low cost high tunnel construction

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9/17/13 Low Cost High Tunnel Construction - eXtension

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Low Cost High Tunnel ConstructionLast Updated: March 10, 201 0

Welcome

eXtension is an interactive learning env ironment delivering the best, most researc hed knowledge from the

smartest land-grant university minds acro ss America.

Find a U.S. Institutio n (http://www.extension.org/pages/18356/low-cost-high-tunnel-construction#)

Tim Coolong, University of Kentucky

Introduction

High tunnels (http://www.extension.org/pages/18358/introduction-to-high-tunnels) are becoming increasingly

popular for use by small farms who often market directly to consumers. Although they have proven to be

economically advantageous to farmers who wish to capitalize on high prices obtained either early or late in the

growing season, permanent high tunnel structures do represent a significant capital investment. The cost for a

standard size tunnel, including plastic (two layers) and all the materials required for construction can range

from $1.50-$2.50 per square foot without labor and freight charges. This represents an initial investment of

several thousand dollars, which is simply too much for some small farms. Although most growers are able to

pay for their tunnels within a few growing seasons, others cannot justify the investment. For this reason,

extension and research personnel at the University of Kentucky have been working on developing a low cost

high tunnel covered with a single layer of plastic that can be assembled or moved in an afternoon.

This low cost high tunnel only provides about 3 oF in frost protection, compared to 7 oF for a double poly

tunnel. This tunnel design has proven to withstand 60 mph winds with little damage in central and western KY

This tunnel will not withstand much more than a very light snow event (


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tunnel. This design is constantly being modified to find the most economical use of money and labor while still

providing a sturdy useful structure. Below is a detailed outline on how to construct this tunnel.

Constructing the high tunnel

In this tunnel we have already laid plastic in the field and transplanted. By assembling the tunnel over the

already formed beds we can use traditional tractor mounted bedshapers and transplanters, saving the need for

specialized equipment. Here anchors are made from one inch diameter pieces of steel pipe 18 inches in length

with a single turn of auger flight welded to the end. Photo credit: Tim Coolong, University of Kentucky

These anchors are placed on eight foot centers the entire length of the tunnel. Generally they are spaced 12 fe

apart, which is enough to easily cover two beds made on six foot centers. Photo credit: Tim Coolong,University of Kentucky


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The anchors are then augured into the ground with a small hydraulic driven motor which can be hooked to a

tractor. Anchors are driven into the ground so that the "hook" that is welded on the side is just at the soil level

Photo credit: Tim Coolong, University of Kentucky

Then 1.5 inch schedule 40 pvc pipe is placed over the anchors. Ty pically pipe can be purchased in 20 foot

lengths. A 20 foot pipe will form a tunnel 12 feet wide at the based with a center height of just over six feet.

Pipes should be painted with a latex paint. Experience has shown that non-painted pipe may cause plastic todegrade where it comes in contact with the pipe. Photo credit: Tim Coolong, University of Kentucky

Endwalls were constructed the previous season. These are made from 2x4 lumber and have a number of

aluminum channels attached to them for fastening plastic. They are quickly put in place and attached to the

end loops. In addition, ropes are run from either side of the door to anchors that are sunk deep into the groun

Mobile home anchors are inexpensive and work well for this purpose. Photo credit: Tim Coolong, University

of Kentucky


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A lightweight metal pipe is then attached to each bow using aluminum cross connectors. A typical source of pip

would be the top rail for a chain link fence. This pipe is very important as it gives the entire tunnel rigidity.

Demonstration plots showed that tunnels with the center pipe withstood very strong (60 mph) wind gusts whil

those without the pipe did not. The rigid pipe also helps shed water after rains. Photo credit: Tim Coolong,

University of Kentucky

Ropes are then attached to anchors at each end and attached to the first three bows on either end in crisscrossfashion. These ropes help tighten the tunnel and improve end-wall stability. Photo credit: Tim Coolong,

University of Kentucky


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Plastic is then unrolled and pulled over the house. Because the plastic is meant to be removed during the winte

months, a lighter weight (4 millimeter) plastic can be used if desired. However, 6 millimeter plastic has shown

to be able to withstand wind to a much greater extent than 4 millimeter in central KY. Once pulled over the

hoops, the ends of the plastic are attached to the endwalls using "wiggle wire" put into the pre-fastened channe

(shown in the far right photo).Photo credit: Tim Coolong, University of Kentucky

Then nylon rope is fed back and forth over the plastic attaching to the hooks that were welded on the side of th

anchors. The rope is sent down the tunnel and attached to every other hook then it is brought back up the

tunnel and attached to the remaining hooks. The rope is twisted at each hook so that the rope can be easily

tightened as needed. By using the rope to hold the plastic cover down, one does not have to permanently affix

the plastic to any base. Therefore when warm weather strikes the plastic can be pulled up on each side easily

venting the crop inside. In fact, this type of structure was used to grow organic colored bell peppers during the


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summer in Lexington, KY. It served to keep rain off of the peppers, reducing fruit rot and the spread of

bacterial spot of pepper. Photo credit: Tim Coolong, University of Kentucky

Total assembly time for a 160 foot long tunnel from start to finish can be done with 2-3 people in about 3-6

hours, depending on experience level. The end walls would take an individual about 2 hours each to build.

While these tunnels only give about 2-3 oF of frost protection alone-more if an additional layer of plastic or

remay is placed in the tunnel, they effectively increase the number of hours above 50

o

F when used in spring.Thus they promote rapid growth and early fruit when used for tomatoes. Above is a picture taken on June 20,

2008, in the mountain region of East KY. T he plastic had been removed, but one can easily see the difference i

growth and fruit set on the tomatoes 'Mt. Crest' planted in the tunnel and those outside the tunnel. Both were

planted on the same day in late April 2008. While not for everyone, these inexpensive tunnels can give growe

a jump on the season without a large investment of capital. Photo credit: Tim Coolong, University of Kentuck

This is an eOrganic article and was reviewed for compliance with National Organic Program regulations by

members of the eOrganic community. Always check with your organic certification agency before adopting

new practices or using new materials. For more information, refer to eOrganic's articles on organic

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