By Westley Lund, SIFT Intern
I am an agriculture intern for NCAT this summer and fall on the SIFT farm. I am currently getting my Masters in Environmental Engineering at Montana Tech, and I am working on a thesis project on reclamation work for a local stream in Butte that is contaminated with heavy metals. I was excited to have this opportunity to work with NCAT because of the wide range of knowledge and projects that I would have a chance to work on. One project I was most interested in was helping to repair and start operating a hydroponics system in one of our greenhouses.
A hydroponics system is a method of growing plants without soil, using nutrient solutions dissolved in the water. The nutrient material can come from a wide variety of sources, such as fish waste, manure, and synthetic nutrients. Our hydroponics system is set up to run synthetic nutrients, and I added a method of using compost tea as our secondary nutrient source later on.
The hydroponics system is pretty simple in design, using water pumps to circulate the nutrients through a system of 3â€ť PVC pipe with holes cut out to hold the water solution and plants, and to return the nutrients through tubing to recirculate them back into the system. Other parts of the system include holding tanks for the nutrients, air stones, and water heaters, which Iâ€™ll explain later.
After its original design, our hydroponics system had issues circulating the nutrients because there was no way to flush the material out of the PVC pipes that stored the plants. This ended up causing plants to die and the material to build up, settling on the inside bottom of the PVC. To fix this problem, we installed a PVC â€śTâ€ť joint, from which we could run tubing and a valve that could be opened to flush everything out of the PVC and back into the mixing tank. This fix worked with great success.
After we got the hydroponics system circulating nutrients more efficiently, we added some basil and lettuce plants to the hydroponics system running on synthetic nutrients. Some plants died off pretty quickly because of the fluctuating water levels in the PVC and because the roots werenâ€™t well-developed yet. Eventually the plants that survived the initial transplant took off and have really shown good growth.
One of NCATâ€™s goals is to have more sustainable and cost-effective methods for different things we do every day, like growing vegetables. So I thought of a way to supply nutrients from resources that we already have on the farm. We have many different compost piles at different stages of production that we add to our vegetables during planting to add extra nutrients to the soil. I have seen a method of making compost tea, in which water is dripped through compost material collected in a bucket. I thought this could be an effective way of supplying nutrients while also using local compost material we already had on site (itâ€™s really easy to make at home, too!).
For my design, I constructed a three-bucket design with holes in the bottom of the buckets. I then placed a rag over the holes in the buckets to keep the finer material from flowing to the next bucket and into the tea. The bottom bucket was filled with completed compost. The second bucket was filled with half manure and half fresh compost. The top bucket was filled with vegetable scraps and old potting soil. I placed another bucket under the three buckets of compost to catch the compost tea. I would run this water through the system two to three times until the water looked like really dark sweat tea, at which time it would be ready.
The compost tea has lots of nutrients in it, but there is no way for the plants to directly use it. Itâ€™s worth explaining the science behind this. After collecting the compost tea, the nutrients are in a form that canâ€™t be used by the plants but can feed lots of bacteria that are in the tea. After the bacteria consume these nutrients, they can be used by the plants. In order to remove the nutrients from the bacteria, they have to be eaten by a larger life form (protozoa, fungi, or other microscopic organism). After all these bacteria are eaten, the nutrients become free-flowing in the hydroponics system. So before we add the compost tea into our system, we bubble air through an air stone in the tea for 24 hours to selectively pick aerobic (oxygen-using) bacteria because anaerobic (without oxygen) bacteria can be harmful to the plants in the hydroponics system.
|PVC holders in the SIFT hydroponics system. Photo: NCAT|
We have been testing this new compost tea as a source of nutrients for our hydroponics system for a couple of weeks, and we placed a variety of plants at different stages of growth in the bottom the PVC holders shown in the photo. We have seen really good root growth over the course of this time, and the plants appear to be responding to the nutrients.
I have really enjoyed my time working with NCAT on the SIFT farm because I've had the chance to learn different ways to grow vegetables that I never considered before my time here. I hope this blog will encourage readers to consider hydroponic systems more often because, as an environmental engineer, I see the need to grow more food for the world in a more efficient (space-saving) and sustainable way.