it is!

it looks like the plants in the bucket might be having less success because they wouldn't be getting as much light being down so deep in that bucket. at times in the past when we've planted some annuals in pots and didn't have enough potting soil we'd put chunks of styrofoam or empty bottles with the caps still on in the bottom of the pot to help fill it up. this probably would not work out so great with potatoes as they probably want more space for their roots and tubers, but i've not done potatoes in containers before so i don't know what the lower limit is for them in terms of size of container.