The storage of grain in underground pits is one of the oldest systems known, used since remote times in South Asia. In Malta, grain is traditionally stored in large vase-shaped underground pits lined with straw. In Israel, Donahaye and co-workers improved this system by lining the pits with polyethylene sheets. They obtained good results with rye stored for 15 months. These researchers consider rodents as the possible limiting factor for this type of storage.
Underground pits allow hermetic storage conditions.
The principle is that decreasing the concentration of oxygen and increasing that of carbon dioxide via respiration of grain and of insects eventually cause the insects to become inactive, and will sometimes kill them. Experiments have demonstrated that either a reduction in oxygen or an increase in carbon dioxide will kill insects within hours or days, depending on the concentrations of oxygen and CO,, the insect species, and on factors such as temperature and moisture content in the grain. It is also known that the degree of hermetic sealing required to prevent growth of fungi is much more critical than that needed to control insects in dry grain, where light infestation can sometimes be tolerated. An experiment was set up to see whether fumigated, de husked maize with low moisture content could be successfully stored in an underground pit lined with locally available, fairly thin polyethylene. This system was developed for use on small farms.