Winter plantings with Aquaponics What is a salad? The most common salads are combinations of lettuce, carrots, and radishes, along with cubes of cheese and meat morsels, topped off by sprinkles of bacon and other shakers. This time of year, most of the greens are found in the aisles of grocery stores, coming from places other than your backyard. Imagine sitting in a classroom and having the question, “What is needed to grow the plants in your salad?” proposed. Most answer with sunlight, water, and dirt. Or ‘Soil’ would be the better answer. In the horticultural world there is a saying that Dirt is what you sweep off the floor. Soil is what you grow things in.
Salad created on February 13th with produce grown in the
If that is true, then the definition of soil is defined as a natural body comprised of solids (minerals and organic matter), liquid, and gases that occurs on the land surface, occupies space, and is characterized by one or both of the following: horizons, or layers, that are distinguishable from the initial material as a result of additions, losses, transfers, and transformations of energy and matter or the ability to support rooted plants in a natural environment. What would the best conditions be to demonstrate the needs of plants in the classroom? Can it be done simply with used milk cartons, potting soil, and marigold seeds? While that may be the simplest and most commonly used method in most classrooms, there is something unique happening in the Agriculture Education classroom. Something that can be dubbed CSI science, Can See It Science. There, the question of what plants need are being answered in the middle of winter, inside concrete walls, with rocks. Most people look into the growing barrels and ask “How is it possible that plants are growing out of the rocks?”. No garden soil here, just barrels of rocks, connected by hoses, with water cycling through it. While it might not be that simple, there is a lot CSI science happening with this project. The students involved, in the freshman Ag Science class at Chateaugay Central School, are watching it unfold. Spurred on by you tube postings and the trials of past aquaculture projects, the inquisitiveness of students and faculty, are bringing this unique system of plant production to life. For those not familiar with aquaponics, it is the cultivation of fish and plants together in a constructed, re-circulating ecosystem using natural bacterial cycles to convert fish wastes to plant nutrients. A balanced aquaponic system is mechanically simpler, but more biologically complex than either of its
parent technologies – re-circulating aquaculture or hydroponics. Together, each technology solves problems with the other, making it more thermodynamically efficient than either alone. The system constructed in the classroom originates from the CHOP System of Aquaponics as presented by “aquaponics guru” Murry Hallum of Australia. As I am writing this, it truly is amazing to think of the international origins of such a project in our school. CHOP is an acronym for Constant Height/One Pump. The system is a variation on the single pump system used by the UVI Aquaponics Research Centre. Where the UVI model employs the raft growing system, this CHOP system is adapted for use with grow beds. In a CHOP system, the water flows from the fish tank to the media-based grow beds, #2 stone in our case, before draining into a sump tank. A single pump in the sump tank then pumps the water back into the fish tank. Importantly, the level in the fish tank remains constant because the only water that leaves the fish tank is that displaced by water being pumped up from the sump tank. If a serious leak outside of the fish tank develops, the pump in the sump tank will eventually stop (because there is no more water flowing back into the sump tank) the fish tank will remain full. This eliminates a prospective point of failure. The advantages of the CHOP system include:
Flexibility in placement of the grow beds. Only one pump required – energy savings. No need for timers or float switches. No pump in the fish tank – avoids churning solids up. You can network two or more fish tanks so that nutrient levels remain constant right across the system. You can use a single mechanical and biological filtration system to serve several fish tanks. Water level in the fish tank remains at a constant level. Water tank remains full in the event of plumbing or equipment failure.
The disadvantages include:
More expensive to set up than a basic flood and drain unit. Requirement for a larger sump tank – equal to the total volume of water able to be simultaneously contained in the grow beds.
The two systems we have at school right now are the creation of students with faculty assistance. They consist of 55 gallon plastic barrels acquired from a gentleman in Rouses
Point after running an advertisement in the Free Trader, old garden hoses cut into pieces, cinder blocks from construction debris and 3x4 oak planks from the old gym. For each system there is a $20 submersible pump, $6 in shut off valves and $10 in plumbing parts for the bell siphons. Students marked and cut apart the barrels, assembled and tested the siphons in the grow beds, developed a layout for the system, and dumped in the rock growing media donated by the Malone Quarry. Ideally the system would be running with fish in the tanks supplying nutrients to the plants, however because of water temperature concerns for available fish, which is too warm for trout and too cold for tilapia, they have not been added yet. The systems however have been going through an “inoculation� process in which fish food has been added to start bacterial growth in the grow beds to aid in water filtration. Radish seeds were thrown into the growing beds to see how effective the systems would be. A few previously started lettuce plants were transplanted and took off beautifully. The growth you see in the pictures is about 3 weeks old. This project has combined construction skills, problem solving, media interpretation, and research based practices while also teaching the skill of adjusting to trial and error results. Students have learned that all plants need in order to grow is some form of light, water, nutrients and root support. We also had to adjust water flows to get the bell siphons to function properly and lamp height so as not to burn the plants We are amazed at the results thus far. Our next step includes placing some black plastic water lines next to the grow lamp to act as a solar heater. If this adjustment raises our water temperature from 74 degrees to 84 degrees, then the addition of tilapia is not far off.
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