Featured Article:
Growing Notes
May 15 was the last day for expected frost here in the Shenandoah Valley of Virginia and my target date for building a new outdoor hydroponic system. My home-office hydroponic system (see “Growing Notes,” The Growing EDGE, Vol. 9, No. 6) was still yielding tomatoes as spring approached, but I was looking forward to a new adventure.
As I leafed through the Totally Tomatoes catalog reading about the 350 varieties of tomatoes I could try, my mouth watered. The catalog listed big and medium-sized varieties, with exotic names such as ‘Wonder Boy,’ ‘Supersteak,’ and ‘Toy Boy.’ It even had white tomatoes. On page six, a golden cherry tomato, the ‘Sungold Hybrid,’ was pictured and advertised as the “sweetest tomato ever.” So, I sent away for seeds.
A friend told me about a Website from which seeds for the championship tomatoes at the New Jersey State Finals (http://www.njtomato.com/) were being given away. I mailed a self-addressed stamped envelope and waited for my championship tomato seeds to arrive. I could almost taste them (not the seeds, the tomatoes).
While waiting for the seeds, I planned the design for my new outdoor system. The previous summer, I had tried all kinds of hydroponic systems out on the deck. I used NFT, wicks, and various flood-and-drain systems. Although they all worked well, the NFT system was the best. The only problem had been that it leaked because I didn’t anticipate the huge growth of root mass that filled the channels.
This year, I wanted to build an even better, inexpensive, reliable, and easy-to-operate NFT system. Because I still had the components from the old system, I wouldn’t have to buy much more equipment.
Designing the NFT System
NFT stands for nutrient film technique. Some people call it nutrient flow technique. In an NFT system, a medium is used to start the seeds and sometimes is dispensed after the seedling has developed. Nutrient solution flows continuously over the plant roots.
For me, designing a system starts at the nearest hardware and building-supply stores. I take a little notebook along and wander up and down the aisles, writing down anything of interest. This last time, PVC pipe looked promising. If I used pipe for my channels instead of rain gutter, I could seal the ends better and keep the system from leaking. For supporting the channels, I chose two sawhorses to hold two 10-ft sections of 4-in. diameter PVC pipe. I wanted the system to be easy to disassemble and store, so I attached the NFT channels to the sawhorses with easily removable hose clamps.
I bought the tubes at $8.36 each, sawhorse kits at $2.49 each, and four metal-strap hose clamps at $1.43. To dump the nutrient at the end of the channels, I bought two 90-degree PVC elbows at $3.47 each. I planned to use the boards that were left over from last year’s system to build the sawhorses, which cost about $3.31. I also needed end caps. I already had a couple of expensive end caps with threaded covers, but a perfectly suitable insert is available for the PVC pipe at $0.62 each. So my total investment for the basic channels and support is $42.22. To build the system, I had to do some calculating and drilling. I drilled seven 3-in. diameter holes in each PVC tube using a hole saw. To keep the pipe from twisting, I secured it with a clamp. I started the first hole about 8 in. from one end of the pipe and drilled the others every 17 in.
Building the sawhorses took just a couple of cuts with a Skil saw and a little hammering. I decided to put the tubes about 24-in. apart. To mount the hose clamps on top of the sawhorses, I drilled two small holes through the metal and nailed them down. Moments later, I had the sawhorses positioned and the tubes secured in the hose clamps.
An important design step is to make sure that the drain end of the tubes is lower than the feed end. An incline of 1:50 is adequate, although a little more won’t hurt. You want the nutrient to flow steadily to help ensure that the nutrient doesn’t pool and become stagnant. My back yard already has a slight downward slope.
Planting the Seeds
While I was still in the design stages, the seeds arrived. I was particularly excited by the packet that was marked “Super tomato seeds derived from the Giant Standard Tomatoes in the NJ State Finals,” even if it was a little packet with only a few seeds. It was still too cold in April to put the seedlings outside, and my office system was getting out of control. The vines were an incredible tangle and spilled out into the room. So, I decided to sacrifice the office system to grow the seedlings and transplant them outside in early May. Initially, I put the rockwool cubes with the newly planted seeds on a little table in front of the office system.
The Nutrient Feed System
For the nutrient feed, I decided to use the premade drip-irrigation plastic tubes and fittings that are available inexpensively at most garden centers. I bought 50 ft of 1/2-in. plastic tubing for $7.97 and 1/4-in. tubing for the drip fittings. I installed the drip fittings in the first couple of holes at the feed end of the NFT channels.
I resurrected the 26-gal plastic trash can that was last year’s nutrient reservoir and the Little Giant submersible pump with a 7-ft head that was capable of delivering 170 gallons per hour (gph). I looped the tubing from the nutrient tank along the PVC, using elastic ties to hold it loosely in place. I looped the far end back into the nutrient tank and sealed it off with a hose fitting. I then filled the tank with water and ran it on a trial basis.
