SARE — BOX TURTLE FARM

Box Turtle Farm and Millsap Farms Winter 2023 SARE Study

LB White Premier 170 ductless, portable heaters are 99% efficient and safe to use in an enclosed space with people and crops. Photo at Millsap Farms

Two lengths of convection tubing were attached to the heaters in house to distribute heat throughout the tunnel. Photo at Millsap Farm

All weather ducting was added to one discharge side of each heater in order to reach the far side of the tunnel. Photo at Millsap Farm

Our convection tubing utilized a single row of vent holes spaced 12 inches apart. Tubing can be ordered in any configuration. Photo at Millsap Farm

Convection tubing inflated with vents oriented to the left. Box Turtle Farm

Lesson learned. Orienting the convection tubing discharge vents to the side resulted in burned crops. Tubing was repositioned with the discharge vents to the top. Photo at Box Turtle Farm

Uninflated convection tubing in green curly kale. Inflation of the tubing was unhindered by the overstory of kale. In this instance the convection tube holes were oriented down to the ground so the kale would not be burned. Photo at Box Turtle Farm

We are a four-season farm, utilizing unheated high tunnels both for crop protection and season extension. During the winter months we utilize many layers of frost blankets to keep crops from freezing solid. This is a very time-intensive process and our activities, both farm and personal, are determined by the weather for any particular day. In addition, sometimes our best efforts are futile, especially when we see temperature fluctuations of 60 degrees in a single day in early winter. Our friends at Millsap Farms in Springfield, MO, operate the same way. High Tunnels are not designed to be greenhouses, and installation of greenhouse heaters would be both costly and inefficient. Together we set out to find a better way.

In 2023, we jointly received funding through USDA’s SARE program to study the efficacy of adding modular propane heaters to high tunnels to reduce the risk of crop loss due to fluctuating winter temperatures. Our project hoped to find a more sustainable (and less expensive) method of providing minimal heat (maintaining a minimum temperature of 35 degrees Fahrenheit).

Project Design

Each farm utilized two high tunnels. A highly efficient, non-venting propane heater was installed in each tunnel, with two convection tubes running the lengths. Two tunnels, one at each farm, also utilized a single layer of heavy frost blanket (Agrifabric Pro 50) over the convection tubing and crops to minimize heat loss and fuel usage. Fuel usage in each tunnel was compared.

Highlights

Use of frost blankets over the crops and convection tubing resulted in a fuel savings of 60-75% compared to the uncovered tunnel.
Warmer tunnel temperatures allowed the frost on both the poly covering the tunnels and the frost blankets to melt more quickly in early morning, allowing the farmer to remove the frost blankets earlier in the day, both of which increased the amount of sunlight available to crops.
Warmer tunnel temperatures also improved the farmers’ quality of life by allowing greater flexibility as to when row covers needed to be reapplied in the evening.

For more detailed information on project set-up, including products used and trials and tribulations encountered, please check our video https://youtu.be/W05AwkLz4xo.

Complete project details and updates can be located on the SARE website.

You can find more information about our friends at Millsap Farms, including info on their CSA and Pizza Night Club at Millsap Farms.

You can also find more information about our utilization of high tunnels in this video, which also features Curtis Millsap, produced by New Growth Community Development.

Box Turtle Farm and Millsap Farms Winter 2023 SARE Study

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