Modern agriculture relies heavily on pesticides and herbicides in order to meet the needs of a growing world population. The safe and effective application of these substances is important both to crop production and to environmental protection. Spray drift of either pesticide or herbicide can damage untargeted crops, damage the environment and reduce the effectiveness of the treatment on the targeted crops. Selection of the proper spray nozzle is an important way to reduce spray drift.
Flat-fan nozzles are used for spraying herbicides and some pesticides. Standard flat-fan nozzles operating between 13.6 and 18.1 Kilogram per square inch (PSI) produce an oval, tapered spray pattern of medium-sized droplets that are not very susceptible to spray drift. Low-pressure flat-fan nozzles are designed to be operated between 15 and 20 PSI and produce larger droplets even less susceptible to spray drift. Even flat-fan nozzles differ from the standard flat fan in the shape of their spray pattern. Rather than the standard oval pattern, the even flan-fan nozzles produce an even band of coverage. Adjusting the angle and height of the nozzle controls the bandwidth. These nozzles are not intended for broadcast applications. Extended-range flat-fan nozzles operate at a wider range of pressures, between 15 and 60 PSI, making them particularly useful for flow-controlled sprayers. At pressures below 25 psi they have excellent drift control. Off-centre flat-fan nozzles are used as the end nozzles on spray booms, and twin-orifice flat-fan nozzles produce two separate spray patterns for improved coverage and penetration.
Full-cone nozzles operate between 15 and 40 PSI and produce large droplets with low drift potential. They are particularly useful for herbicides that are incorporated into the soil, and for flow-controlled spray systems. Hollow-cone nozzles are designed to operate between 40 and 100 PSI. The higher pressures produce a smaller droplet that increases the risk of spray drift. The smaller droplets provide better foliage penetration and leaf coverage, but because of the drift risk these nozzles should not be used to apply herbicides. Fine hollow-cone nozzles produce an atomised spray and are used to provide the complete coverage of plants or weeds required by some post-emergence herbicides.
Flood nozzles operate between 10 and 25 PSI and produce large droplets. Operating pressure and the spacing of the nozzles determine the shape of the spray pattern. They are used primarily for the application of soil-suspended fertilisers and soil-incorporated herbicides. The large droplets provide for excellent drift control and help to reduce clogging.
Raindrop nozzles operate between 20 and 50 PSI and produce large droplets at all pressures. They are particularly useful for applying soil-incorporated herbicides and may be directly mounted on the tilling equipment. The droplets are too large for use with non-incorporated herbicides, but they can be used for broadcast spraying.
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