Agricultural Spray Nozzles

Field spraying looks simple, fill the tank, drive the rows, pull the trigger. In practice the nozzle is the difference between a uniform, legal, effective application and a drifted, patchy, over-applied one. The decisions that matter are droplet size, which decides drift, and tip wear, which silently changes the rate you think you are applying.

A nozzle does not spray chemical. It sprays droplets of a carrier liquid carrying the chemical, and the droplet size distribution determines almost everything about where that chemical ends up.

Droplet Size and Drift

Fine droplets travel where the wind takes them. Coarse droplets go where you point them. That single relationship, finer droplets drift more, is the central tension in agricultural nozzle selection.

You want fine enough for good coverage and canopy penetration, coarse enough to stay in the field. Anti-drift nozzles resolve this partly by using a pre-orifice that pre-films the liquid before the final orifice, producing a coarser, more uniform spectrum at a given flow than a plain orifice would. Air-induction tips go further, drawing air into the droplet stream so the large, air-filled droplets fall fast and stay in the field.

Spraying on a still morning keeps the fine fraction in the crop. Spraying in a breeze sends it into the neighbour’s field, which is both a efficacy loss and a regulatory problem. The herbicide drift control guide covers the wind-speed rules of thumb in detail.

Coverage Versus Penetration

A flat fan gives an even band across the boom and is the standard for broadcast herbicide work. Cone nozzles, hollow or full, give better penetration into a crop canopy, which matters for fungicides and insecticides reaching the lower leaves.

The choice is driven by the target: soil-applied or early/post-emergence broadleaf herbicide favours the even band; canopy disease control favours penetration. Mixing the two on one boom, with alternating nozzle types, is a common configuration.

The Silent Failure: Tip Wear

Nozzle tips wear. As the orifice enlarges, flow increases at the same pressure, so the sprayer still reads a normal pressure and the operator still dials in the same litres per hectare, but the tip is now putting down more chemical than the rate setting says.

The dangerous part is that it happens gradually and invisibly. A worn ceramic or brass tip can over-apply by a meaningful margin before anyone notices streaks or gaps, by which point the field has received the wrong dose all season. Scheduled tip replacement, and measuring actual output against the rated output, is the control, the nozzle wear guide walks through the measurement.

Range Walkthrough: What Each Tip Is For

The reference table above lists the six tips in one view; this section says when each one is the right answer. All flows are quoted at 3 bar, which is the reference pressure the ISO size system is built around.

AG-02 (ISO 02 flat fan): the low-rate end of the range. 0.79 L/min at 3 bar with a fine droplet class. The tip for low-volume pre-emergence work, narrow-row and spot treatment where a small, even band of fine droplets is wanted. The ceramic orifice keeps the fine geometry sharp, which matters more at small sizes because the same amount of wear removes a bigger fraction of the flow.

AG-04 (ISO 04 flat fan): the default broadcast tip. 1.58 L/min at 3 bar, medium droplet class: the balance point most post-emergence programmes standardize on, with enough coverage for contact work and a spectrum that behaves in a light wind. If a sprayer is set up with one tip for the season, this is usually it.

AG-08 (ISO 08 flat fan, anti-drift): the high-rate broadcast tip. 3.15 L/min at 3 bar, coarse class from a pre-orifice design that cuts drift-prone droplets by 50% or more. For high water volumes, pre-emergence residuals and conditions where the fine fraction has to be kept in the field.

AG-C110 (hollow cone): 0.39–1.58 L/min (ISO 01–04), fine class. The hollow cone throws most of the liquid to the outer edge of the cone, which is what carries fungicide and insecticide down into a closed canopy and onto the lower leaves. Run in its 3–10 bar window; ceramic insert.

AG-C150 (full cone): 1.19–3.15 L/min (ISO 03–08), medium class. A solid, filled cone that combines penetration with even coverage across the whole pattern, the common choice for systemic fungicides and foliar feeding, where the droplet has to land throughout the canopy rather than just at the edge. Stainless 303/316 body.

AG-DUAL (air-induction flat fan): 1.19–3.15 L/min (ISO 03–08), very coarse (C–XC). Air is drawn into the stream and the resulting large, air-filled droplets fall fast and resist the wind; independent testing puts drift reduction at 80–90% depending on size and pressure, with the best performance at or below 3 bar. This is the tip for drift-sensitive boundaries, windy windows and pre-emergence on bare soil.

