6.1 Application Equipment and Nozzle Selection
Key Takeaways
- The four main nozzle families are flat-fan (broadcast herbicides), hollow-cone (insecticides/fungicides and canopy penetration), full-cone (higher-flow soil-directed work), and flood/air-induction (drift-reducing, systemic herbicides).
- ASABE S572.3 classifies droplet spectra from Extremely Fine through Ultra Coarse; Fine droplets drift most, while Coarse to Ultra Coarse droplets cut drift-prone fines by 50-80% versus standard flat-fans.
- Nozzle material determines wear life: brass and nylon wear fastest with abrasive wettable powders, while stainless steel, hardened stainless, and ceramic last longest and hold calibration.
- Correct boom height and 30-50% nozzle pattern overlap at the target surface are required for uniform broadcast coverage; too low gives streaks, too high increases drift.
- Screen mesh must match the nozzle: 50 mesh for flat-fan and flood nozzles, 80-100 mesh for cone nozzles; a clogged or wrong-size screen starves the nozzle and distorts output.
6.1 Application Equipment and Nozzle Selection
Quick Answer: Match the nozzle to the job. Flat-fan nozzles broadcast herbicides; hollow-cone nozzles apply insecticides and fungicides where canopy penetration and fine coverage matter; air-induction (venturi) nozzles produce Coarse to Extremely Coarse droplets that cut drift by roughly 80% and are preferred for systemic herbicides and drift-sensitive Iowa fields. Nozzle material controls wear life, and correct boom height plus 30-50% pattern overlap guarantee uniform coverage.
Sprayer Types
Iowa applicators use several sprayer platforms, each suited to a setting:
| Sprayer Type | Typical Use | Key Trait |
|---|---|---|
| Boom sprayer | Field crops, broadcast herbicides | Multiple nozzles on a horizontal boom; most common for row-crop work |
| Boomless / cluster | Pastures, ditches, non-uniform terrain | Wide swath from a single cluster; fewer nozzles to maintain |
| ATV/UTV spot sprayer | Small acreage, spot treatment | Low-flow 12V pump; useful for fence lines and odd shaped areas |
| Backpack sprayer | Small sites, hand-held work | Manual pump; calibration still required |
| Hand-gun / high-pressure | Rights-of-way, brush, ornamentals | Operator-controlled trigger; swath depends on operator speed |
| Granular applicator | Dry herbicide, insecticide bait, fertilizer | Drop or spinner spreaders; calibrate by gate opening and travel speed |
Regardless of platform, every sprayer delivers pesticide through nozzles that meter flow, atomize the liquid, and shape the pattern. Nozzle choice sets the droplet spectrum, the application rate, and the drift risk.
Nozzle Types and Their Patterns
Flat-fan nozzles produce a tapered-edge fan that, when overlapped with adjacent nozzles at 30-50%, gives a uniform broadcast band. They are the standard for soil-applied and postemergence herbicides in Iowa row crops. Extended-range flat-fans widen the usable pressure window so a single nozzle holds a Medium to Coarse droplet across roughly 15-60 psi.
Hollow-cone nozzles spin the liquid through a core and orifice to produce a ring of fine droplets. The fine droplets give excellent coverage of leaf surfaces, which is why hollow-cones are preferred for contact insecticides and fungicides. They also produce the most drift-prone droplet spectrum and require higher pressure (40-100+ psi).
Full-cone nozzles deliver a solid cone of larger droplets at higher flow rates. They are used where coverage plus higher volume matters, such as soil-directed insecticides or banded applications over the row.
Flood (flooding fan) nozzles emit a wide, flat, relatively coarse pattern at low pressure. They are simple and resistant to plugging, which suits suspension formulations and broadcast soil treatments, though pattern uniformity is lower than a true flat-fan.
Air-induction (venturi) nozzles draw air into the liquid stream through a venturi port. The resulting large, air-filled droplets are classified Coarse to Extremely Coarse and cut drift-prone fines by roughly 80% compared with an extended-range flat-fan. They are the go-to nozzle for systemic herbicides (glyphosate, 2,4-D, dicamba) and for any application near sensitive Iowa sites where wind cannot be avoided. The trade-off is reduced coverage on small weeds or contact products.
Nozzle Material and Wear
Nozzle orifice wear enlarges the tip and raises flow, silently driving the application rate above the label. Material choice dominates wear life:
| Material | Wear Life | Use |
|---|---|---|
| Brass | Shortest | Clean water, low-abrasion work; cheap but wears fast |
| Nylon / polymer | Short | General use; swells with some solvents |
| Stainless steel | Long | Abrasive wettable powders, flowables |
| Hardened stainless | Longer | High-use commercial rigs |
| Ceramic | Longest | Heaviest use; highest cost but best calibration stability |
Check nozzle flow at least seasonally; replace any nozzle that exceeds 110% of its rated output, and replace the full set if the average is more than 10-15% above a new tip of the same size.
Droplet Spectrum (ASABE S572.3)
The American Society of Agricultural and Biological Engineers S572.3 standard classifies spray by Volume Median Diameter (VMD, also written Dv0.5) into the categories below. Fine droplets lose velocity quickly and drift; Coarse and larger droplets resist drift but cover less surface area per gallon.
| Category | Symbol | Approximate VMD (microns) | Drift Risk |
|---|---|---|---|
| Extremely Fine | XF | <60 | Very high |
| Very Fine | VF | 61-144 | High |
| Fine | F | 145-235 | High |
| Medium | M | 236-340 | Moderate |
| Coarse | C | 341-403 | Low |
| Very Coarse | VC | 404-502 | Low |
| Extremely Coarse | XC | 503-665 | Very low |
| Ultra Coarse | UC | >665 | Very low |
Higher pressure shifts the spectrum finer; lower pressure and larger orifices shift it coarser. Always match the droplet category to the label, which may specify a minimum droplet size for drift-reduction.
Nozzle Spacing, Overlap, and Boom Height
For a broadcast boom, nozzles are typically spaced 15, 20, or 30 inches apart. The fan angle (commonly 80 or 110 degrees) plus the boom height set the overlap at the target. A flat-fan pattern is tapered at the edges, so adjacent nozzles must overlap by 30-50% at the leaf or soil surface to avoid streaks. As a rule of thumb, a 110-degree flat-fan at 20-inch spacing runs a boom height of about 15-18 inches above the target; an 80-degree tip at the same spacing needs roughly 18-22 inches. Raising the boom widens the swath but increases the time droplets are airborne and the drift risk.
Screens and Filters
A strainer protects the pump; line and nozzle screens protect the nozzle tip. Screen mesh must match the nozzle: use 50 mesh for flat-fan and flood nozzles, and 80-100 mesh for cone nozzles. A mesh that is too fine for the formulation will plug; one that is too coarse lets debris through and wears the tip. Always run a filter between the tank and the boom, and clean screens during calibration checks.
Selection Checklist
- Read the label for required droplet category, pressure, and spacing.
- Pick the nozzle family that matches the pesticide (systemic vs contact).
- Choose an orifice sized for the target GPA at your travel speed.
- Pick a material that survives the formulation's abrasiveness.
- Set boom height to give 30-50% overlap at the target.
- Match screen mesh to the nozzle type.
- Calibrate before spraying and after any change of nozzle, pressure, or speed.
Which nozzle type produces the coarsest, most drift-reducing droplet spectrum and is preferred for systemic herbicides near sensitive Iowa sites?
A nozzle whose output has risen to 112% of a new tip of the same size should be: