A differential speed stalk roll assembly (100, 200, 300, 400) mountable to a row unit of a row crop head, comprising: a first stalk roll (110, 210, 310, 410) comprising a first body (112, 212, 312, 412) mounted to a first shaft (113, 213, 313, 413) rotating about a first axis of rotation (117, 217, 317, 417) at a first shaft RPM, the first body (112, 212, 312, 412) having an outer diameter defined by a circle circumscribing an outer periphery of the first body (112, 212, 312, 412); a second stalk roll (120, 220, 320, 420) comprising a second body (122, 222, 322, 422) mounted to a second shaft (123, 223, 323, 423) in lateral spaced relation to the first shaft (113, 213, 313, 413), the second shaft (123, 223, 323, 423) rotating about a second axis of rotation (127, 227, 327, 427) at a second shaft RPM, the second body (122, 222, 322, 422) having an outer diameter defined by a circle circumscribing an outer periphery of the second body (122, 222, 322, 422); wherein the outer diameter of the second body (122, 222, 322, 422) rotates at a speed greater than the outer diameter of the first body (112, 212, 312, 412); and characterised in that at least one of the first body (112, 212, 312, 412) and second body (122, 222, 322, 422) includes at least one annular knife (150, 250, 350, 450) defining a knife plane normal to the first axis of rotation (117, 217, 317, 417) and second axis of rotation (127, 227, 327, 427); wherein the at least one annular knife (150, 250, 350, 450) has an outer diameter that is substantially the same as the outer diameter of the at least one of the first body (112, 212, 312, 412) and second body (122, 222, 322, 422) that includes that at least one annular knife (150, 250, 350, 450). a first stalk roll (110, 210, 310, 410) comprising a first body (112, 212, 312, 412) mounted to a first shaft (113, 213, 313, 413) rotating about a first axis of rotation (117, 217, 317, 417) at a first shaft RPM, the first body (112, 212, 312, 412) having an outer diameter defined by a circle circumscribing an outer periphery of the first body (112, 212, 312, 412); a second stalk roll (120, 220, 320, 420) comprising a second body (122, 222, 322, 422) mounted to a second shaft (123, 223, 323, 423) in lateral spaced relation to the first shaft (113, 213, 313, 413), the second shaft (123, 223, 323, 423) rotating about a second axis of rotation (127, 227, 327, 427) at a second shaft RPM, the second body (122, 222, 322, 422) having an outer diameter defined by a circle circumscribing an outer periphery of the second body (122, 222, 322, 422); wherein the outer diameter of the second body (122, 222, 322, 422) rotates at a speed greater than the outer diameter of the first body (112, 212, 312, 412); and characterised in that at least one of the first body (112, 212, 312, 412) and second body (122, 222, 322, 422) includes at least one annular knife (150, 250, 350, 450) defining a knife plane normal to the first axis of rotation (117, 217, 317, 417) and second axis of rotation (127, 227, 327, 427); wherein the at least one annular knife (150, 250, 350, 450) has an outer diameter that is substantially the same as the outer diameter of the at least one of the first body (112, 212, 312, 412) and second body (122, 222, 322, 422) that includes that at least one annular knife (150, 250, 350, 450).