Everything worked great. The nutrient fed nicely into the tubes and ran back to the tank. I hadn’t thought too much about the top of the tank. You have to keep a nutrient tank dark because light promotes algae growth. While algae don’t consume much nutrient, they make the tank all slimy. I had already put holes in the cover of the previous year’s system, but the holes were in the wrong place. So I just put the cover on upside down, let the water flow into it and overflow the holes, and let it go back into the tank. This turned out to be a mistake.
The Seedlings Grow
Meanwhile, the seedlings were in trouble. They weren’t getting enough light sitting on the table in the office. As they grew bigger, they became leggy: long, spindly, and sickly looking. I was afraid to take them outside because we were still having frosty nights. I tried taking them out during the day and bringing them in at night but it was too little, too late. I was ready to plant, and my plants were dying.
I did the only thing I could do (besides going out and buying plants someone else had started) - I planted new seeds in rockwool and put them outside. In my rush, I didn’t pay much attention to what I planted in what cube. I planted some ‘Sungold,’ the ‘New Jersey Giant Standards,’ some ‘French Dona Hybrids,’ and some ‘Toy Boys.’ I also planted some eggplant. After all, the NFT system had 14 holes to fill. It was now mid-May, and I wanted to get the renegade tomato plants out of the office. I was going to carry them outside, dump the nutrient, put them into plastic bags, and be done with it. I didn’t count on the help of my daughter, Ann Marie, however. She still comes over now and then to visit, bringing my grandchildren with her. She popped in when I was conducting the office purge.
Ann Marie made it clear that putting the tomato plants into trash bags and dumping them was “tomato-cide” and insisted that we should “Save the tomatoes.”
As I took the system apart, I was astounded to find that each of the tomato plants had a mass of roots bigger than 1 ft2. All this time, I thought the plants were root-bound in their pots. Because I just put holes in the pots big enough to pull wicks made out of old undershirts through them, I had only been able to see a slender root coming out of the bottom of the pots. Before Ann Marie began her impassioned plea to save the tomatoes, I cut those roots and pulled the plants out of their pots.
I didn’t think the plants would make it, but Ann Marie was so determined that I told her to go ahead. We put them into 5-gal pots, and she strung an 8-ft vine system along the deck, tying it in place with string. I figured that the plants would die in a couple of days and that would be the end of that. So far, my batting average on prognostication is zero.
Supporting the Plants
To provide support, I constructed an
A-frame with a ridge running the length of the system out of three 8-ft furring strips. Along the strips, I mounted screw-eyes and tied strings to them. When the tomato plant started to grow, I tied the string to the base of the plant and wound the plant around the string. This only takes a few moments every day. Stringing the plants up promotes air circulation around the leaves which cuts down on disease. It’s also easier to pick the tomatoes.
Transplanting
A month or so later, the new tomato plants were large enough in their rockwool cubes to put them into the NFT system. When the cubes were saturated with nutrient, they were heavy enough to stay in place. Over a couple of days, some would tend to drift a little, but this stopped once the transplants were big enough to attach to the strings. I planted 12 holes with tomatoes, one hole with a pepper plant, and one with an eggplant. Once I had the plants in the system, my next concern was to ensure that the nutrient flowed continuously.
Safety
I was concerned about the submerged electrical pump running off of 120-V mains. A hazardous situation could devel-op. Because I have grandchildren running around, I decided to go the extra mile and purchased a special electrical plug that provides ground-fault detection and trips the power if the current doesn’t balance. The plug cost a little more than $40, but the peace of mind was worth every penny.
Nutrient Maintenance
To provide a nutrient solution that would feed healthy plants, I needed to monitor the nutrient concentration and pH level. My municipal water system maintains a fairly constant pH, which is about 6.5 when I mix in the nutrient. It’s not perfect, but it’s adequate and reliable so I have almost entirely dispensed with checking the pH. Your experience will vary depending on your water source.
To measure the electrical conductivity, I purchased a simple meter called the Dip Stick. I dip it into the solution, and the meter lights up a red light-emitting diode next to the appropriate reading. It cost a little less than $100.
Monitoring the solution before I used a meter was rather an involved process. First, I mixed up concentrate from a commercial hydroponic nutrient in powdered form. It usually comes with directions for how much to use per 100 gal of water.
I measured out enough for 128 gal by multiplying the indicated amount by 128/100 - then I measured out this much with a small scale and mixed it into a 1-gal water jug to bring it up to a full gallon. The result was 128 oz of concentrate that made 128 gal of nutrient at the right concentration.
