Vern Hofman, Extension Agricultural Engineer
North Dakota State University
Fargo, North Dakota

INTRODUCTION

The proper application of pesticides has never been more important as chemical application continues to increase. The margin of application error has narrowed, especially with low-rate more selective pesticides. Also, emphasis on proper chemical use, reduced drift and efficacy is required by both economic and environmental concerns.

Equipment manufacturers are constantly changing and improving application equipment to produce better results. New equipment and application methods are available to keep chemicals on target and apply them at the correct rate. Misapplication and off-target application of pesticides will not be allowed.

NEW EQUIPMENT AND INNOVATIONS

Nozzles

Several new nozzles have been introduced recently by nozzle manufacturers. Those include the following:

• Extended range(XR)* or LF**
• Low Drift DG* or Raindrop*
• Turbo Floodiet*
• Turbo Teejet*

The extended range nozzles are flat fan nozzles that provide uniform coverage at pressures as low as 15 psi which will increase drop size resulting in reduced off-target application. The extended range nozzle works extremely well for pre-emergence surface applied herbicides and post-emerge herbicides. They operate over a wide pressure range up to 60 psi. This makes them ideal for sprayers with automatic rate controllers that adjust pressure to assure consistent application rates. These nozzles are excellent replacements for standard flat fan nozzles as they produce similar size drops in the 30 to 40 psi range as standard flat fan nozzles but they also produce a uniform spray pattern at low pressures down to 15 psi reducing drift potential.

The low drift spray tips use a pre-orifice design to create larger drops at the same flow rate and pressure than comparable flat fan tips. Low drift spray tips will fit in existing spray nozzle bodies without any alterations and are designed to operate at pressures of 30 to 60 psi. These nozzles offer a major reduction in driftable fines for pre-emerge surface applied herbicides and post-emerge herbicides. Use caution to be sure the pesticide used can be applied with larger drops as coverage of the plant surface will be reduced.

• Spraying Systems Co. , wheaton, IL
• Delavan-Delta, Inc. , Lexington, TN

(Use of brand names is not intended as an endorsement. It is only used to identify a product.)

The turbo floodjet nozzle produces a wide angle flat spray pattern that is produced by a pre-orifice design with a special turbulence chamber to create much larger drops and a more uniform pattern than standard flood tips. The large orifice resists plugging and is excellent for soil incorporated herbicides, pre-emerge herbicides and liquid fertilizer. They are available in stainless and plastic and are designed to operate at 10 to 40 psi.

The newest nozzle on the market is the turbo-teejet. It produces a flat fan spray pattern that is created by a pre-orifice design that creates significantly larger drops over a wider pressure range to reduce the amount of driftable fines than comparable flat fan tips. This design creates a spray pattern that is uniform when spray patterns are overlapped approximately 30%. It can be operated over a wide pressure range from 15 up to 90 psi and fits in a nozzle cap designed for a flat fan nozzle. It produces a large drop that is very resistant to drift so it is an excellent choice for drift-sensitive applications.

COLOR-CODED NOZZLES

Many applicators must change nozzles to obtain the application rate required by the chemical being applied. This may require several sets of nozzles which increases the chance of different size nozzles being mixed, as it is often very difficult to read the number stamped on the tip. Color coding solves this problem. Nozzles of the same color will all have the same orifice size. One caution, nozzles of the same color will have a different spray angle width such as 80o and 110o. Color-coded nozzles are available in plastic, stainless steel or ceramic. The stainless steel and ceramic nozzles are either ceramic or metal orifice inserts embedded in a plastic housing. Different manufacturers use different color codes. Be sure all nozzles are from the same manufacturer to avoid mistakes.

QUICK-CHANGE NOZZLES

Quick disconnect caps have replaced the threaded nozzle caps. Nozzles are much faster to clean or change as only a one-fourth turn of the cap is needed to remove it. Caps are also color coded so if standard brass or stainless steel nozzles are used, they can be installed in the color caps similar to the method used with color-coded nozzles.

When flat fan nozzles are used, caps with flat nozzle openings are available that will automatically orient the nozzle in the proper plane when installed on the spray boom.

MULTIPLE NOZZLE BODIES

Multiple nozzle bodies are extremely handy for a quick change of nozzles on a sprayer. They are available with either 2, 3, 4, or 5 nozzle openings so a quick change of spray nozzles can be done. They include a diaphragm check valve and quick disconnect nozzle caps.

INJECTOR SYSTEMS

Injectors measure and introduce concentrated chemical into the spraying system at the time of application. They keep the chemical separate from the water, helping eliminate a large amount of mixed spray at the end of the day or season. These units contain speed monitors and automatically change the application rate to adjust for a change in travel speed. Pumps for metering chemical are usually positive displacement type such as a piston or peristaltic. It is extremely important to keep these units in excellent condition such as replacing the metering tubes in peristattic pumps yearly. If a small metering error occurs, the application error may be multiplied which will mean over or under application from the intended rate. They must be calibrated occasionally to be sure the correct amount of chemical is being applied on each acre.

