Tool Dude's Blog: Johnny's Quick Hoops Hotbed Trial at White Gates Farm

On 12/6/10, we met with Hank Letarte, a farmer/entrepreneur in Tamworth, NH. A renaissance man of sorts, Hank has been an engineer, power plant operator, landscaper, cattle farmer, and now a biodiesel manufacturer. He teaches classes on animal processing and lead safety, among others. With the help of the NRCS , he recently added two Ledgewood high tunnels to his property. He now sells vegetables, beef, poultry, and pork at his farm and a local farmers' market. There's more info in this blog entry on Hank and White Gates Farm:

Farm Visit - White Gates Farm 3.30.11
He has a sand pit on his property and when the local tree service needed a place to dump wood chips, he decided to take them.

Noticing that they were composting and creating heat, he got an idea – why not harness that heat and use it to grow winter vegetables? He created a windrow 40 ft long by 8 ft wide on top. He then added six inches of loam on top. His thought was some type of hooped structure or tunnel on top to retain the heat. At that point, he enlisted our help. This is how it looked when we arrived.

This thermometer, inserted just beneath the loam, read out at about 60 degrees F. When fully inserted into the middle of the pile, it settled around 140 degrees F! We were both impressed and intrigued. I decided that the best structure for this would be six ft wide Quick Hoops low tunnels, because the wood chips could support them. We offered to help him with materials and as the conversation progressed, it was evident that he would need more than just materials, so we offered to help him set it up and plant. We went back to the farmhouse and laid out some rough plans.

Thinking that a certain size heap (or cross-sectional area in this case) would be needed in order for the chips to reach ‘critical mass’ for adequate composting, we asked him to create a second windrow, about half the height as the first, to see if it would generate the same heat. In other words, how deep do they need to be for this to work?

Threading the needle between winter storms, Adam and Andrew Mefferd went back on 12/9/10 to plant and set up. It never got above 12F in the pit that day. We knew the loam wouldn't have sufficient nutrients to sustain the trial, so we had a 2 yard sling bag of Compost Plus delivered from Vermont Compost. Unfortunately, the compost was frozen solid 3-4 inches in from the outside. So we had to hollow it out like a big pumpkin.

We spread a 2-3” layer of compost on top of the loam, which itself was also frozen solid and attempted to work it in with the Tilther. This worked in some spots and the Tilther just bounced around in others. So, for the most part, this was going to be just a heavy top-dressing.

After tilling and raking, we used the bed prep rake with tubes attached to the tines to mark three rows.

Then, we planted:

Tytan Parsley

Vit Mache

Mei Quing Pac Choi
Red Ace Beet

Elegance Brassica Mix

5-Star Lettuce Mix

Hakurei Turnips

Rover Radish

Bright Lights Swiss Chard

Along with the seeds we brought, Hank also had three trays of lettuce seedlings for us to plant.

Erecting the hoops. We drove t-bars in the ends as deeply as we could and used hand pegs to secure the Agribon and plastic.

Both windrows had mirrored plantings for easy comparison. Hank was also going to add sand along the sides to make the tunnels extra secure.

*********************************************************************

On January 20th, 2011, our QA manager, Bonita Nicolas and I stopped on our way to the NOFA NY Winter Conference, to check on the trial and install some temperature loggers.

There already were signs of life in the big tunnel.

*********************************************************************
On January 24th, we stopped in the pit at 9:00 at night and picked up the loggers.

*********************************************************************

On March 30th, I returned again to check on the trial.

Hank, removing the cover.

In the tunnel on the big windrow:

In the tunnel on the smaller windrow:

Summary and conclusion: There's really no new product as such that we were trying to develop here, just investigating the feasibility of a different method for season extension. The heaps definitely produced heat. The fact that anything was growing in January (after being planted in December) is pretty impressive in and of itself. However, the trial definitely had its challenges. The cover blew off several times, the thin layer of potting soil we added only had just so much nutrition to offer, the soil was quite dry when inspected in March having never been watered, and we were trying to grow vegetables during a period know as the 'dead zone' with very short day length. What I can conclude is that the heaps definitely produced heat, and the bigger one produced more than the shorter one. We saw anywhere from a 10 to 34 degree temperature differential between the inside and outside air. It also had better results than the shorter bed in the way of overall plant germination and growth, so the added heat promoted earlier growth. As for feasibility, I'm not quite sure. Hank plans to do more with hot beds, but that is just in the planning stages right now.