High tunnel interest continues to grow
High tunnels are beneficial for production of several annual crops in northern climates like Michigan.
Since they have been used commercially in the United States for 10 or more years, high tunnels can hardly be considered “new technology.” However, growers continue to be introduced to their benefits, which include greater and higher quality yield, season extension, disease reduction and others. The first crop many vegetable producers want to place in tunnels is fresh market tomatoes. However, they can be one of the most difficult crops to grow under tunnels.
Tunnel-grown tomatoes have larger plants, leaves and fruit, than the same cultivar grown out of the tunnel. Therefore, nitrogen levels need to be reduced at least 30% below field rates. Physiological problems such as gray wall, yellow shoulder and green core are also more prevalent on tomatoes grown in tunnels. Penn State Regional Horticulture Educator, Steve Bogash emphasizes the need for tissue testing and nutrient management, especially potassium, to obtain quality tomato fruit (http://glexpo.com/summaries/2010summaries/Tomato.pdf). Many of the fruit problems observed in fresh market tomatoes do not show up in the smaller-fruited cherry or grape tomato cultivars.
Vegetable crops that have performed well in high tunnels in Michigan include cucumbers, leafy greens and herbs. Testing still needs to be conducted on other vegetable crops.
Some flowers have also performed well including snap dragons, zinnias, sunflowers, statice, gomphrena and others. Dahlia and cosmos have not done well probably due to elevated summer temperatures in the tunnel. Cut flower stems are generally longer and colors appear brighter so they can obtain a premium price in the market place.
Michigan State University’s Dr. John Biernbaum has written a manual on hoop house production. The manual provides information producers need to make decisions when considering tunnels or growing crops using tunnels. Research results can also be found in several SWMREC Annual Reports at http://agbioresearch.msu.edu/swmrec/publications.html.
A main concern for high tunnel producers no matter what crop they grow is water management. Since the planting is covered with plastic, irrigation is a necessity. The only water the plants receive is what the grower gives them so close attention needs to be paid to irrigation scheduling. Some plantings will need watering twice a day or more depending on the production practices employed (flat, raised beds, containers, etc.).