SPRAY CONTROLLERS

Spray controllers automatically adjust the flow rate of the sprayer to keep the GPA unchanged if a change in speed occurs. They contain a speed sensor such as a radar gun or use a non-driven wheel revolution counter. The radar sensor is the most accurate but is the more expensive. The change in flow rate is accomplished by increasing or decreasing system pressure. The newer low pressure or extended range flat fan nozzles work well with controllers.

SPRAY MONITORS

Monitors measure the amount of spray that is being applied per acre. They have a flow meter and speed sensor built into the system which is used to determine the application rate in gallons per acre. Flow rate and area covered are continuously calculated and shown to the operator on a display module. They will tell the applicator how much spray is being applied on each acre but they do not automatically adjust application rate.

SHIELDED SPRAY BOOM

Spray drift is becoming more of a problem due to wind and other atmospheric conditions. In the Great Plains, strong winds occur almost daily during the majority of the daylight hours. Usually the only time when wind velocity is low enough for spraying is during the early morning or late evening hours. This considerably limits the hours available for spraying.

Shielded sprayers are a way to control wind in a limited area. The shield creates a low wind atmosphere so the hours available for chemical application can be extended. Several spray drift studies have found that drift from a shielded sprayer in a 20 mph wind was about equal to the drift from an unshielded sprayer in a 10 mph breeze.

AIR-ASSIST SPRAYERS

Air-assist sprayers direct spray drops into the plant canopy with a blast of air. The air tends to stir up the plant canopy exposing more plant surface to the application. Some Systems use a curtain of air blasted down next to the spray nozzles which help carry the drops into the plant canopy. Others create drops within the air stream from an airfoil. It should be noted that air-assist technology is only suited for post-emerge applications. Studies show that spray drift is higher on air-assist sprayers when the soil is almost bare as compared to conventional systems. The air blast bounces off the ground and carries the small drops up into the atmosphere.

Preliminary studies show that with post emergent pesticides, mid canopy coverage with air-assist is better than with conventional sprayers. These tests were completed with 3 brands of sprayers. Other studies conducted on dry beans for controlling white mold, the air-assist sprayer and a high pressure directed spray (175 psi) application were equal in performance and significantly better than a conventional low pressure (30 to 40 psi) spray application.

WHEEL CARRIED BOOMS

Proper boom height for chemical application depends on the nozzle used but should be maintained at the proper height. Bouncing booms, which often occurs on rough terrain, may cause poor chemical application. Booms carried on wheels will help maintain proper nozzle height. But, booms must be built stronger to withstand added stress when the wheels sink into soft soil or mud and they should contain shock absorbing equipment to eliminate boom chatter when running on rough ground.

Some manufacturers have built booms with self-leveling suspension systems. They help considerably in maintaining the boom parallel with the soil surface. Also, slowing travel speed helps reduce boom bounce.

AERIAL PATTERN TESTING

Up until the last few years, the only means available for fast determination of spray patterns of aircraft was to visually estimate the pattern from dye sprayed on sheets of paper spread across the spray swath. About 15 years ago, a wet chemistry process was developed using copper-sulfate with a copper tracer. This was labor intensive, produced reasonably fast results, and was much more accurate than a visual analysis. Then, a method was developed which utilized a fluorescent dye sprayed on a long strip of paper. The dye deposited on the paper tape was analyzed with a fluorometer interfaced with a computer to collect the data. The latest development involves the use of a cotton string in place of the paper tape. It is much easier to spread out across a swatch width and it is a more efficient collector as compared to a paper tape. The string allows dye to collect on all sides as compared to only one flat surface with the paper tape. The dye deposited on the string is read with a fluorometer interfaced with a computer to collect the data. The data is analyzed with the computer and the spray pattern graph is produced with a laser printer.

GROUND SPRAYER TESTS

Pattern tests on ground sprayers are usually done with the use of a corrugated tray collecting spray from a section of the spray boom which is poured into tubes. High or low discharges will show up in the tubes which indicates a problem. This test method will indicate worn nozzles, pressure differences, improper nozzle spacing and improper boom height. This test will not give an indication of flow rate or the application in GPA which must be done by calibration.

CLOSED CHEMICAL HANDLING SYSTEM

Worker protection is becoming more important, especially in the area of pesticide handling. Workers face considerable hazards when handling concentrated pesticides and handling pesticides with pumps. Measuring pesticides with meters or volume measuring equipment is going to become more common.

UNUSED CHEMICAL DISPOSAL

Pesticides used in agriculture must be handled safely to protect the applicator, family and consumer. Storage of pesticides, disposal of old or unused pesticide and rinsing of empty containers are becoming major concerns as potential sources of groundwater and environmental pollution.

Facilities for catching, holding and disposing of pesticide rinsate are being built. The type and size of the facility needed by commercial or farm applicators may vary depending on the amount of pesticide used and the amount of wash water needed. Considerable design information is available in a book produced by Midwest Plan Service. It is titled ÏDesigning Facilities for Pesticide and Fertilizer Containment," manual #MWPS-37. It is available from county Extension offices in North Dakota.