High tunnels and your operation

High tunnels are becoming quite popular with many growers throughout the U.S. and are a proven technology for vegetable, fruit, strawberry and flower growers. These tunnels vary in size and are large enough to allow the use of irrigation systems, tillage equipment and even small tractors. Many growers use high tunnels for season extension, which can result in greater crop production from smaller acreage over a longer period of time.

Strawberry plants in a high tunnel.

High tunnel is a general term used for any greenhouse-like framed structure that modifies the “enclosed” environment to create more favorable growing conditions. High tunnels can be home-built or commercially constructed, but usually consist of a wood or metal frame covered with a single layer of 6-mil polyethylene plastic. The end walls can be detachable or framed-in for doors and ventilation, and side walls can be rolled up for ventilation. Modern high tunnels are found in many shapes and sizes, and are easily customized to meet the needs of the individual grower for a variety of crops that can be produced within the tunnels. In many agricultural areas, high tunnels have become so specialized and sophisticated that they are covered year-round, have heating and irrigation systems, and multiple vents in the ends and even in the roofs. Many of these high-tech tunnels have crop support systems that are built into the design and engineered to hold the weight of the crop. These tunnels can produce crops year-round in many areas, and are often moveable to allow for a rotation system.

Crops produced in high tunnels

The most common vegetable crop currently grown in high tunnels is tomatoes, using either stake or trellis support systems. Some tomato growers in New Jersey produce tomatoes on trellises in 200-foot-long tunnels specially constructed to support the crop weight of trellised tomatoes. These production systems yield tomatoes through November, compared with field tomatoes that are generally picked for four to six weeks in August and September. Although growers find that there is much more work and management involved with high tunnels, it pays off in significantly higher yields and higher fruit quality. Other vegetable crops grown in high tunnels in the mid-Atlantic region include leafy greens, lettuces, spinach, peppers, cucumbers, melons, herbs, onions, and even eggplant and beans.

There are many different high tunnel systems on the market. Most can be modified to meet your crop production needs.

Advantages of high tunnels

One of the most important advantages of high tunnels is that the growing season can be extended several weeks or more in both the spring and fall. A survey taken in the Midwest showed that, on average, high tunnels produced crops nine months of the year. These crops often bring premium prices when produced early in the season, before field production is ready, or late in the season, when field production has ended. Strawberry growers in New Jersey find that their production season is extended with a more uniform harvest that is spread out more evenly over the entire harvest season. Also, high tunnels generally offer greater environmental protection, especially increased frost and wind protection. Importantly, rainfall is excluded, and for strawberry growers this not only means that rain can’t interfere with picking, but also helps to reduce fruit rots. Because rainfall does not affect crops within high tunnels, damage from foliar diseases will be reduced. High tunnels also offer some insect protection, especially during the early season before the sides are rolled up. Water needs can be more precisely managed with sprinkler or drip irrigation systems, which can also be used for delivery of fertilizers, fungicides and insecticides.

This is a Dosatron unit in a high tunnel for application of nutrients, soil pesticides, etc., through the drip system

Disadvantages of high tunnels

Crop management increases significantly with high tunnels. This includes heat and humidity management, as well as water and fertility management. More mildews and leaf molds can occur in high tunnels if high relative humidity is left unchecked. Soilborne diseases can also build up rather quickly if left uncontrolled, or if proper crop rotations or tunnel relocations are not followed. Because no rainfall occurs within the tunnels, fertilizer salts tend to build up in the soil. Remember that space is limited within tunnels, and the cost per square foot of production is higher. For the operation of tractors and equipment within tunnels, a minimum of 6-foot sides is recommended.

There are many different high tunnel systems on the market. Most can be modified to meet your crop production needs, and often a company will work with you to accommodate your specific needs. Selection of a high tunnel depends on many factors, including local environmental conditions, crops and markets, as well as your budget. Almost all high tunnels give growers a quick rate of return on investment, and go hand-in-hand with roadside markets and longer production seasons. More information on the construction and use of high tunnels can often be found at your local county agricultural extension office.

Dr. Gerald M. Ghidiu is the vegetable entomologist, and Dr. Andy Wyenandt is the vegetable pathologist, stationed at the Rutgers Agricultural Research and Extension Center, Bridgeton, N.J.