UNH strawberry research

Growing strawberries in low tunnels increased marketable yield by about 10% in both years of a study.

DURHAM — Researchers at the University of New Hampshire have more than doubled the annual yield of strawberries and quadrupled the length of the New Hampshire harvest season by growing day-neutral varieties in low tunnel protective structures.

According to a UNH news release, the new research out of the NH Agricultural Experiment Station provides a road map for growers seeking to increase production during what is normally considered the off-season for locally grown strawberries.

“Our study shows that local strawberries can be grown from early summer through late fall in our area. This is yet another illustration of the diversity of crops that can be grown in this part of the country during months that were previously considered the off-season,” said Kaitlyn Orde, a research associate who worked with Becky Sideman, professor of sustainable agriculture and food systems and UNH Cooperative Extension specialist in sustainable horticultural production.

Researchers evaluated eight varieties of day-neutral strawberries that produced fruit from early July into November in both years of the study. Traditionally, New Hampshire’s strawberry season is only four to six weeks in June and July.

Depending on the variety, annual total yields ranged from 7,600 pounds per acre to greater than 14,000 pounds per acre during the research.

“Given that New England growers recently have reported average annual yields of 5,900 pounds per acre to the USDA, these are quite competitive yields for our region,” Orde said.

The results were obtained using a relatively low planting density; the authors estimate yields could be increased if plants were grown at slightly higher planting densities.

Most New England strawberry growers plant June-bearing strawberries, which are strongly affected by day length and only initiate flower buds under short-day conditions, resulting in a brief period of fruit production each year.

“While June-bearing varieties are very productive over a short harvest season, they inherently limit availability of regionally produced strawberries during the remainder of the year, so instead, we import strawberries from elsewhere,” Orde said.

Researchers also grew the strawberries under low tunnels, according to the news release. They found that the low tunnels increased the marketable yield by about 10% in both years of the study and increased marketable yields during the last six weeks of the 2018 season, from mid-September to late October.

During this six-week period in 2018, plants growing under low tunnels produced 850 pounds per acre more than plants growing on open beds (no low tunnels), which is estimated at about $3,800 in additional revenue, the study found. Researchers also noted that plants grown under low tunnels required less labor for culling and the removal of runners.

This study was supported by the NH Agricultural Experiment Station, the UNH Cooperative Extension, the New Hampshire Vegetable & Berry Growers’ Association, the state of New Hampshire, the National Institute of Food and Agriculture and the U.S. Department of Agriculture.

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