Basically to improve circulation meaning less mold and to make the silo easier to clean. Early tower design often produced a simple, square building with gable roof for ease of construction. However, this shape resulted in inside corners that were difficult to clean and contributed to crop spoilage due to air infiltration inherent to the design. The shift from rectangular to circular form was a natural, early evolution, requiring a corresponding change in roof design from gable to dome as well. This shift also resulted in some intermediary shapes, primarily octagonal, that attempted to meld the ease of angular construction with the storage benefits of a circular design. And in some instances, circular silos were built as retrofits inside the original square building, or planking was placed at angles over the inside corners, to attempt to improve the original design.
If I remember correctly, cylinders are very efficient designs and use the least amount of material and hold the most for their size. Actually, they're actually better than boxes, but boxes stack nicely. Imagine cereal coming in cardboard cylinders instead!
a silo is round because if it were square or had corners dust from the feed would accumilate and you would have to clean it more, because it is a circle the dust doesn't accumulate as fast and therefore doesn't require as much work.
A silo in a round cylinder form is one of the strongest and compact forms for feed storage on a farm....there are seven of them right outside next to my barn. A silo on a farm is usually used for high moisture grain or chopped haylage (feed from chopped alfalfa, timothy, etc) or corn silage (chopped feed from the entire corn plant). It is very important that the structure be in sound condition to PREVENT air from reaching the feed and causing mold/spoilage. For the same reasons, it is also used for liquid storage for products such as fuels, fertilizer, milk (when in short-term holding before pasteurizing, making into cheese, etc.)
so the grain can't collect in corners. that's why all your pots and pans have a radius at the bottom so the food can't get stuck in the cracks, check 'em out.
