Protecting Florida's $80 million blueberry crop from freeze damage is always a wintertime challenge, but a University of Florida study shows that structures called high tunnels could shield plants from cold and promote earlier fruit ripening.
Though the initial investment can run from $18,000 to $25,000 per acre plus labor, high tunnels deliver better-quality fruit, bigger early yields and higher prices if growers beat competitors to market, said Bielinski Santos, an associate professor with UF's Institute of Food and Agricultural Sciences.
The study, published in the current issue of HortTechnology, tracked two growing seasons on a commercial blueberry farm in Alachua County. The results showed that temperatures outside the tunnels plunged to freezing or near-freezing 61 times during the study. Temperatures fell that low just three times inside the unheated tunnels.
High tunnels may increase air and soil temperatures and protect the plants from wind and rain damage, leading to better flowering and more fruit, said Santos, based at UF's Gulf Coast Research and Education Center in Balm.
Plants grown in the tunnels produced about 4.5 tons of ripe fruit per acre by the end of March; no ripe fruit came from similar plants grown outdoors during that time. Wholesale prices for domestic blueberries are highest early in the season, starting at about $7 per pound in early April, he said.
"Usually, Florida growers start harvesting in early April," Santos said. "The more fruit you can harvest early in the season, the more money you'll make."
Growers can also save money with high tunnels because they minimize the need for another freeze protection strategy--sprinkling the plants with water to form a layer of ice. In the study, tunnel-grown plants needed about one-tenth the water for freeze protection as plants grown outdoors.
The study involved two blueberry varieties developed at UF, Snow Chaser and Springhigh. Snow Chaser is especially well-suited to life in high tunnels, Santos said.
Made by stretching thick plastic sheeting across an arched frame, high tunnels resemble Quonset huts, he said. Although they have variable dimensions, most tunnels have roofs anywhere from 8 to 20 feet high, with ends and sides that can be open or sealed, depending on the weather.
The technology is popular in other parts of the world, but still catching on in the United States, Santos said. In Florida, high tunnels and other protective structures account for about 250 acres of production, mostly for high-value crops such as blueberries, strawberries, tomatoes and bell peppers.
"We always thought it was really complicated and expensive," Santos said. "So for the past six years I've tried to 'vulgarize' the technology and develop a system anyone can use."
Santos said he knows of one Florida blueberry grower using high tunnels; the owners tried 2 acres in 2010 and later expanded to 80 acres. Others have expressed interest in the system.
Santos and co-author Teresa Salame-Donoso, a research associate at the Balm center, have begun collecting data for an economic study on blueberry production in high tunnels.
"We already have some numbers, and we're collecting the kind of information growers need to make up their own minds about using high tunnels," he said. "I see more people doing it eventually."