Progress report for FNC22-1323
Project Information
Our farm occupies 40 acres, with 2.5 in organic (not certified) and regenerative vegetable production. It's a family operation involving myself, my wife, and all 8 of our children. We have been at it since October 2014. We practice cover cropping, manure and compost fertilization, and animal rotations in order to continue to heal our land from decades of conventional agriculture.
A huge part of our workload is starting and caring for seedlings for eventual transplant into the gardens. We have previously worked in a small lean-to greenhouse. It doesn’t have good thermal regulation, leaks, and requires a lot of fuel. Watering is a manual process, requiring constant attention. We periodically lose seedlings due to missed watering or flooding.
I’m building a new seedling greenhouse that is a 30' x 60' walipini style, dug 5' below grade, and covered with double layered plastic. To solve the above problems in the new greenhouse, I’m designing an integrated aquaponic seed starting and heating system with the following features:
- Use of a "rocket stove" mass heater to efficiently heat the greenhouse through use of thermal mass. This will release heat into the greenhouse over time for more even temperatures with less babysitting and fuel.
- A low profile fish tank to absorb heat from the rocket stove and circulate warm fertilized water through elevated "thin film" watering beds. Seedling trays sit in these beds, where the seedlings are consistently bottom watered through capillary action. This reduces or eliminates manual watering, reducing labor.
- As fish population increases, they can be sold for additional revenue.
The focus of research will be to evaluate feasibility of this system and effectiveness in meeting the following criteria:
- Improve thermal stability of the greenhouse.
- Provide more consistent soil moisture for the seedlings through use of thin film watering beds.
- Provide fertility for the seedlings and cleaner water for the fish, reducing stress and improving outcomes.
- Provide another revenue stream for the farm through fish and live plant sales.
- Reduce daily workload in establishing and caring for seedlings.
Outreach will be accomplished through social media postings and field days in conjunction with our local extension office's "Growing Growers" program.
Research
This project suffered multiple setbacks:
- 2022 was one of those years where nothing went right. I've been able to accomplish purchasing materials, though challenges surfaced. The construction of the Walipini style seedling house this project was to be conducted in was set back due to a retaining wall collapse last winter. I was excavating to level the floor in preparation for setting posts for the project and bringing rock in, and inadvertently dug a little too deep alongside one retaining wall. That night we had an unexpected heavy rainstorm that washed out the sand base from under the wall. With the base compromised, the saturation of the berm soil caused it to tip in and collapse. By the time it dried out, I was dealing with other breakdowns, repairs, and general spring farm activities. The whole year set a record for problems, and I am still constructing the greenhouse. My hope is to have the seedling house done this spring, and to conduct the project as planned, but essentially a year behind schedule. The biggest lesson of the past year's attempts to work this project has been a solid reinforcement of the old adage, "The best laid plans of mice and men often go awry."
- 2023 has continued the challenges of 2022. The main structure of the greenhouse was completed, and the tank, growing beds, and rocket stove were begun. However, due to extenuating circumstances, construction was not completed.
- Construction proceeded after that, but the entire construction project had been during a four year drought. We have high shrink-swell heavy clay soil, so when we finally got a whole lot of rain, the clay started swelling and shifting and pushing retaining walls out. In general, it made a mess of things. On top of that, the high tunnel shifted and is in the process of collapsing.
No results. See lessons learned to inform future projects on this topic.
Educational & Outreach Activities
Participation Summary:
Education and outreach was cancelled due to construction failures.
Learning Outcomes
- If you're going to do a dugout walapini style, make sure to invest in a proper, fully-reinforced poured concrete perimeter that's buttressed and reinforced and going to hold up over a long period (at least for heavy clay soils). We did concrete blocks mortared together. We did some buttressing (going back into the berm with cross-placed concrete blocks).
- The cost of a poured concrete perimeter would have been a show stopper for us (estimated cost $30,000).
- I think that if we hadn't done the dugout, if we'd just done a regular greenhouse frame but added the rocket stove and fish, it would have been accomplished fairly easily.
- Another tip would be to have drain tile buried to be able to pass air through with a fan, to help with mediating the climate in the tunnel. (As I work to rescue this structure and refill everything that's down in the pit, I'm going to add a bunch of drain tile (black corrugated plastic drain pipe) -- I'll zigzag it on top of the dug-down floor and fill in with sand before finishing with clay. Where the drain tile exits the ground at the other end of the greenhouse, the pipes will cluster together. I'll set up a fan to push air into the ground through that cluster of pipe. The other end is just open into the high tunnel (at the opposite corner). So in summer, the fan will take the hot air from the high tunnel and push it into the ground, and then the cool air from the ground will cool the greenhouse (or visa versa in winter).
Project Outcomes
See lessons learned.