Harvestores are a brand of silo. Silos are as airtight as possible so that the silage--chopped hay or chopped corn--can ferment properly. Once a Harvestore is filled, the finished silage can be removed as needed from the bottom by a mechanical system that cuts into the cylindrical chunk and moves out what's loose. In one famous case, a hired hand got tired of dealing with an inefficient unloader and unbolted one of the blue metal panels so he could use the farm's tractor-like loader to take out larger amounts. This worked very well until the silage above came down in a rush to fill the hole, creating a vacuum at the top, so that air pressure crushed the top of the silo like someone crushing an empty beer can. After serving for most of a year as the laughingstock of the county, the twisted monument to the difficulty of finding good help on dairy farms was taken down.
Vermont farms also use concrete block silos (using specially shaped blocks, not the more usual rectangular blocks) and even, in a few cases, older wooden ones, whose sides are held together by metal bands. But by and large, vertical silos are being replaced by horizontal "bunker" silos, which are cheaper to build and maintain (more on these with a separate picture).
The truck in this picture is making a milk pick-up from a dairy farm--a regular occurrence frequent enough that you shouldn't be surprised if you see it happening while exploring a rural road.