberts.

There are differences from growing in a field, he says. For example, fertilization requirements for the tomatoes are different, mildew and fungus can be a problem if you don’t allow for ample ventilation, and lack of air movement can hinder pollination.

“We learned that the hard way,” Roberts says. This year, he left the doors of his tunnel open for a few hours every day to enhance pollination.

Roberts built two fairly permanent steel structures, each 30 by 65 feet, for $1,300 apiece. You can buy kits for $2,000 to $10,000, but a neighboring farmer sold him the parts from tunnels he had taken down.

One advantage of the hoop house is that it allows you to gain customers in early spring and keep them through the fall, Roberts says. He can charge up to $3 per pound for tomatoes at farmers markets early in the season.

Grower Bradford raises high-value red and yellow bell peppers in his tunnel.

He has 20 years experience with greenhouses, but he added a 30- by 50-foot high tunnel to his operation last year.

Bradford paid $3,000 for the frame and plastic covering, and took in an extra $3,000 to $4,000—minus about $800 for labor and expenses—by extending his growing season.

He plans to build another this fall, if he can find the time. Eventually, he may convert the tunnel to a greenhouse.

A help for small farmers

Tunnels are especially beneficial for small-scale growers who do direct marketing and are looking to expand their growing season and the range of products they can grow, says Brent Black, Extension fruit specialist for Utah State University in Logan.

Black has had good luck with strawberries, some success with raspberries, and he is experimenting with blackberries, which are “marginally hardy in our climate.” Colleagues are looking at items, such as lettuce, spinach, chard and bok choy.

They grow in steel-framed structures about 90 feet long and 24 to 30 feet wide that cost from $2,000 to $4,000, depending on factors, such as how sturdy they are and how much ventilation they offer.

Although some growers in north Florida rely on high tunnels, the number of hoops in that state is not as high as it is in some areas because of the short transition period from cold weather to hot and vice versa—the time when the tunnels would be most valuable—Hocmuth says.

Nevertheless, some Florida growers do produce early-season vegetables, such as tomatoes and bell peppers in hoops, he says. And, by using a combination of tunnels, greenhouses and shade houses, some have quadrupled their production, sometimes growing 12 months of the year.

Grower beware

There are some caveats to keep in mind before embarking on a tunnel program.

If you’re used to growing on a large scale, switching to tunnels requires a different mindset, Black says.

“This is intensively managing a small area to maximize what you can produce there,” he says.

Be sure you have adequate labor available and a marketing window for the crops you plan to produce.

“Don’t grow (in a tunnel) when you’re doing another labor-intensive crop or when you can’t capture demand for out-of-season produce,” Black advises.

Evans concurs. If the farm stand or farmers market where you typically sell your produce closes after Halloween, you may not have an outlet for your product.

There’s plenty of room for growers during the “shoulder seasons,” he says. And a tunnel program can be very rewarding because you can produce a quality crop, and you’re not overwhelmed by a large expanse of land. On the other hand, don’t plan to take off holidays or weekends.

Unlike open fields, a tunnel needs to be checked every day, Evans says. “It’s not for everyone.”

TUNNELS ON THE MOVE

Photo by Ed Page, Colorado State University

Ed Page’s movable tunnel costs $4.50 per square foot if used over one plot but only $1.25 since he uses it over four or five.

Ed Page has taken the high-tunnel concept to the next level.

Growers already have found that they often can extend their growing season and increase their profits by growing inside plastic hoops or tunnels. Page, a Montrose-based Colorado State University small-acreage management agent, has been able to reduce expenses by building a tunnel on rails so it can slide from one location to another and handle a larger selection of crops.

The bows or trusses that usually would be anchored in the ground, he mounts on runners that slide up and down rails made from plastic decking limber.

Page’s movable tunnel measures 24 by 36 feet. He estimates that it cost $700 more to build than a permanent structure, but it was a money saver in the long run.

The structure would cost $4.50 per square foot if it were used only over one plot, Page says. But since it can be used on four or five plots, the cost per square foot comes down to about $1.25

“It’s a way of extending your money,” he says. “It really works out to be quite a bit cheaper.”

Page moves the tunnel to cover plots of winter greens, asparagus, tomatoes, peppers and basil. He plans to see how long into the fall he can grow raspberries in a tunnel, and will test a couple of different varieties to see which performs best.

The project was financed by a Western Sustainable Agriculture Research and Education grant of $11,230.



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