As mentioned in Store Garden Produce #10-More on Root Cellaring, Outdoor pits can be either lined or unlined. A lined pit is one that is sealed against ground water and rodents. Figure 1. This typically consists of a 55 gallon barrel or drum or any suitable container such as metal garbage cans or barrels, leaving about 4 inches exposed at the top, that is buried semi-horizontally in the ground. Place 2-3 bushel full of mixed roots in the barrel and put the lid loosely in place to allow for air venting. Cover the barrel with about 12 inches of straw held in place by a 3-inch layer of soil. You can add more straw up to 3 feet deep, depending upon the amount of cold that must be endured by your climate.
In the unlined pit, the roots are piled on a layer of straw and the pile is covered with straw held in place by a layer of soil. The unlined pit must be dug in an area where water will not fill the pit and where rodents are not a problem.
Figure 1: An outdoor barrel storage pit
Using a 55 Gallon Barrel Drum
A storage mound (Figure 2) is similar to an unlined pit. It is used where groundwater is a problem or where only a short storage period under mild temperatures is anticipated. The vegetables are piled on a layer of straw on top of the ground. The mound then is covered with a layer of straw that is held in place by a layer of soil. The mound usually contains one or two bushels of mixed roots, so when the mounds are removed, all the produce can be taken into the house.