The leaves and heads of the sugar beet are cut off with the beet topper (1).
It can be a large knife with a convex curved blade and a straight handle, such as a bread knife or a piece of the blade of a scythe with the point broken off (2). In another model, the blade is trapezoidal and the edge is straight.
The beet topping hoe or the mechanical beet-cutter is also used for the same purpose. [MOT]
(1) According to V.A.W.P.: 1.360, there are also tools in the form of a vegetable chopping knife for that purpose.
(2) Eg. JEWELL: 15.