The goal of any spray application should be to achieve the intended result, whether it be eliminating targeted weeds, disease, insects, or desiccating the crop.

Weeds or insects that compete with or stress the crop reduce the yield. Effective spray application eliminates the pests so the maximum crop yield can be achieved.

Crop damage can result in several ways:

• If the spray application is not effective, the insects or disease can damage the crop.
• When the wrong chemical or incorrect application rate is used the crop can be stressed or damaged.
• Spray drift onto adjacent fields can also result in unintended chemical application and damage.

An effective application ensures that chemical costs are minimized and re-spraying (and additional cost) is not required.

Selecting the chemical, or combination of chemicals, that will achieve the desired result is vital to maximizing the application result and minimizing the cost. Use of multiple chemicals (e.g. tank mixing) can reduce application costs by letting you apply several chemicals in a single application. However, chemical compatibility must be considered.

Information on chemical selection is available from chemical companies, chemical suppliers, crop guides, agriculture extension divisions and agricultural consultants.

Determining the correct application rate for both the chemical and the water is important. You must select the correct amount of chemical for the application as well as the appropriate amount of water for the volume of chemical used.

An additional consideration that will affect application rate is droplet size. Typically, the larger the desired droplet size, the higher the required application rate. Please refer to the Droplet Size section for more information.

Information on application rates is available from chemical companies, chemical suppliers, crop guides, agriculture extension divisions and agricultural consultants.

• Apply the chemical at the growth stage of the target recommended by the chemical manufacturer.
• Apply the chemical under the best climatic conditions possible – if the target is stressed from heat, cold or drought the chemical may not perform optimally.

• Auto-rate vs. Pressure Controlled Spray Systems
  • Auto-rate equipped sprayers monitor the sprayer speed and liquid flow to the spray booms and automatically adjust the flow or pressure to compensate for changes in sprayer speed. When selecting a spray tip you need to consider the range of speeds at which the sprayer will operate and ensure that the spray tip can accommodate.
  
  
  • An additional consideration is that: as the sprayer speeds up, the system pressure increases and the droplet size decreases and; as the sprayer slows down, the system pressure decreases and the droplet size increases.
  
  
  • Spray systems that utilize a constant pressure setting (except Blended Pulse Width systems – see below) to determine the application rate apply a constant amount of spray volume (gallons or liters per minute), regardless of changes in sprayer speed. When spraying at a slower speed, the application rate will be higher than the intended rate. When spraying at a higher speed, the application rate will be lower than the intended rate.
    
    
• Blended Pulse Width Spray Systems
  • Sprayers equipped with Blended Pulse Width systems (AIM Command or Sharp shooter) utilize a solenoid valve on the nozzle body which turns the spray on or off many times a second. This allows you to:
    • Get a much larger speed and application rate range for a given size spray tip.
    • Spray at a constant pressure while changing speed which allows you to maintain a constant droplet size.
• Pressure Capability
  • Note the maximum operating pressure of your sprayer and select a spray tip with a suitable operating range.
• Pump Output Capability
  • If you want to apply a high volume of liquid (high application rate), check that the total flow from all the nozzles at the highest sprayer speed does not exceed the pump output capacity of the sprayer.

• Individual droplets are measured in microns (a human hair is approximately 100 microns in diameter).
• The spray from a nozzle is made up of a wide range of droplet sizes and is measured as VMD (Volume Median Diameter).
• The VMD means that half of the total spray volume consists of droplets larger than the VMD and the other half of the total spray volume consists of droplets smaller than the VMD. A large percentage of the droplets are near the VMD.
• The larger the micron or VMD number, the larger the droplet size.
• Droplets smaller than 200 microns are more susceptible to drift and droplets larger than 600 microns may not deposit effectively.

In an effort to make droplet size easier to understand and work with, the American Society of Agricultural Engineers (ASAE) established standard categories and colors for droplet size ranges. Please note that the classification category color codes do not correspond to Tip-Cap colors

Choosing the best droplet size for your spray application is often a trade-off between coverage and drift control.

• Smaller droplets = better coverage
  • More droplets in same volume of water
  • Smaller droplets deposit (“stick”) on the target better and are less likely to roll off
  • More likely to drift
• Larger droplets = better drift control
  • Fewer droplets in same volume of water
  • Larger droplets don’t deposit (“stick”) on the target as well and may roll off
  • Less likely to drift

Droplet Size – Size vs. Quantity

The total volume of spray on both leaves shown on the right is the same. Only the droplet size is different. Note - In an actual spray application there would be a range of droplet sizes produced by the nozzle.

