Many different types of nozzles are available. Some produce primarily large droplets not subject to drift. However, they would not provide good coverage without using a large volume of material. Others produce a mixture of droplet sizes including many small ones subject to drift. Generally, within any one type of nozzle, droplet size decreases with a decrease in nozzle size and with an increase in nozzle pressure.
A partial list of nozzles and typical uses is given in Table 1. Refer to manufacturers catalogs for descriptions of other nozzles and their use.
Flat fan, regular. Broadcast spraying of herbicides (15 to 30 PSI) and some insecticides (40 to 60 PSI) when foliar penetration and complete coverage is not required. Large numbers of driftable droplets will be produced, particularly with higher pressures and smaller sizes of nozzles. Nozzles are available in spray pattern angles of 65, 73, 80 and 110 degrees. As the angle of the spray pattern is increased, boom height may be lowered. Nozzle patterns should be overlapped by 30 percent (6 inches on a 20- inch nozzle spacing).
Flat fan, LP (low pressure). Broadcast spraying of herbicides (10 to 25 PSI). Larger droplets than regular flat fan.
Flat fan, even. Banding of pesticides over the row or for spraying flat surfaces-walls, etc.
Flooding. Broadcast applications of herbicides and herbicide-fertilizer mixtures (10 to 40 PSI). For uniform application, nozzle spacing should not exceed 40 to 60 inches with a 100 percent pattern overlap. Even though these nozzles produce large drops, they also produce driftable droplets. These can be reduced by operating at pressures less than 20 pounds per square inch.
Hollow cone (low volume). Directed applications of insecticides, defoliants and other chemicals (30 to 120 PSI). Produce small droplets that give good coverage and are subject to drift. May be used with drop pipes supporting two nozzles for row crop application.
Hollow cone disc core (high volume). Foliar applications of insecticides and fungicides at higher flow rates and pressures (40 to 400 PSI). Produce larger numbers of small droplets, particularly at higher pressures. Also used in mist blowers.
Whirl-chamber hollow cone. For soil incorporated herbicides (10 to 40 PSI). Produce large droplets at the lower pressures.
Raindrop hollow cone. Application of herbicides for incorporation. Use where drift is a problem.
RD. Broadcast applications for incorporation at low pressures or foliar applications at higher pressures. Use at low pressures where drift is a problem.