Application Matrix

Application	Target	Recommended tip	Why
Pre-emergence residual herbicide	Soil surface	AG-08 or AG-DUAL	Coarse spectrum keeps the chemical in the band and off neighbouring land
Post-emergence contact herbicide	Small weeds, broadleaf	AG-02 / AG-04	Fine–medium droplets give the leaf coverage contact products need
Field-edge and drift-sensitive spraying	Any crop near boundaries	AG-DUAL	Very coarse air-induction spectrum, up to 80–90% drift reduction
Fungicide: canopy disease	Cereals, vines, oilseed	AG-C110	Hollow cone penetrates to the lower leaves
Insecticide: canopy contact	Dense crop canopy	AG-C110 / AG-C150	Cone patterns reach undersides and inner canopy
Foliar fertilizer / liquid fert	Broadacre top-up	AG-C150	Medium-coarse full cone covers the canopy and tolerates salt-laden liquor
High-volume / high-rate broadcast	Post-emergence cereals	AG-08	3.15 L/min at 3 bar carries the water volume
Systemic fungicide / growth regulator	Canopy or broadcast	AG-04 / AG-C150	Medium droplets cover without an excess fine fraction

Three-Step Selection

If the full checklist below feels heavy, the decision collapses to three questions:

1. What crop stage are you spraying? The target decides the pattern: soil and pre-emergence want the even band of a flat fan; a closed canopy wants the penetration of a cone; a drift-sensitive boundary wants air-induction. Nothing else matters until this is answered.
2. What drift class does the field allow? Match the droplet class to wind exposure and neighbours: fine–medium for penetration-critical contact work, coarse for pre-emergence and high rates, very coarse (C–XC) where drift has to be near zero.
3. What flow at your boom pressure? The rate in litres per hectare, ground speed and nozzle spacing set the litres per minute per tip, which picks the ISO size. The reference flows are quoted at 3 bar, for any other pressure, flow scales with the square root of pressure, so doubling pressure adds only about 40% flow, not double.

Reference Specifications

Tip wear limits here are typical replacement thresholds, measure actual flow against rated flow rather than relying on visual inspection.

How to Select an Agricultural Nozzle

Work through these in order and the choice usually narrows to two or three options.

• Drift class the duty demands: fine for penetration, coarse for windy or sensitive-adjacent fields.
• Target placement: band (flat fan) versus canopy (cone) decides the pattern.
• Application rate and boom pressure: these set the flow, which sets the tip colour code under ISO 10625.
• Chemical form: some formulations foams or cakes in fine orifices; coarser tips tolerate them better.
• Wear material: ceramic and hardened inserts outlast brass many times over and hold the rate longer.
• Replacement discipline: schedule tip changes and measure output; a worn tip lies about the rate it applies.

Frequently Asked Questions

Why does my herbicide drift into the next field? Likely too fine a droplet spectrum for the wind, or spraying when it was too breezy. Coarse anti-drift tips and a still-wind window are the fixes.

My sprayer pressure is normal but the crop is patchy: why? Patchiness can be a worn tip over-applying in some passes and the rate being wrong overall. Measure actual tip output against rated output.

Flat fan or cone for fungicide? Cone, for canopy penetration to the lower leaves. Flat fan is for the even broadcast band.

How often should I replace tips? On a wear schedule, not on sight. Measure flow periodically; replace at the wear limit before the rate drifts out of spec.

What does the ISO size number mean? The size is the flow class: ISO 02 means 0.2 US gpm at 40 psi, which is 0.79 L/min at 3 bar; ISO 04 doubles it and ISO 08 doubles it again. The reference table quotes exactly these numbers, so the tip name tells you the flow at a glance.

Do I need an air-induction tip for everything? No. Air-induction coarsens the whole spectrum, which cuts drift but costs coverage in a dense canopy. Use them where drift matters, boundaries, windy windows, pre-emergence, and standard flat fans or cones where penetration is the limiting factor.

What pressure should the boom run at? Inside the tip’s window: 1.5–6 bar for standard and pre-orifice flat fans, 1–6 bar for air-induction (best drift cut at or below 3 bar), 3–10 bar for hollow cones, 1–10 bar for full cones. Pressure changes flow, not spray angle.

Why do my tips clog? Fine orifices and formulations that settle or cake are the usual pair. Strainers upstream, coarser tips for suspensions, and ceramic orifices that hold their geometry when abrasive solids pass through.

Not sure which tip fits your sprayer? Send the crop, application rate and boom pressure to the application team and get a shortlist back with flow figures and drift class, not a catalogue number.