I came up with an idea to use a couple of 5-gallon plastic buckets to approximate an Earthbox-type planter. The buckets happen to stack with about 4 inches of space between the bottoms of the two. This space will serve as a water reservoir.

I cut a 3-1/2-inch hole in the bottom of one bucket, as well as 16 3/8″ holes for soil aeration. A 16-ounce plastic Solo or Dixie cup placed in the hole serves as the “wick” for the potting mix to absorb water. Cutting slits in it allows the water to pass through.

The only mod to the lower/outer bucket was to drill a 3/8″ hole in the side just below the bottom edge of the upper/inner bucket, to serve as an overflow and to allow air in. One of the 3/8″ holes near the edge of the inner bucket was enlarged to accept a length of 1″ rigid plastic
aquarium tube for a water fill tube. I purchased a single bucket lid, in which I cut a 3″ hole in the center for a single tomato plant, and also a 1″ hole to accomodate the watering tube. Before putting the lid on, I spread about a cup of granular fertilizer in a thin ring around
the outer edge of the surface of the potting mix. Then the lid was put on and the tomato plant was planted thru the center hole. Should be enough to sustain a single plant for an entire season.

Project cost: Buckets $2.50 (x2); lid $.97; 1″x18″ tube $1.50; plastic cup free; 25 dry quarts potting mix $2.99; 1 cup dry fertilizer and 1 cup hydrated lime (to condition soil for tomatoes) ~ $.50. Total approx. $11.00.