BASIC SPRAYING EQUIPMENT: Herbicide tank with by-pass return for agitation. Foot or line strainer. Pump (Nylon roller or vane pump of about 6 gpm generally satisfactory and economical). Pressure regulator and guage. Quick-acting shut-off valve. Hose and fitting (one-half inch satisfactory). Nozzles (fan-type). For most herbicide spraying in crops spray pressures in the range 25 to 40 psi are satisfactory and herbicides should be applied in about 25 to 40 gpa of water. Any combination of tractor speed and nozzle tips to accomplish these pressures and deliveries should be effective. Generally, spray drift is minimized by low pressures and the larger nozzles which deliver coarse sprays. CALIBRATION: Initial calibration of a spray outfit may be accomplished easily by the following procedure. 1. Adjust nozzles, spraying pressure and tractor speed as you wish them to operate in the field. 2. Fill herbicide tank completely with water. 3. With tractor operating as in number (1) above, spray water over a measured course of several hundred yards in a fitted field. 4. Determine amount of water required to refill tank to replace that sprayed. 5. Calculate area sprayed: Width of bands or boom spread times distance. 6. From 4 and 5 calculate quantity of water applied per acre. 7. Rate of application per acre can be decreased by: using smaller nozzle tips, less pressure or faster tractor speed. 8. Rate of application per acre can be increased by: larger nozzle tips, higher pressures or slower tractor speed. 9. When calibration is satisfactory add required quantity of herbicide per acre to amount of water applied per acre by the spray unit.