Droplet Size - Coverage vs. Drift Control

Some chemicals are more effective when applied with a certain droplet size / VMD spray, while others are just as effective when applied with larger droplets.

Within chemical groups, contact products (Mode of Action groups 6, 10, 22) usually benefit more from greater volume than from smaller droplets. Systemic products (Groups 2, 4, 9) are more flexible. Group 1 is systemic, but not as much as others, and it also targets grassy weeds, so finer sprays are better. Mode of Action tables are available from crop guides, agriculture extension divisions and agricultural consultants. The recommended VMD / droplet size information may be shown on the product label or is available from the chemical manufacturer.

The chart below is a general guide for the droplet size range that is effective for the various applications.

Please note that the classification category color codes do not correspond to Tip-Cap colors.

If you are tank mixing to spray both grassy and broadleaf weeds, this creates a challenge with single spray tip application systems because you can only spray one VMD (droplet size). While all spray tips produce a range of droplet sizes, which offsets this problem somewhat, the largest percentage of the droplets produced will be in a certain droplet size range and will only be most effective on one category of weed.

Multi-tip application systems (COMBO-RATE ®) provide a solution to this problem because they allow you to spray with more than one spray tip (and droplet size) at a time.

• Drift Factors and Considerations
  • Wind speed is the greatest drift factor.
  • Spray nozzles - for a given size of spray nozzle and pressure:
    • A nozzle with a larger orifice produces larger droplets than one with a smaller orifice. Most nozzles produce smaller droplets / VMD at higher pressures.
    • A 110 degree nozzle has a smaller VMD than an 80 degree nozzle (for the same size of nozzle, operating at the same pressure).
    • Drift control nozzles produce larger droplets.
    • The closer the nozzle is to the ground, the less susceptible the spray is to drift.
  • Droplet size
    • Small droplets drift more easily than large droplets.
    • At higher temperatures, when humidity is low, small droplets may drift due to air inversion
  • On auto-rate controller equipped sprayers, the VMD decreases when you speed up and increases when you slow down, due to the flow rate / pressure change required to compensate for the change in speed.
  • The spray is moving at the same speed and direction as the sprayer when it exits the spray nozzle.
    
    
• Common Drift Control Nozzle Types

  • Closed chamber - Utilize a pre-orifice and exit orifice on either side of a uniquely shaped “closed chamber” where the droplets are formed (e.g. COMBO-JET ®).

  • Air Induction - Utilize a small “port” on the nozzle that allows air to mix with the spray to form the droplets.
  • Variable rate – Utilize a needle and seat to vary the rate in response to changes in the spray system pressure. Different nozzles produce a different droplet size range.
    
    
• How to Minimize Spray Drift
  • Spray at the highest recommended application rate (water volume).
  • Spray at the lowest recommended nozzle pressure.
  • Use the largest size nozzle that gives the required flow.
  • Use a drift reduction nozzle model.
  • Spray at the lowest height recommended for the nozzles being used.
  • When near adjacent fields, slow down and reduce the pressure (an auto-rate control automatically reduces the pressure as the speed reduces).

• While the information provided in Tipnology can be applied to many types of spray application, it is most specifically intended to apply to broadcast spray application. Broadcast spray application is where the complete field is sprayed (as opposed to row crop).
• For broadcast spray applications, spray tips which produce either an 80 or 110 degree flat fan pattern are the most widely used.

• Carefully read the chemical label and / or other information to determine the recommended application rate and droplet size.
• Note the application units (US gallons, Imperial gallons, Liters, etc.).
• Determine if you have a standard or blended pulse width (BPW) spray system.
• Note your nozzle spacing.
• Note your nozzle degree (80 or 110).
• What type of spray nozzle mounting do your nozzle bodies utilize – Radialock (COMBO-JET ®) or conventional - square lug (Tee Jet & Hypro)?
• Consider the pressure and flow output capability of the sprayer.
• Consider the spray application wind conditions.
• To maximize coverage and drift control, select a nozzle that will produce the largest VMD recommended for the product being applied.
• A lower pressure will produce a larger VMD / droplet size for a given spray nozzle.
• An operating pressure near the middle of the nozzle’s range will give the best pattern and allow for pressure adjustment to accommodate speed variations.
  • If the pressure is too low the edges of the pattern will start to collapse, resulting in poor overlap.
  • If the pressure is too high the nozzle will produce finer droplets at the edges of the pattern than the center, which may result in increased drift.
• An auto-rate controller will increase or decrease the pressure to compensate for changes in speed. The nozzle operating pressure range needs to accommodate the sprayer speed range.
• If you are spraying with two spray tips per nozzle body location, determine how the flow to each tip is controlled (standard vs. blended pulse spray system) and use the appropriate Tip-Cap selection procedure

