The Growing Edge Arrived ...

I got my copy of The Growing Edge Vol. 20 No. 2 November/December 2008 just yesterday and it has a nice article by me in it about getting started in hydroponics. Simple systems allow a person to get started in hydroponics pretty easily. It doesn't get any easier than a wick system or a float system. Pick up an issue and take a look. There are even a couple of pages from my notebooks.

More on Passive Systems

This is the time of year (mid-October) when my mind tends to turn to system design. What should I do next year. I've had two pretty tame Summers since I've taken a vacation last Summer and this Summer I worked on a study of image-processing and the Shroud of Turin which I hope will be up on the Ohio Conference Shroud site by the end of December. That tends to mean that next Summer it's back in harness growing tomatoes. But I want to take some time and drive around and visit some folks and now that our youngest son has gone off to the Navy there's no-one to tend the hydroponics system when we're away.
"If anything can go wrong it will" is one formulation of Morphy's Law, so leaving a hydroponics system to its own devices when it depends on the electrical mains is a recipe for dead plants. So I've been thinking about passive systems. I've mentioned wick and float systems. One passive system I've mentioned only in passing is the Auto-Pot system which uses a clever little device known as a Smart-Valve. Jim Fah invented this gadget and you can read about it HERE.

Jim Fah's Smart Valve and the Auto-Pot System

The Smart-Valve is the "brains" of the Auto-Pot system. It consists of a couple of interconnected float valves that both limit the height of the nutrient fed to a plant and prevent new nutrient from being added until the level drops to a predetermined lower depth. This little trick nicely simulates the way plants experience nutrient in the real world of dirt growing. I used one of Jim's valves on the Deck System long ago in Summer One and it worked just fine. I chose to use NFT instead in the intervening years, but I've always had a soft spot in my heart for passive systems. So a week or so ago I bought two of Jim's latest valves and I'm going to test a mix of passive systems this coming year to see just how much difference it makes to the plant to simulate the real-world nutrient cycle.

Passive Systems

Passive hydroponics systems have a lot of advantages. You might ask: "What's a passive system?" The short answer is one that doesn't need electricity to operate. The two easiest passive systems are 1) wick systems, and 2) float systems. There is a third form of passive system which is a bit more technically sophisticated, but not much, called an Autopot system. Let me quickly summarize each.

Wick Systems

Wick system are two level systems. The nutrient is in a tank below a cover and the plant is mounted on the cover with wicks which go down into the nutrient tank. The nutrient feeds up to the plant by capillary action and the roots of the plant follow the nutrient moisture down into the tank. It is completely passive and very easy to construct. Plants don't typically grow as vigorously in a wick system as they do in an NFT system, but they do well.

Float Systems

Float systems are usually best suited for plants that are fairly light since heavy plants with substantial support requirements will tend to weigh down the floats and submerge the system or the floats will have to be large. I have used floats very successfully to grow basil and lettuce. You get Styrofoam sheets to make the floats and cut holes for little plant cups in the foam. Since the system actually floats on the nutrient the bottom of the cups are in the nutrient so while you could use wicks they are generally unnecessary. Rather quickly the roots grow down into the nutrient. You can oxygenate the solution using aquarium air pumps but then you need electricity. My experience suggests that if you design your plant cups so there is a relatively dry interval they can get oxygen via that route. There's a photo of a float system growing basil in the sidebar.
I'll leave the Autopot system for my next post, since it is more complicated and deserves its own discussion.