Extending the Season and Increasing Quality of Produce with Low Tunnels Year-rounding

The North Central SARE Farmer/Rancher Grants will be announcing its call for proposals towards the end of this month.  With that in mind, I am going to run a series of past awarded grant projects so you can read about the types of proposals that have been funded in the past and the results from their projects.  If you're interested in learning more about the SARE Farmer/Rancher Grants, I will host a webinar on Monday, Sept 10th from 7-8:30 pm.  More about this later.  In the meantime, I hope you learn much from this series of posts.  (debi)

Project Number:  FNC10-811 - Springfield, MO – Curtis Millsap

Objective: To explore using low tunnels as an economical way to extend the growing season.

Results: Locally produced food is growing in popularity as consumers’ interest in knowing where and under what conditions their food is grown is increasing. In the Midwest, though, most producers stop growing after the first frost and don’t have produce for up to six months a year. Also, there’s a two to three month period in the summer when it’s too hot to produce lettuce. High tunnels or heated greenhouses are too expensive, so we are exploring the potential of low tunnels to extend the growing season.

Galvanized electrical conduit bent
into half circles form the frames
for the low tunnels.

Millsap Farms is a 20-acre diversified farm near Springfield, MO. We raise 5 acres of vegetables, bedding plants and vegetable starts, along with some livestock. We sell our produce through farmers’ markets, grocery stores, our farm stand and the local community supported agriculture program.

We are exploring the potential of temporary low hoops with light coverings, sometimes referred to as quick hoops, as a way to extend the growing season, meet consumers’ desire for local food year-round and increase producers’ profits. The hoops are bent out of 10-foot galvanized electrical conduit into 6-foot diameter half circles, stuck into the ground 6 to 12 inches on each side and then covered with either a floating row cover or plastic.

Low hoops covered with lightweight
row cover provide a low cost, low risk
method of season extension.  In winter,
they protect crops from frost; in summer
they protect crops from intense heat.

We initially installed about 1,600 linear feet of hoops, covering a 6-foot wide bed of vegetables, for about $1,000 materials and $300 in labor. This covered 9,600 square feet of growing space for less than 15 cents per square foot. At the end of November, after several frosts in the upper teens, we were harvesting bok choy, beets, carrots, arugula, lettuce, spinach, green onions, kale, mizuna, and two types of turnips.

The potential of this approach appears tremendous, but further experiments are needed. There is only minimal information on the best way to build, maintain and cover these temporary structures. Among the details needing further research is the best kind of row cover, one that lets in enough light during the darkest time of the year but doesn’t promote overheating on occasional warm, sunny winter days. We will be expanding our research to additional beds, and testing different types of row covers to answer these and other questions.  Learn more at Curtis' blog.