High tunnels mitigate nature's effects on crops

It’s a season of change for Missouri farmers as interest in the use of high tunnels – or “hoophouses” – grows.

These unheated tunnels, basically greenhouses that resemble Quonset huts, provide protection from weather damage and can extend regional growing seasons.

A high tunnel under construction on Missouri State University’s Mountain Grove campus is designed to give educators and growers an up-close view of how hoophouses can be used in the field.

Marilyn Odneal, a horticulturist at the William H. Darr School of Agriculture at MSU-Mountain Grove, is using about $6,000 of a $20,700 grant from the U.S. Department of Agriculture’s Rural Business Enterprise program for the construction of a high tunnel that is 30 feet wide by 96 feet long. Peonies, strawberries and tomatoes will be planted in the high tunnel and outside so horticulturists can observe and compare the difference in development, flowering and growth.

The plastic-covered high tunnels result in a warmer environment during late fall, winter and early spring seasons, giving growers the advantage of starting crops earlier in the spring and pushing harvest until later in the fall. Without the tunnels, winter production isn’t impossible, but it is restricted to the availability of supplemental heat, according to www.hightunnels.org. The Web site is part of a U.S. Department of Agriculture-sponsored project for testing and promoting high tunnel systems in the Central Great Plains.

“I’ve been very interested in high tunnels as there has been research conducted on extending the growing season in this area, and there’s no other demonstration high tunnels around,” Odneal said.

Besides keeping crops safe from weather elements – including protecting plants with longer stems from wind damage – and extending the growing season, high tunnels also can offer a layer of protection from fungal diseases.

“Some cool-weather crops such as lettuce can be grown for a longer period of time,” she added.

New twist on an old idea
The Mountain Grove growing area is considered part of Missouri’s south-central region, but the growing techniques Odneal will be demonstrating will be applicable in other regions, said Patrick Byers, southwest region horticultural specialist for the University of Missouri Extension Office in Springfield.

“Farmers have been growing in protective structures for centuries, but high tunnels as they have evolved today with moveable sides and plastic skins are a relatively new technology for Missouri,” Byers said.

Modern high tunnels have ventilated sidewalls that can be raised in warm weather and lowered on colder, usually crop-destroying nights.

However, moving those walls can be labor-intensive, which can be a negative aspect of high tunnels for some, said Andy Read, a University of Missouri Extension horticulture specialist for the south-central region.

But he said there are ways to address the issue.

“Some farmers have even gone with automated sidewalls with timers,” Read added.

A high tunnel’s plastic cover also has to be removed on some models during winter to keep them from collapsing under the weight of snow.

Depending on the sturdiness of the high tunnel, some, including the Mountain Grove demonstration tunnel, that is slated for completion in August, have permanent plastic covers that do not need to be removed.

Read said the average cost of a high tunnel ranges from $1.50 to $3 per square foot, depending on factors such as the model, the amount of ground preparation needed and whether row covers or other options such as automated timers will be used. Read said the cost depends on what type of ground preparation has to be done, the type of structure and other costs such as row covers.

Tunnel economics
Using high tunnels to extend productive seasons can help growers boost their bottom lines, too.

“When looking at the economics, vegetable growers who grow tomatoes have found the highest return for the early season prices,” Byers said.

Read said that in late July when most of the tomato growers have their product at market, they can expect to earn a wholesale price of as little as 75 cents to $1 per pound, while early growers harvesting with high tunnels can command up to $3 a pound by having their product on the wholesale market three to four weeks earlier.

Byers estimated that the average profit is $1 per square foot for tomato growers using high tunnels.

He said the profit-per-square-foot estimate for traditional field growing varies depending on the crop and the grower’s use of spacing.

According to 2007 data – the latest available from the U.S. Department of Agriculture’s Missouri Agricultural Statistics Service – $7.5 billion of agricultural products are sold in Missouri each year, and $3.5 billion of that comes from crops, including those from nurseries and greenhouses.

Read said it’s unknown how many growers are incorporating high tunnels into their operations and it’s too soon to forecast the impact high tunnels will have on agriculture statewide.

The Natural Resource Conservation Service, a division of the USDA, is offering growers in 38 states cost-sharing grants to install high tunnels for a pilot study aimed at promoting organic farming.

According to www.hightunnel.org, the pilot project is funded through the Environmental Quality Incentives Program, the EQIP Organic Initiative and the Agricultural Management Assistance Program.

Area growers interested in learning more about the program can contact the USDA’s Springfield Service Center, (417) 831-5246.

Byers is optimistic about the growth potential for high tunnel use.

“I see a great future for tunnels, and because of it, I see a great future for local vegetable and fruit production,” he said.[[In-content Ad]]