Spray rig nozzles and farm sprayer nozzles: match the pattern to the agricultural target
The nozzle sets the amount of spray applied to an area, the uniformity of the spray, the coverage on the sprayed surfaces and the amount of drift. The types in common use for ground application are the regular flat fan, the even flat fan and the cone nozzle.
Regular flat fan: broadcast herbicides
Regular flat-fan nozzles are used for most broadcast spraying of herbicides. They make a flat oval pattern with tapered edges, come in 65, 80 and 110 degree fan angles, and are usually spaced 20 inches apart on the boom at a height of 15 to 24 inches. The normal operating pressure is 20 to 30 psi, which gives medium to coarse drops.
Because the pattern edges are tapered, neighbouring patterns must overlap. The most uniform pattern comes from an overlap of 50 to 60 percent of the nozzle spacing. Spraying clean water onto concrete and watching the drying pattern shows the overlap.
Even flat fan: banding over the row
An even flat-fan nozzle applies uniform coverage across the whole width of its pattern and is used for banding chemicals over the row. It runs at 20 to 30 psi, and nozzle height sets the band width.
Full cone spray nozzle: canopy penetration, not broadcast herbicide
Cone nozzles are used when foliage penetration is essential for insect or disease control and drift is not a major concern. At 40 to 80 psi they make small droplets that cover the underside of leaves better than any other nozzle type. A hollow cone puts the spray in a ring.
Cone patterns are very susceptible to drift, and the nozzles are very difficult to arrange along a boom for uniform distribution, so they are not recommended for broadcasting herbicides.
Spray nozzle for a weed sprayer
For a weed sprayer, flat-fan nozzles are the broadcast herbicide choice and are also used for banding herbicides. Flooding-type and full cone nozzles used for pre-plant herbicides produce large, drift-resistant droplets, and they allow wide nozzle spacing. Hollow cone nozzles make smaller droplets and are used for insecticides and contact herbicides that must penetrate the canopy. Pick the pattern first (broadcast, band or spot), then check flow and droplet size against the product directions and the nozzle chart.
Boomless sprayers
A boomless low-pressure sprayer has a central nozzle cluster that produces a horizontal spray pattern, and the swath is similar to a boom sprayer's. It moves through narrow places and around trees and other obstacles, which suits irregularly shaped areas.
Nozzle size, material and wear
Nozzle size depends on the desired application rate, ground speed and nozzle spacing. Keep the product's application directions at hand when you choose, and follow the manufacturer's height and spacing recommendations for the tip and angle you pick: a nozzle has to fit that whole setup, not only the flow you want.
Tips come in hardened stainless steel, stainless steel, brass, ceramic and several plastics. Hardened stainless steel and ceramic are the most wear-resistant and the most expensive. Plastic tips resist corrosion and abrasion. Brass tips wear rapidly with abrasive materials such as wettable powders and are corroded by some liquid fertilizers.
Wear raises flow: after 50 hours of spraying, a brass nozzle can have a 10 to 15 percent higher flow rate, while a hardened stainless steel nozzle rises only about 2 percent. Before calibration, check all nozzles on the boom for wear and size, and replace worn nozzles and nozzles of the wrong size.
Pressure changes the droplets and the pattern
Excessively high pressure produces small droplets susceptible to drift, and excessively low pressure produces larger, less effective droplets and poor pattern uniformity down the length of the boom. So when you change the pressure, look at the pattern again as well as the flow, and stay within the pressure range the manufacturer gives for that tip. Spray drift is a major concern above 40 psi. Extended-range flat-fan nozzles use 10 to 30 psi for soil applications and make smaller drops at 30 to 60 psi.
Sprayer tips and nozzles for a spray bar, boom extender and pasture sprayer
On a spray bar (the pipe that carries the nozzles), the sprayer tips and nozzles are chosen by the job: regular flat fan tips for broadcast herbicides, even flat fan tips for banding, cone nozzles where foliage penetration matters. A boom extender nozzle added at the end of a boom widens the swath; check that the swath it adds is uniform with the spray-water test described above. Boomless pasture sprayer nozzles are the cluster nozzles of a boomless unit, which makes a horizontal pattern with a swath similar to a boom's. A DIY boom sprayer takes its nozzles from the same table of types, sizes and tip materials, and its output is checked against the nozzle chart before it is used on a crop.
Greenhouse, double and spiral cone nozzles
Greenhouse spray nozzles that must reach leaf undersides are cone nozzles: at 40 to 80 psi they make small droplets that cover the underside of leaves better than any other nozzle type. A spiral full cone spray nozzle belongs to the full cone group and carries the same limits: very susceptible to drift and not recommended for broadcasting herbicides. On a backpack sprayer with a double nozzle, treat the two outlets as two nozzles whose combined output you measure in the calibration.
Ultra low drift spray nozzles
Ultra low drift spray nozzles are the drift-reduction nozzles described under drift guard nozzles below: a pre-orifice nozzle makes a standard flat-fan pattern at a lower exit pressure, which gives a larger droplet spectrum with fewer driftable fines.
Keep your spray records in one place. Free to start.
