First, I went to the home center and got a few things. A big sheet of styrofoam, and a big plastic tub.
(Ok, I had the tub already. It is a bit big for this experiment, but waste not want not...)
Next, I flipped the tub over on the styrofoam and traced it out.
Then I cut it out.
Here it is cut and trimmed to size.
Next, I measured, marked, and changed my mind a few times about where the planting holes should be.
And I finally cut them out with a hole saw. It ended up a bit messy. A utility knife would do as well.
Now I can put cups (with holes in the bottom) into the holes to hold some kind of growing medium. I am planning on starting some of my recently acquired seeds (thanks Paradox and Zasso!) into some old rockwool I have lying around. Then I will put some expanded clay pellets or pebble sized rocks around them in the cups.
When the weather is right, I will move it to its final location, fill it with a fertilizer/water mix, tie down the top, and put the cups in. And (if the Kratky method actually works) I will walk away, never look back, and harvest 8 heads of lettuce in 40 days.
- The theory is that you fill it so the cups/pots are sitting 1/3 in the water.
The roots grow down into the water, and as it is used, the water level drops below the pots.
Roots keep on growing down into the solution to get the water, and the older roots and a few newer ones as well get oxygen from the humid air in the gap between the lid and the water's surface.
The method is supposed to be very good with leafy crops like lettuce, spinach, chingensai, etc...
It is better to grow just one kind of crop at a time, as more vigorous plants might strip the water down faster than the less vigorous plants.
After harvest, you can refill and plant again. But after three cycles, they recommend using the leftover fertilizer on houseplants or in the garden and starting fresh.
Of course a balanced hydroponics fertilizer is maybe best (http://www.rakuten.co.jp/eco-guerrilla/ ... ch_conf_02), but you can also use hyponex plant food.
You can do it on a much smaller scale as well. One lettuce plant will use about 4L of water to grow to maturity. So if you have a 4L empty shochu bottle, you can spray paint it opaque and put a plant through the lid. Basically any container will work, providing you can suspend the plant at the top, and prevent algae from growing in it.
I have an old hydroponics book that recommends strips of an unwoven synthetic cloth- like the range hood filter you might use in the kitchen. Cut in strips, put 2 seeds at one end, then wrap the top inch or two with bubble wrap until it is the desired diameter. Then just use it like a cork to stop up the hole. The long strip acts as a wick and keeps the seeds and seedling hydrated. A kitchen sponge folded around can also hold the wick and plant in place. Be inventive.
Search Kratky hydroponics on Youtube and you will see dozens of videos and tutorials. (I recommend mhpgardener)