trench silo

A trench silo is a type of agricultural structure used for storing silage, particularly in regions with low rainfall. It is essentially a trench, sometimes dug into a bank or slope and occasionally lined with concrete.1

Silage is a type of fodder that has undergone partial fermentation, making it edible for farm animals. Silos, in general, are airtight structures designed to protect silage and maintain its succulent, slightly sour condition. While upright cylindrical towers are common, silos can also take the form of horizontal pits, trenches, or stacks, either above or below ground. To preserve the silage, the structure must be sealed to keep air out.2