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Growing Notes—The Office Hydroponic System: An Update
My NFT outdoor hydroponic system looked like a jungle by the time September arrived. As the weeks passed, I knew it wouldn’t be long before I had to wrap it up for another summer growing season. What was I going to do for tomatoes when winter came? Although the hydroponic tomatoes showing up in the supermarkets were big improvements over the gas-ripened, pink, mealy bombs of the past, they were still picked before they were ripe, and they were expensive - $4.99/lb for tomatoes! It was obviously time to get cracking on my second indoor hydroponic system for the winter.
The previous winter, I grew tomatoes in my basement office for the first time. I dubbed that system “Winter I.” It was a small wick system set in a window alcove with two fluorescent lights and a sodium vapor, security lamp. Although, the fixtures didn’t seem to provide quite enough light, mounted inside the window alcove, the tomato vines grew rapidly to the ceiling, 5-ft high.
So, anticipating my need for tomato plants, in September, I started some ‘French Dona’ hybrids and ‘Sun Gold’ cherry tomato seeds in 1-in. rockwool cubes on a tray in the back yard. Everyday or so I checked them and doused them with nutrient solution. Meanwhile, I began planning enhancements to the win-ter system. With Winter I, I used two 4-ft fluorescent fixtures hanging vertically from the ceiling. I called that system the “column of light.” If I was going to add more light, I would need to add more fixtures.
My first thought was just to hang more fluorescent fixtures, but that didn’t seem practical. I fiddled around last winter trying to get the two fixtures, each hung with a single strand of chain, to face the plants. As soon as my back was turned, the lights turned too. I needed something to secure the lights, something that would also help surround and focus the light on the plants.
I looked in the hardware store for something circular on which to mount the lights - No luck. Then I remembered the Hula-hoop craze of the 1960s. I asked my wife Jessica, who knows where everything is, if we still had any old Hula-hoops. Sure enough, out in the shed was an old Hula-hoop, pink- and white-striped and faded. But I needed more than one. I tried the department stores to no avail. Then I found them at a large toy store. The old one from the shed was about 36-in. in diameter. The new one was 27-in. in diameter. Thus the “cone of light” concept was born!
I mounted the four fluorescent fixtures to the two Hula-hoops. But first, I had to remove a panel from the dropped ceiling and screw a section of board between two of the ceiling joists. The Hula-hoops didn’t provide structure, only alignment. Each light fixture was connected to eyelets in the ceiling by a chain. I secured the sodium vapor lamp with small elastic cords in much the same way as the first system. It hangs a little below the ceiling, pointing almost straight down. The space underneath the ceiling provides air flow to keep the plants from overheating.
For light containment, I thought of a material called “super-insulation.” Super-insulation is thin, aluminized mylar. The aluminum film on the mylar makes it reflective. Wrapped in dense layers, it’s used to make extremely effective Dewars to hold liquid helium. It accomplishes this by keeping thermal radiation from getting into the container. You may also have seen it sold as the “space blanket” in the camping sections of stores. A large piece about 48x84 in. retails for around $2.
It took two sheets to swath the light fixtures mounted on the Hula-hoops. The thin 5-mil (1 mil = one thousandth of an inch) sheets made the system look like a space capsule. It was remarkably effective. With all four fluorescent light fixtures lit and the sodium vapor lamp aimed down into the system from the apex, turning off the lights in the basement created a distinct gloom. The light was bouncing around inside the system and wasn’t getting out except for a ring on the floor and the ceiling. All of the photons would be captured by the plants’ leaves and wouldn’t be spent uselessly lighting the room.
The space blankets also maintained the temperature around the plants. With the room ambient at about 72°F, the temper-ature around the plants rose to an equilibrium temperature of about 84°F. As the winter hit with a vengeance, the basement temperatures plunged to the mid-sixties, so the heat was welcomed by the plants.
Meanwhile, I tried to keep the summer system going as long as possible. But the first serious frost came in mid-October. It was time to strike the system. I designed the summer NFT system to be easily erected and disassembled. I had been dragging my feet about taking it down because I was still harvesting a cup full of ‘Sun Gold’ cherry tomatoes everyday. I finally disassembled it in mid-October, and the process only took 30 minutes. I ended up with 12 lb of green tomatoes and hundreds of immature cherry tomatoes.
