Potatoes - how deep?

I have been thinking on your question Veggie and I think that it will be a project to work on, I think I will try growing 4 different ways using 1st. bucket with soil as control, 2nd. with a layer of soil then kept topped up with cardboard/paper, 3rd. layer of soil topped up with mix of cardboard/paper and leaves 4th. layer of soil topped up with a mix of cardboard /paper and seaweed all will be fed with a comfrey feed as required, I will also keep a photo record, I might even give vidio recording a try