OK I am going to jump in here. I am not using 5 gallon buckets but 18 gallon Rubbermaid containers for some of my potatoes. Some of my potatoes are in the ground in a 12 inch deep bed with leaves on top. The Rubbermaid containers are about the same height as the 5 gallon buckets. I set the seed potatoes out until they got some sprouts. I used a sodder pencil to burn holes in the bottom of the containers and on the inside I put some fiberglass window screen in the bottom so the potting mix will not drain out. I put 6 inches of soiless potting mix in the bottom. I mixed HollyTone fertilizer (4 tablespoons) in the potting mix and also 2 cups of worm castings. I put 3 seed potatoes on top of the potting mix and then covered the entire thing with dry leaves from my yard. Approx 12 inches of leaves. The potting mix I used is Miracle Grow.

As long as you put about 4-6 inches of a good quality potting mix in the bottom of your 5 gallon bucket and maybe 2 seed potatoes per bucket you should be OK. Straw sounds OK to me. If you want really small potatoes use 3 seed potatoes. I want huge potatoes that is why I only used three in the 18 gallon Rubbermaid.

I like Ronninger's Potato Farm for seed potatoes. I planted Maris Piper, Bintje, Yukon Gold and All Blue. The Maris Piper and Bintje are for frying. Yukon Gold is all purpose and All Blue is for my grandson.

Cheers,
DL