• TIP WIZARD computerized nozzle selector The TIP WIZARD is a web based computerized nozzle selector that greatly simplifies nozzle selection. Just enter the desired spray application requirements and the nozzles that fit the requirements are identified. Access from your PC or cell phone at www.tipwizard.net or a Wilger CD.
• COMBO-JET ® Tip-Cap selector - standard spray systems A chart based nozzle selector that can be found in Wilger’s Tip-Cap product literature, or downloaded from www.wilger.net or a Wilger CD.
• COMBO-JET ® Tip-Cap selector – AIM Command systems A chart based nozzle selector that can be downloaded from www.wilger.net or from a Wilger CD.

Access TIP WIZARD from your PC or cell phone at www.tipwizard.net. Also available on WILGER’s web site CD. Select the application units you are using. Select the spray system you are using. Enter the spray application information. Click the “Search for spray tips” button. Select the best nozzle from the choices presented.

• Locate the SPRAY APPLICATION NOZZLE PERFORMANCE / SELECTOR CHARTS > COMBO-JET Tip-Caps Printable Charts (with applicable units) on the web site or CD or in the COMBO-JET Tip-Cap product literature.
  • (USGPA)
  • (IMPGPA)
• Locate the desired average sprayer speed and follow the column down to the first Tip-Cap with the required application rate.
• Follow the line with the desired application rate over to the right and note the Tip-Cap with the most desirable droplet characteristics.
• Repeat process for other Tip-Caps that match the required application rate. Select the Tip-Cap that gives the most desirable droplet size over the speed range that you will be spraying.

• Locate the SPRAY APPLICATION NOZZLE PERFORMANCE / SELECTOR CHARTS > AIM Command Tip-Cap Selector - US Gal on the web site or CD.
• Follow the instructions at the top of the selector chart.

• Worn or blocked nozzles don't apply the correct rate, or don't apply the spray evenly.
• Rate controllers ensure that the correct total amount of flow is supplied to the number of boom sections turned on. However, this does not ensure that the individual nozzles are applying the correct rate or applying the spray evenly.
• You can have worn or blocked nozzles and the rate controller will compensate by increasing or decreasing the flow so that the total flow to the boom sections remains correct.

QUICK CALIBRATOR TM Automated spray calibration instrument – just hold under an operating spray nozzle for a short while and the flow rate and application rate will be displayed.

or Graduated container Calculator Stop watch or wrist watch with second hand

QUICK CONTROL TM Easy to use hand-held Remote lets you control up to 7 individual boom sections. Easy to install on sprayer - just unplug boom control valve connectors and plug in the QUICK CONTROL Control Module.

Step 1- Check your speed - speedometers can give erroneous readings due to wheel slippage and/or variances in tire size. To verify the speed, follow the instructions in your sprayer or rate controller manual, use your GPS system to verify or:

1. Make sure sprayer is tank is half full of liquid.
2. Place 2 markers 300 feet or 100 meters apart on a section of a field that is representative of spray application driving conditions. Make sure there is enough distance to bring the sprayer up to speed before the first marker.
3. Bring the sprayer up to average sprayer speed and when you pass the first marker start timing.
4. When you pass the second marker stop timing.
5. Calculate your actual speed using the applicable formula below.

QUICK CALIBRATOR TM Turn on sprayer in test mode. Place QUICK CALIBRATOR under an operating spray nozzle. After a short time, the flow rate and application rate will be displayed. Press the arrows to increase or decrease speed and see effect on application rate. Nozzle Comparator feature allows individual flow rates to be saved, and compared against the average flow rate of all the nozzles, to check nozzle wear

Using a jug, stopwatch and calculator: Turn on sprayer in test mode. Collect the output from a nozzle in a graduated container and measure the time it takes. (Note – the larger the amount of spray collected / the more time taken, the more accurate your measurement will be). Do this for 3 or 4 additional nozzles randomly along the boom. Determine the flow rate from each of the nozzles using one of the applicable formulas below.

• If all the nozzles checked are higher or lower than the intended flow or application rate, your spray system needs to be adjusted.
• If individual nozzles vary by more than 5% from the intended flow or application rate, they need to be cleaned or replaced.