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10 Reasons NOT To Grow Tomatoes In High Tunnels

Tax law changes and protected growing environments can impact high tunnel bottom lines.

John Vogel, Editor, American Agriculturist

February 5, 2014

3 Min Read

Yes, you read the headline correctly. The plain, unvarnished agricultural truth is that making money with high-tunneled tomatoes isn't a no-brainer, confess Steve Bogash and Judson Reid, Penn State Extension horticulturist and vegetable specialist, respectively.

Every good reason to grow tomatoes and other high return vegetables and small fruits in high tunnels has a compelling argument against it, they contend. So consider these seldom-mentioned negatives before succumbing to the rush to high-tunnel every farm.

Return on investment: Poorly managed tunnels yield equal or less than field plantings and the amortized costs of the structure, plastic film and specialized equipment are substantially higher. And, if the Section 179 accelerated depreciation deduction limit has been cut to $25,000 for 2014 – down from $500,000, it must be weighed against its ROI.

Increased risk: Metal tube structures do fail, as do plastic covers.

Higher pest pressure: While tunnel cultures bring opportunity for higher crop quality, aphids, whiteflies, thrips, spider mites and broad mites also thrive under tunnel conditions. Every crop reacts differently under tunnel conditions versus field grown.

Irrigation management intensified: This is especially so on the margins of the season with less sunshine. Growers must adapt to rapidly changing conditions and know when to increase irrigation flow to maximize plant growth, reduce cracks, and blossom end rot.

Tunnels also require more irrigation than field plantings. Farms with less than adequate water supply should look at tunnels with caution.

Increased disease pressure: While tunnels do reduce early blight and Septoria leaf spot, other diseases are accentuated. Brown leaf mold, powdery mildew, and botrytis are standard fare under high tunnel conditions.

Tunnels perpetuate viruses: Viruses such as Tobacco Mosaic are spread mechanically as workers move the virus down the row with weekly suckering or pruning. High-tech greenhouses have disinfection protocols in place to reduce the spread. But soil-based systems are more difficult to disinfect than a concrete floor.

Sagging soil health and nutrition: Tomatoes are the single most popular high tunnel crop due to their high return and market demand. There's considerable pressure not to rotate tunnel crops as you would fields. That can steadily increase soil-borne diseases such as Fusariums and Verticilliums.

Since it never rains in a tunnel, all nutrients that the roots utilize are within the drip irrigation zone. This root area can quickly be exhausted of nutrients. Injected and foliarly-applied nutrients are necessary to maintain optimum nutrient levels.

Negative R values: Under early and late season short and cloudy days and clear, cold nights, it's possible to have lower temperatures last longer in a high tunnel than outdoors.

More management and labor: Pest populations and infestations tend to come on quicker under high tunnels than outdoors, requiring a very proactive management program. Not every manager has the time to accommodate the increased demands of constant canopy management, pruning and trellising chores.

Competing against subsidized tunnel purchases: Growers who purchase tunnels without grant subsidies may pay 40% to 60% more. Enough said.

So, Bogash and Reid conclude that there's a less glamorous side to high tunnels. While they're optimistic about the role of high tunnels on vegetable farms, they emphasize that the technology isn't ideal for all farms.

About the Author(s)

John Vogel

Editor, American Agriculturist

For more than 38 years, John Vogel has been a Farm Progress editor writing for farmers from the Dakota prairies to the Eastern shores. Since 1985, he's been the editor of American Agriculturist – successor of three other Northeast magazines.

Raised on a grain and beef farm, he double-majored in Animal Science and Ag Journalism at Iowa State. His passion for helping farmers and farm management skills led to his family farm's first 209-bushel corn yield average in 1989.

John's personal and professional missions are an integral part of American Agriculturist's mission: To anticipate and explore tomorrow's farming needs and encourage positive change to keep family, profit and pride in farming.

John co-founded Pennsylvania Farm Link, a non-profit dedicated to helping young farmers start farming. It was responsible for creating three innovative state-supported low-interest loan programs and two "Farms for the Future" conferences.

His publications have received countless awards, including the 2000 Folio "Gold Award" for editorial excellence, the 2001 and 2008 National Association of Ag Journalists' Mackiewicz Award, several American Agricultural Editors' "Oscars" plus many ag media awards from the New York State Agricultural Society.

Vogel is a three-time winner of the Northeast Farm Communicators' Farm Communicator of the Year award. He's a National 4-H Foundation Distinguished Alumni and an honorary member of Alpha Zeta, and board member of Christian Farmers Outreach.

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