Beet knife it is. The thing on the end is called a pike; it is used to pull the root of the beet out . It is then held by the root part in the left hand and the tops severed with the blade. This of course is backbreaking work that has been replaced by a machine in all but the smallest farms. And, of course, many of the small organic farm-to-fork producers will sell the beets with the tops still on.