Abstract: For spraying orchards or other agricultural products, apparatus is made up of modular components including a discharge head unit, a tank unit and a draw bar unit. In one mode of use, the discharge head unit is supported by the three-point-hitch of a tractor, and the draw bar unit is mounted on the tank unit for coupling the tank unit to a hitch mounted on the head unit. In another mode, the tank unit, discharge head unit and draw bar unit are assembled in a unitary trailer assembly to be towed by a towing tractor. In each case power is supplied by the tractor power takeoff. The discharge head unit includes a centrifugal blower including a generally cylindrical housing and a generally concentric blower rotor, with high velocity discharge nozzles projecting generally radially from a generally cylindrical housing wall portion. The housing is constructed so that the nozzle wall portion is readily removable and replaced with a substitute nozzle wall portion containing a different nozzle arrangement.