Several people have asked about the earth pits we used in Idaho to preserve various vegetables throughout the very cold winters.
These were simple pits that we dug by hand with a shovel that were about two feet wide, five or six feet in length, and three to five feet deep. Our soil was easy to work with and we could dig these holes quite rapidly. We filled each hole with the foods we wanted to preserve through our cold winters, such as carrots, potatoes, onions, beets, and so forth. We filled them until the food reached about six inches to a foot or so from the top of the hole. Then we covered them with insulation of some sort. We always used straw topped with a blanket; however any quality insulation will work.
When the snows came they would cover the blanket and create greater insulation against the harsh cold. The ambient temperature of the earth would keep the produce warm enough to keep it from freezing. This worked well for all root vegetables. In principle, it probably would have worked well for squashes, apples, pears, and all the various Fall harvest crops too, but we stored the fruits and squashes in our pump house for greater convenience.
We always used a blanket on top because it made it so much easier to move the snow aside to get into the produce. Then when it was time to cover things back up, we weren't adding snow to the straw. We would just lay the straw back in nicely, cover the straw with the blanket again, and then pile the snow back on evenly.
Whether we needed more carrots, potatoes, or onions we would remove a couple weeks worth of produce, and then would cover it all back up again. During the several harsh winters I lived in Salmon, Idaho I don't recall having even one piece of produce freeze when stored in this manner, nor did we have any that rotted. The key was to always keep things dry in the pit and to keep it well insulated.
It is a practical and affordable way to use the ambient temperature of the earth to preserve food throughout the wintertime. If you want to do something similar, I would call the Ag Extension Office in your area and discuss food storage earth pits based upon your area. I've shared the basics with you here, but those basics may need to be adapted to your location for depth of the pit. Weather factors can change the outcome. In our area, even though it was very cold and we had plenty of snow, it remained dry in the ground all winter. A wet drippy climate might require a modified approach.
For emergency preparedness and practical living suggestions, this is a simple and affordable solution to share with friends and family.