High Tunnels

What are high tunnels?

High tunnels are unheated greenhouses that can help commercial farmers extend their growing season so that they can improve the profitability and productivity of their farms.

High tunnels are also an integral part of local food production systems in many parts of the United States. They aid fruit and vegetable crop production by extending the cropping season, providing protection from the elements (wind, storms, heat, etc.), and result in a more-stable production system that poses less risk of crop failure (hightunnels.org).

For more information about high tunnel construction, use, and Jacobsen lab research at UK, please watch these videos or continue reading. 

 

Where is the UK High Tunnel Research Facility located?

The UK High Tunnel Research Facility is located on the University of Kentucky Horticulture Research Farm in southern Lexington, Kentucky off of Man O' War Boulevard. 

 

What are the types high tunnels and things you should consider when constructing one?

High tunnels offer growers an innovative way reduce risks, increase yields, and protection from extreme weather conditions in Kentucky. However, high tunnels are no "silver" bullet solution and require significant financial investment, can be labor intensive to manage, and may be damaged or destroyed by extreme weather such as high winds, heavy snow, or hail (hightunnels.org).  This is why it is imperative to choose a high tunnel kit that best fits your production needs while still within your budget.  The most important step when constructing your tunnel is to read and understand the instructions that come with the kit your are building.  All designs implemented at the UK High Tunnel Research Farm are heavily based on manufacturer's instructions. The following are some considerations to make before selecting a high tunnel of your own (information from Dr. Shubin Saha's Presentation, "Structures and Site Selection," from the 2014 KFVGA Conference): 

 

Gothic style free standing single tunnel

Gothic style free standing single tunnel

Structure Types

  • Free standing single tunnel

    • Quonset

    • Gothic

  • Gutter connected multiple tunnels

Types of Covering Materials

  • Rigid or flexible

  • Variables: cost, durability, longevity, light transmittance, heat retention

 

Selection Considerations

  • Location- Is there an established market for a high tunnel in your area?

  • Strength and design

  • Working conditions

  • Initial investment cost

  • Labor availability

Orientation

  • Maximize light intensity and uniformity

  • N-S orientation to maximize light uniformity

  • E-W orientation to maximize total light

What types of high tunnels can you find at the UK High Tunnel Research Farm?

The facility includes three stationary and three moveable high tunnels, all built in 2011 and are laid out in an East-West orientation. The Jacobsen Lab manages the tunnels growing a mix of fruit, vegetables, and cut flowers year round. Moveable tunnels are high tunnel structures that can be pushed or dragged from one area of a field to another.  All of the high tunnels are gothic style with each measuring 30' x 72'.  This structure contains the maximum square footage allowed for in the National Resource Conservation Service (NRCS) Seasonal High Tunnel Initiative.  This is the environment quality incentive program (EQIP) which provides financial and technical assistance to agricultural producers to plan and implement conservation practices. 

Our structures are covered in two layers of 6ml 4 year plastic. The plastic on top of our tunnels are double layered with an inflation fan filling the space between layers with air. The fan's electricity is the only energy that these tunnels directly use.  The doors and endwalls do not come with a standard kit.  We have 8'x8' sliding doors covered in polycarbonate sheeting. The doors slide on standard barn or livestock door hardware.  The tracks are available from agricultural supply companies.  These endwalls are framed in with 2x4's and instead of using furring strips to keep the plastic tight we have reused old drip tape.  All other plastic is attached using wiggle wire.  

Why do we use moveable tunnels at the UK High Tunnel Research Farm?

Throughout the season one can move the high tunnel structure from one plot to the next which allows for greater flexibility in crop rotation, as well as more opportunity to incorporate cover cropping into our system.  Another reason we are experimenting with moveable tunnels is to avoid disease and insect pressure as well as prevent soil salinity accumulation from heavily used soil amendments.  In our moveable tunnel system, no area is covered by our tunnel for more than 9 months out of the year. 

The moveable high tunnel structures are rotated between three adjacent plots.  In the past, we have moved the tunnels two times a year, but we are currently only moving them once per calendar year.  By staggering the position of the tunnels, we avoid shading problems.  

Each of our moveable tunnels is slightly different and the ways that we move them are different as well.  Generally speaking, two out of the three tunnels move by dragging across the ground by skids.  The other remaining tunnel moves on casters on round galvanized pipe rails.  More information on how these are constructed and moved can be found at http://ukhtrf.webs.com/. 

What crops do we grow, how do we grow them, and why?

Our operation features a diversified year round vegetable rotation. We combine traditional crops, like tomatoes, with other profitable crops such as greens, root vegetables, and beans.  This means we can harvest continually year round while still practicing crop rotation.  Our tunnels are always in production with multiple different crops and varieties. 

We grow in eight 30 inch beds running the length of the tunnel with about 2 feet of space at the end of each tunnel.  The beds are set 42 inches on center.  This gives us about 12 inches of aisle space between the beds.  This can be a tight working area, but this arrangement allows us to use the space completely. 

In the course of a given year we will grow a salad mix, head lettuce, spinach, carrots, beets, strawberries, cucumbers, bush beans, and several varieties of kale, peppers, eggplant, and tomatoes.  Once we have selected our variety of plants, we need to think about soil moisture and fertility.  One of the advantages to farming in tunnels is a disadvantage: rainfall never reaches the crops.  Irrigation water will be the only moisture that the plants receive.  Each tunnel has a black plastic orchard tube header line that supplies standard drip tape or T tape. This header delivers the moisture directly to the roots of the plants while avoiding leaf wetness which can contribute to foliar disease and fruit rot in the field.  All of the supplies for this irrigation system are available from horticulture supply companies. 

Since building our tunnels, the set up discussed previously has not changed but we have transitioned from 2 inch blue flat lay supply lines to frost free hydrants.  This way each tunnel is watered individually.  These hydrants feed directly into the black header system.  We use an integrated nutrient management plan incorporating compost, pelletilized poultry manure, and with some crops, fertigation with fish emulsion.  The compost is used primarily as a soil amendment but we account for the nitrogen and the phosphorous in the compost when calculating our other fertilizer amendment rates.  For specific fertility application, consult extension materials about your crop. 

Most of our tillage is done with a BCS 853 walk behind tractor.  We also use a mower, regular plow, and chisel plow regularly in our tunnels.  We also rely heavily on hand tools in our production system. 

What research is conducted in the high tunnels?

Our facility focuses on economically profitable, year round diversified crop production by incorporating agroecological practices into Kentucky high tunnel systems. This includes the integration of both traditional high-value crops (i.e. tomatoes) and other highly marketable local produce (i.e. leafy greens, legumes, etc.). The facility is coming to the end of its preliminary establishment, and we are excited to proceed with the important research so many high tunnel growers want.