A Simple Root Cellar
Some of the most overlooked aspects of food storage are the old-time ones that work just as good as new processes, but for whatever reason have been relegated to the "way it used to be" category. A simple root cellar stands out among these because when the words are spoken visions of major construction projects quickly eliminate the idea from further consideration. What we're referring to here is not the underground room that you travel down a flight of stairs to enter, but rather a storage box imbedded into the ground that preserves food in the same manner as it's massive counterpart.
The appeal of making these lies in the simplicity of making them - nothing more really than a 4 foot long by 2 foot wide 2 foot deep box made of 5/8 inch thick plywood with an affixed bottom with either a hinged or removable lid. A hole is dug in the ground to a depth of 36 inches and of a length and width about 6 inches larger than the plywood storage box. The bottom of the hole is lined with 4 to 6 inches of gravel or rock, the storage box is inserted into the hole and the space surrounding the sides is filled in with gravel or rocks also.
The storage box can be filled with potatoes, onions, carrots, beets, squash, or apples and then a thin piece of Styrofoam is laid on top before placing the plywood lid closed. Examine each piece of produce closely before placing it into the storage box to assure that they are clean, dry and have no signs of spoilage such as soft spots. The adage "when in doubt throw it out" is the golden rule here, as one bad piece of produce will ruin the contents of the entire storage box quickly. Your mini-root cellar can now be covered with a tarp and camouflaged to avoid detection.
If done properly this type of mini-root cellar can keep produce edible from fall until mid to late spring inexpensively (think of the hundreds of mason jars it would take to store the same volume of food). Best of all each storage box can be reused each year - boxes usually last at least 3 years for untreated plywood and 5 years or more for treated plywood.
Good Links - http://en.wikipedia.org/wiki/Root_cellar