The system has a machine (2) for comminution of pieces of field crops supplied by another machine (1). A machine housing is provided with an upper filling hole and a discharge hole (8) underlying in a working position. A drum (9) is rotatably arranged in the housing and carries cutters (10) radially protruded from a casing of the drum. The cutters form a field crops comminution unit with a comb-shaped counter blade (11) arranged at an inner wall of the housing. The discharge hole is provided at the counter blade in a rotational direction of the drum.