In researching hydroponics on the Internet, I ran across something pretty amazing. It’s Kratky Method which is a totally passive, zero electricity method for hydroponics. Yeah, dead simple.

I’ve been working on getting my own hydroponics system setup and have been researching various circulation systems and methods, different layouts, blah, blah, etc. Then I discovered this system that I got setup and started in about an hour one afternoon. As a proof of concept I decided to start very small with just one plant. Apparently it takes about 1 gallon (4 liters) to grow a lettuce plant to maturity. So I found a gallon jug, painted the outside black to prevent algae growth, mixed up the nutrients and “planted” a lettuce seed in rock wool in a 1.5″ basket. The idea is that you fill the container until about the lower 1/2″ of the rock wool is submerged. That will draw the nutrients up through capillary action to the seed. Once the plant starts to grow and the roots reach down, the nutrients recede and the roots chase it to the bottom of the container. The space between the basket and nutrients is where the roots get oxygen as they dangle into the nutrients for food. Add a grow light (or the sun) and that’s it. No air stone, no circualting pump, nothing. And it’s working great.

Now I’m in the process of building a “grow closet” to have whole trays of lettuce and other leafy greens. I found that there are 231 cubic inches in a gallon, so 6″x6″x6″ comes to 216 cubic inches. That should be close enough to grow lettuce then. So I build trays out of wood, to be lined with black landscaping plastic, at 7″x15″x20.5″ internal dimension. If I fill it to an inch from the top, that gives me 1845 cubic inches and 205 cubic inches per plant for 9 plants. I would have built a little bigger, but I was using up scrap material and was a little short. Being 26 cubic inches shy shouldn’t be a show stopper. So now all I have to do is hang the inexpensive led grow lights, fill the tubs, plant the seed and see what happens!

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