I measured the capacity of my nutrient reservoir and made a list of the depth in inches and the corresponding amount of liquid in gallons. When I measured the depth, I knew how many gallons I would need to fill it again. Whenever I added water to the tank, I measured how much I had to add and then I put an ounce of concentrate in for every gallon added. About every three weeks, I dumped the whole tank and mixed up a fresh tank of nutrient.
A Few Struggles Along the Way
When the backyard system was first up and running, all went well. The plants seemed to grow fine, and I checked the system each morning. Then, the drip fittings started to clog. I thought it was because of plastic chips left behind when I drilled the holes in the PVC pipe. After a few days, however, the problem got worse, and I noticed little green particles on the fittings - algae. There wasn’t a lot of algae in the system, but the holes were small and the algae was building up and blocking the holes.
The algae growth was starting at the upside-down lid on the nutrient reservoir. I probably should have just turned the cover over and cut new holes in the top, but instead I ran a bigger hose. I split the 1/2-in. hose and took half of the flow to the end of one tube and the other half to the end of the other. It tremendously increased the flow through the system and the plants seemed to like it. Now, although I have some algae, it doesn’t interrupt the nutrient flow.
Operation
As the weeks went by, the plants grew fast and luxurious. At first, I only had to add water and nutrient every few days. But as the plants grew, I had to add it more often. Then, as the daytime temperature increased to higher than 90°F and the plants grew taller than 3 ft, the nutrient solution started going down about 10 gal/day. I was fast becoming a slave to my NFT system. When my wife and I wanted to go away for a weekend, we had to have someone come over and put water in the tank and check the nutrient.
I was amazed at how much nutrient the plants were transpiring. I had so many more plants growing in one system that my nutrient consumption was more than double of last year. A mature tomato plant transpires more than 1.3 L of nutrient per day.
I solved the problem with a rather easy expedient. Because I live in a farm community, the hardware stores carry little float valves that are used to keep cattle troughs full of water. I purchased a float valve for $7.99, connected it to the side of my nutrient tank, and now I check for nutrient conductivity once a day.
Results
The plants have grown, flowered, and fruited abundantly. The pepper plant was overwhelmed by the fast-growing tomatoes that stole its sunlight. The eggplant fared somewhat better. The ‘Sungold’ cherry tomatoes flourished. I have been picking about 50 ripe ones every day.
The ‘New Jersey Giants’ fruits have been maturing on average at 11/4 lb. The biggest were 11/2 lb, and one was slightly heavier than 2 lb. All are individual, well-formed tomatoes. I’ve also been getting a beautiful deep-red tomato that is perfectly formed - probably the ‘Dona Hybrids.’
Because I didn’t cultivate the plants to maximize production, such as removing suckers, my yield probably has suffered. But for the whole summer, I only used about 4 lb of powdered nutrient and about 4 gal of concentrate, and I had a great time. The plants removed from the office made it too. This fall, I had about 30 tomatoes ripening on them, after picking tomatoes all summer.
Because they were already bearing when they were put up, we’ve had tomatoes from them since May when we put them out, although it took them a while to recover from the root surgery. The plants in the NFT system caught up and passed them by the end of the summer, and we’ll continue to have tomatoes until the weather gets too cold. The total expenditure for the system was about $100. The ground-fault system and the EC meter added about another $150. The nutrient was about $55 last year and will last at least another five years at the current rate of use. I finally have what I wanted - the system is now a permanent resource. I’ll spend about half an hour stripping it down to be stored for the winter, and it will be ready to use again next year. It sure beats digging and weeding!
Recommended Reading
Hydroponic Food Production, A Definitive Guidebook for the Advanced Home Gardener and the Commercial Hydroponic Grower by Howard M. Resh, PhD, fifth edition, Woodbridge Press, P.O. Box 209, Santa Barbara, CA 93102, 1995.
Commercial Hydroponics, How to Grow 86 Different Plants In Hydroponics by John Mason, Kangaroo Press Pty. Ltd., 3 White Hall Road, Kenthurst, NSW 2156, Australia, 1996.
Hydroponics for Everyone, A Practical Guide To Gardening In the 21st Century by Dr. Struan Sutherland and Jennifer Sutherland, Hyland House Publishing Pty. Ltd., Hyland House, 387-389 Clarendon Street, South Melbourne, Victoria 3205, Australia, 1996.
Hydroponic Tomatoes For the Home Gardener by Howard M. Resh, 1993.
Gardening Indoors by George F. Van Patten, Van Patten Publishing.
Sources
New Jersey Championship
Tomato Weigh-In
Box 123
Monmouth Beach, NJ 07750
Virginia Hydroponics, Inc.
368 Newtown Road, #105
Virginia Beach, VA 23463
(767) 490-5425