Pressure circulation system (DUS) guarantees the fluid circulation within the entire system. Before work, all the hoses including the spray lines are flooded with spray agent under pressure in the reverse direction. With pressure circulation system the spray lines are always filled over the entire working width and instantly ready for use. By sections shut off, during the turning and during transport, the spray liquid circulates continually. This prevents deposits, blockages or segregation in the spray lines. The concentration of the spray agent always remains constant right up to the nozzles, so the start of spraying is carried out without any problems after a change of ingredients. During the cleaning operation, fresh water flushes the spray lines out up to the nozzles, without any spraying. During this cleaning procedure the concentrated spray liquid is returned back to tank.