The following is from Putting Food By and my father:
A root cellar is the best storage place for potatoes and other root crops - it has relatively constant temperatures and high humidity (80% or better). In the absence of a root cellar, one could use any place that duplicates these conditions (low or no light, constant temps. around 40 degrees F, and 80% relative humidity). Potatoes need to be stored in low temps so they will remain dormant and not sprout prematurely. They also need to be protected from drying out. And we all know what happens when potatoes are exposed to light (they turn green and produce a toxin that is not entirely healthy for consumption, though not deadly). Given that, keep in mind that potatoes do not freeze until the temp drops to 30 degrees F. They tend to sprout after a few weeks of exposure to temps above 50 degrees. So the desirable temp can be considered as a range between 30 and 50 degrees F.
The method I will use this winter will be to turn a 5 gallon bucket on its side and cover it with hay or straw (mulch). This mulch will be built up from behind and beside the bucket until it is twice as high as the bucket alone. I will place a small amount of mulch on the new bottom of the bucket and arrange the potatoes in a single layer and then alternate mulch and potatoes until the bucket is full. Then I will place a piece of 3/4 inch plywood in front of the bucket and cover with mulch. If I get enough snow this winter, I may use snow in front of the plywood instead of mulch.
I will actually use several buckets since it is not a good idea to store different varieties together in the same bucket and I plan to save two varieties of regular potatoes and sweet potatoes. A 5 gallon bucket is not a "magic" container, just what I happen to have on hand. Putting Food By suggests using a 55 gallon drum! Also, this method is usually called 'pit storage' though that is a misnomer since no digging is involved (except digging the tubers in the first place).
Offered by Roger.
Here's a new page I've just added to my web site. It concerns Root Cellars, which were once an essential part of the subsistence chain. Whether we'll be able to get to this level after the shift is another question, but the information is valuable nonetheless.
Offered by Mike.