Not sure this would work but a few weeks ago I was thinking about going home for xmas and thought about trying to attach a piece of pvc w/holes drilled in it to the opening of a milk jug (1/2 or 1 gallon),cut the bottom out of the jug,stick the pvc into the soil and fill the jug w/water.I saw something like this on a much smaller scale @ a thrift store awhile back...I think it held maybe a pint of fluid.Early planning stage was as far as I got when I realized I would be too close to my first harvest around xmas.