A header (14) for an agricultural harvester (10) includes a plurality of row units, a plurality of feed/snapping units (26), and a plurality of chopping units (34). Each feed/snapping unit (26) is associated with a respective said row unit and operable at a first operating speed. Each chopping unit (34) is associated with at least one respective feed/snapping unit (26) and operable at a constant second operating speed, independent of the first operating speed.