Nozzle choice

Choosing and maintaining the correct nozzles has an enormous impact on the accuracy and efficiency of agrochemical application. To select the correct nozzle for the job, follow the steps below

(a) Follow the advice given on the product label (check whether there are any local environmental restrictions or requirements, such as LERAP in the UK)

(b) Check which type of spraying technique you will be using

(c) Select your application rate – Lower rates will increase work rates in arable crops

(d) Check your forward speed – high speeds over 12Km/h will increase your work rate and slower speeds of 8-12km/h are better for penetrating dense canopies

(e) Check your pressure – Finer droplets are produced at higher pressures - individual nozzle charts show this relationship. Always read the pesticide label to determine which spray quality is required.

(f) Select the spray quality that you require. See below.

(g) Select the nozzle style for the required spray pattern

(h) Make sure that you have fulfilled all criteria before you reduce buffer zone widths with LERAP rated equipment.

(i) Check that all constraints have been accounted for e.g. output of your sprayer pump.

Spray Quality

The most important performance characteristic of an agricultural spray nozzle is the size and the variation of droplets or spray quality that it produces.

Conventional nozzles are classified by the droplet size that they produce at a given pressure according to the BCPC International Spray Classification System (e.g. coarse, medium, fine).  

Different air-inclusion nozzles also produce different spray quality but this cannot be determined by nozzle size. For example GuardianAIR nozzles produce smaller droplets than any other AI nozzle. For comaprison of different AI nozzles see the 2010 HGCA Nozzle Chart.

For Hypro nozzles, droplet-size is measured using a Phase Doppler droplet analyser and expressed as the Volume Median Diameter (VMD) in microns (μm). The VMD is droplet size where half of the volume of spray is larger and half is smaller than the stated droplet size.

Spray Pattern

Flat fan pattern

Available as a tapered spray for boom applications or an even spray for single nozzle applications, e.g. knapsacks, they have an elliptical orifice, which produces a narrow oval pattern. Tapered nozzles produce a triangular spray pattern where most of the spray is deposited immediately under the nozzle. By overlapping tapered sprays across a boom an even distribution across a boom can be obtained.

Deflect pattern

Also known as anvil or flood nozzles, deflect nozzles produce wide angled flat pattern when operated at low pressures (around 1-2 bar). The nozzles generally produce a coarse even spray and are ideal for use with knapsack sprayers or applications of liquid fertiliser.

Cone pattern

Nozzles produce either a solid circular even footprint (full cone nozzles) or a hollow circular footprint (hollow cone nozzles). Full cones are ideal for use with knapsacks for spot spraying where as hollow cones are used on air assisted sprayers and traditional boom sprayers when good coverage in dense canopies is required.

Nozzle filters

Sprayers provide filtration at all stages of the spraying system starting with a coarse basket, foot or suction filter at tank filling, medium filtration in front of the pump and finer pressure line filters between the pump and the pressure regulator or between boom sections.

It is also possible to fit fine filters behind the nozzle, perhaps where no pressure line filters are fitted or for very low volume appications. However in practice it may be easier to replace a blocked nozzle rather than replace the filter and it is always advisable to carry replacement nozzles.

Mesh size is important for nozzle filters and recommendations vary with nozzle size;  100 mesh (green) for nozzle sizes 01 and 03, 50 mesh (blue) for 04 to 08 and 30 mesh (red) for 10 to 20.

Filter mesh recommendations are available on all Hypro nozzle charts.

Nozzle filters may be cylindrical which provide the largest screening area, cup filters are an alternative where nozzle holder design dictates and ball check fiters provide some anti drip control where there is no DCV or airstop on the holder.