DWC Hydroponic System Question

by Cody
(Carbondale, CO)

I have been looking to build an NFT system, a lot like the one your have on the site here, with the sloped PVC and constant flow. The only question I have been unable to come up with a good answer on my own is how do you "plant" the plants in the system?

I know you put the plants in the holes in the PVC, and I know that the roots must be in the flow of water, and I also know that you must have capillary mat in the bottom of the duct, but how do you keep the plants from washing away into the tube when they are first planted?

Can the plants be placed into net cups filled with clay media? Do they need to be planted into tight fitting styrene foam? Or do they just sit in the water on the mat, and hope for the best?

Thank you very much for your help. Your site is excellent, and I have learned a LOT about hydroponics and what it takes to keep plants alive. I am in the process of building my first system, and I hate to say it, I think I am hooked. There is no end in sight! Thanks again! Cody.

Answer: I remember when I first got hooked. It really is a great (and rewarding) hobby. Plants always need a certain amount of physical support. For seeds and clones, I usually use Rapid Rooter plugs. I used to use round rockwool plugs, but have found over the years that the Rapid Rooter plugs are more trouble free. Once you have seedlings or clones several inches tall (either in Rapid Rooter plugs or in rockwool plugs), it is very easy to transplant them into netted pots filled with expanded clay pellets.

The expanded clay pellets are there only for physical support. It is important that you pre-soak the clay pellets for a minimum of 20 minutes, so they absorb a proper amount of water. Otherwise, they may dry out too soon and damage the delicate roots of fresh transplants. Obviously, your netted pots need to fit nicely into the holes you cut in your hydroponic system.

I believe the hydroponic system you refer to on my site is my most successful system. In this system, I do not use any capillary matting at all. Instead, I keep a high water level inside the tubes, which keeps the roots constantly submerged in nutrient solution.

Instead of netted pots, I made my own from 16 ounce disposable "party cups" using a soldering iron. The fumes from melted plastic are highly toxic, so be sure to do this only in a well ventilated area if you decide to go this route- seriously! Follow the link above- on that page I include some specific directions on how to transplant your Rapid Rooter plugs into the pots full of clay pellets.

Basically, you do not want the roots of your seedlings submerged at first. You add just enough clay pellets (to the netted pots) to let the root ball sit just above the water level, which allow the plants to grow down into the system very quickly. Fill the rest of the cup around the seedlings with clay pellets for physical support. As long as you pre-soaked the clay pellets properly, they should stay moist just long enough to let the new plants grow their roots down into the system. You should never have to water the clay pellets again after that.

There are other ways to support the plants. I have considered making this same hydroponic system with much smaller planting holes....mainly because it is tricky keeping the water level high in the system without causing little leaks out the bigger planting holes here and there. With a small enough netted pot (3/4 inch), I could envision putting a Rapid Rooter plug straight into the netted pot, than straight into the hydroponic system. This would eliminate the need for clay pellets, but I could not say how well it would physically support the plants once they began to grow.

At some point, if your plants grow too large, they may need additional support. For shorter plants, keeping an oscillating fan on them usually makes them strong enough to support themselves. Larger plants can be tied up or supported by a grid of string somehow (tied off to a wooden frame around the perimeter of the garden?).

In all fairness, the homemade system on my website (the one I linked to above) functions more like a deep water culture (DWC) than a nutrient film technique (NFT)- which is why I changed the name of your question. Just remember to keep an air pump or two in the nutrient reservoir whenever you try to grow plants in standing water. I sure hope this helps you out Cody, and Happy Growing!