The nutrient bath for the Winter II system was provided by the same green plastic tub used in the first indoor system. It measures approximately 20x14x9 in. and fit nicely under the cone of light. To promote more rapid growth, I wanted to make the nutrient bath more accessible to the roots. My first thought was to use plastic cups from the supermarket. I cut the bottoms off and covered the opening with 1/4-in. grid material used for hooking rugs. I secured the grid to the bottom of the cups with duct tape figuring that would hold it. I should have known better.
My first system was plagued by leaks and I had tried to seal them with duct tape, generally without success. The tape didn’t respond well to water. I put the plants into the cups and the cups into the tub outside to get it started while I was working on the lights inside. The first day the duct tape let loose, and the rockwool and plants were threatening to sink out of sight into the nutrient.
So then, I cut fairly large holes in the bottom of the cups but left the bottoms on. I cut new pieces of grid that just fit into the bottom of the cups. I rethreaded the wicks, made from an old tee-shirt cut into 2-in. wide strips about 12-in. long, three wicks per cup, through the grid and put the plants and rockwool back into the new cups.
I let the system grow outside for about a week. But it began to get too cold, and I was worried about frost. Because the lamps were in place and tested, I had no more excuses. I purchased a larger plastic container in which to keep the tub, so that if I did spill nutrient it wouldn’t go all over the rug.
One of the keys to hydroponics is to keep on top of the nutrient solution, maintaining an appropriate pH and electrical conductivity (EC). I use a Steiner mix compounded by Total Gro of Winnsboro, Louisiana. In the first indoor system, I mixed up a gallon of dilute nutrient at a time and poured it into the system when it was needed.
This year, I started with the best of intentions to create an automatic nutrient feed system. The idea was to take a feeding-trough float valve, connect it to the nutrient tank, and gravity feed it into the wick-system tub. I bought an extra float valve like the one I had used to keep my NFT tank automatically filled during the summer, but it was too wide and interfered with the cups. It was also awkward to mount.
Instead, I checked the nutrient level each day and, when it fell a couple of inches, I added a gallon of water. Then, I checked the EC with my conductivity meter and, if it fell below 26, I would add an ounce of nutrient concentrate that I mixed from the Steiner solution. One ounce of concentrate translated to a gallon of solution at standard concentration. This system was easy and effective.
To document what I’m doing, two things are indispensable. The first is taking lots of pictures at each stage. Documentation with a camera is simple and fun. If you keep track of when you took the pictures, you’ll have a good visual record of your progress. The second is to keep a log. I use a spiral notebook that has three columns: date, time, and action. A typical entry might look like this:
“12/12/98, 10:40, Counted tomatoes, 22 large ones and a few clusters of cherry ‘Sun Golds.’ Germination seems to have been a bit of a problem.” A more common entry would be something like: “12/15/98, 20:23, Added one gallon of water, no nutrient, EC = 28-32.” Keeping a log, the more detailed the better, lets you go back and review what you did and when you did it.
I also kept track of the plant growth in the new winter system. By mid-October, they were 22-in. tall. A week later, they were 36-in. tall. By mid-November, the tallest plant was 5 ft. As I write this in early January, the plants have all grown to 8 ft and are pressed against the joists of the basement roof.
Whenever I pick fruit from the system, I record it in the log. In December, I harvested 11 ‘French Dona’ hybrids, at an average weight of 4 oz each, and 50 cherry tomatoes. This wasn’t much by the standards of the summer system, but then the outdoor system had about five times as many plants and real sunshine. There is something really special about slicing a ripe red tomato that you grew in the basement when it’s 20°F and blustery outside.
I figure it’s not too early to start thinking about the next outdoor summer system. I have ordered a whole bunch of tomato seeds from Totally Tomatoes. This year, I thought I would try some determinates. I bought four stainless steel sawhorses and two new 4-in. PVC tubes at the end of the summer.
A television show last week on the Home and Garden cable channel featured cold frames. They looked like just what I needed to get my plants going early. I’m also looking into adding instrumentation to the system so that I can monitor the nutrient continuously. One of the reasons I got into hydroponic gardening is that it’s a lot more fun designing systems and growing nearly perfect tomatoes than it is fighting critters and pulling weeds.
Source
Totally Tomatoes
Dept 22
P.O. Box 1626
Augusta, GA 30903