A chopper (1) comprises a framework (3) and a chopping drum (14) rotatably mounted in the framework (3). The drum (14) comprises a plurality of cutting blades (31) radially extending from and circumferentially spaced apart around the drum (14). Each blade terminates in a longitudinally extending cutting edge (48). A pair of pressure plates (51) urged by compression springs (53) towards but not against the drum (14) define with the drum (14) a passageway (28) for the passage of material to be chopped. The drum (14) and blades (31) co-operate with the pressure plates (51) for chopping material in the passageway (28). Stop members (63) extend from the pressure plates (51) and engage members (62) for retaining the pressure plates (51) spaced apart from the drum (14) and the cutting edges (48) of the blades (31). A hopper (70) delivers material to be chopped into the passageway (28). The chopper (1,84) may be mounted on washing and chopping apparatus (80) for washing and chopping fodder beet.