Body, cap, screen and tip
Most nozzles have four main parts: the body, the cap, the screen (strainer) and the tip or orifice plate. Some also have a separate spinner plate. Bodies and caps come with threads or quick-attaching adapters, and the tips are interchangeable in the cap. When a supplier quotes a replacement, ask whether the price is for the metering tip, the cap or holder, or the whole assembly, so that an invoice for a cap is not taken for the spray orifice you actually have installed.
Strainers are the best defense against nozzle plugging and pump wear. The nozzle screen should be as large as the nozzle size permits, with a screen opening smaller than the nozzle opening, and the nozzle catalog gives the screen size for each nozzle. Ask for the screen recommended for your exact product and nozzle: a finer screen is not automatically better.
Screens with a check valve prevent nozzle dripping. They are used where the sprayer is stopped and started often, such as small target areas, near sensitive crops, indoors or on right-of-way treatments, and the spring-loaded ball valves must be checked frequently. Test shutoff and dripping separately from the running spray pattern.
Wrong flow from a nozzle
Wrong flow rates come from damaged, worn or plugged nozzles or strainers, and from hose restrictions between the pressure gauge and the nozzle. Clean nozzles with a toothbrush, not a pocket knife, and never blow out a nozzle with the mouth.
When the flow changes, check these in turn: damaged or worn tips, plugged tips and strainers, and anything restricting the hose between the gauge and the nozzle. After you replace a worn tip, measure the output again and write the result down.
Calibrating a boom sprayer: check every nozzle, then time the 128th-acre course
Calibrating a boom sprayer starts with the nozzles: checking all of them for uniform flow is always the first step. Collect the water from each nozzle for one minute at constant pressure and find the average. Every nozzle should be within 10 percent either side of that average; clean or replace any nozzle outside it, then retest. In Montana State's example of five nozzles with 30, 29, 30, 24 and 30 ounces, the average is 28.6 ounces, the range is 25.74 to 31.46 ounces, and nozzle 4 has to be cleaned or replaced.
With uniform nozzles, use the 128th-acre method to find the output of the whole boom:
- Look up the course length for your nozzle spacing: 18 inches is 227 feet, 20 inches 204 feet, 30 inches 136 feet, 36 inches 113 feet and 40 inches 102 feet. For any other spacing, divide 340 by the spacing in feet.
- Drive the course at your spraying speed two or three times and average the time.
- Collect water from one nozzle at the same pressure for that time. Each ounce collected equals one gallon per acre, so 30 ounces in 30 seconds on a 204-foot course is 30 gallons per acre.
The 5940 formula is in boom sprayer selection, and the full procedure is in the calibration guide.
Sprayer drift guards and shields
Pesticide spray drift is the movement of pesticide dust or droplets through the air away from the intended application area. Nozzle type, angle and orientation, boom height and operating pressure influence the production of driftable drops. A 100-micron droplet can drift about 50 feet in a 3 mph breeze, and a 10-micron droplet about 3,000 feet.
Drift guard nozzles and anti drift spray nozzles
A drift-reduction pre-orifice nozzle makes a standard flat-fan pattern at a lower exit pressure, which gives a larger droplet spectrum with fewer driftable fines. Two styles are available: the RF Raindrops flat spray nozzle (105 to 115 degree fan angle) and the Drift Guard flat spray nozzle (80 and 110 degree angles). They replace conventional 80 and 110 degree flat-fan tips in broadcast applications at a recommended 30 to 60 psi.
Shields on the boom or nozzles
Shielding the boom or individual nozzles can reduce spray drift, and the shields must not interfere with uniform deposition of the spray on the target area (Gramoxone SL 3.0 label, section 6.4.6, Shielded Sprayers).
On a backpack or hand sprayer, a drift guard means one of the two options above: a pre-orifice low-drift nozzle, or a shield on the nozzle. Before buying a guard for a backpack, hand, Roundup- or Solo-type sprayer, ask for the exact model and its installation instructions, and check that it fits your wand and nozzle. Then confirm the spray still lands evenly on the target. For Gramoxone SL 3.0, read the Shielded Sprayers subsection together with the other drift restrictions on the label.
Hooded sprayers: two areas, calibrated separately
A hooded sprayer has several nozzles under the hood and directed (banded) nozzles outside it, and each may not cover the same area. The calibration is done for the area under the hood and for the banded nozzles outside it separately, because the two can spray different rates or chemicals. The same nozzle is used across all nozzles on the hood. Before calibrating, sketch the strips treated under the hood and by the outside band nozzles, and label which nozzle serves each strip and which supply feeds it.
Hooded sprayers are run at or under 5 mph, slower than boom sprayers. Each nozzle is caught individually, which is preferred because it shows nozzle uniformity. Keep each nozzle's own catch rather than only the total: a total can hide which nozzle needs attention.
A 28-inch hood on 36-inch rows leaves two banded nozzles covering 8 inches in total, 4 inches on each side. When one tank feeds all nozzles, the hood covers 78 percent of the width and the band 22 percent, so flow to the band nozzles is reduced in that proportion with smaller orifices or nozzles, against manufacturers' recommendations.
Drift guards in dicamba rules
For over-the-top dicamba on dicamba-tolerant crops, the downwind buffer can only be reduced if additional protections such as hooded sprayers are used. Check the conditions of your product before you count on a buffer reduction.
Next step
Write down the tip model, spacing, pressure and treated width, then measure the sprayer's output with the installed nozzles at working pressure.