A comb harrow's main purpose is for weeding crops and reducing chemical costs. It may also be used to break up capped soil or as a conventional harrow for seedbed preparation/harrowing.
Comb harrowing is very effective through cereals, OSR, beans, sugar beet as well as a host of vegetable crops. Not only providing weed control but also aerating the soil. Aerating the soil and breaking the crust assists in water run-off. The combing action stimulates tillering in the main crop as well as releasing surface nitrogen. So, rather than damaging the crop the raking action can improve yields.