Winter Meeting and Sprayer "Tips"  02/06/18 10:58:54 AM

 
Spraying Tips--Much has been written/reviewing regarding this topic over the years. It again seems to be a timely topic for additional reasons—RR2Xtend Soybeans. Many herbicide labels are now recommending specific tips/nozzles for their products to comply with EPA requirements. There is a contingent of tank mixes with Roundup Ready applications in which off-target drift is becoming a concern yet again.  (RR2Xtend)  Prior to 1996, we worried about off-target drift with every treatment that was applied—some treatments more than others (growth regulated and auxin treatments—2,4-D/Banvel).  Roundup Ready applications lessened that concern as volatilized (vapor) movement of the treatment wasn’t a large concern.   Now, we are in the midst of tank-mix partners being widely added to the Roundup treatment and the increase of RR2Xtend acres,  we re-vert back to some of the pre 1996 concerns regarding herbicide drift.’
SO here is our somewhat simplified review 
Spray-droplet diameters are measured in micrometers. A micrometer is approximately 1/25,000 of an inch and is usually referred to as a “micron.” For reference, the thickness of a human hair is approximately 100 microns. Drops smaller than 150 microns in diameter (smaller than the diameter of a sewing thread) usually pose the most serious drift hazard. Drift is far less likely to be a problem when droplets are 200 microns and larger in size. A study indicated that spray particles less than 50 microns in diameter remain suspended in the air indefinitely or until they evaporate. This should be avoided because there is no way to control deposition of very small droplets.
A classification system developed by the British Crop Protection Council (BCPC) and the American Society of Agricultural and Biological Engineers (ASABE) assigns a droplet-size category to a nozzle based on droplet-size spectrum (Table 1). This system allows for comparison of droplet size between various nozzles, operating conditions (pressure), and manufacturers.
Table 1. Droplet-size classification chart.
Droplet Category1 Symbol Approximate VMD Range2 (microns)
Very Fine VF < 145
Fine F 145-225
Medium M 226-325
Coarse C 326-400
Very Course VC 401-500
Extremely Course XC > 500
1 ASABE (American Society of Agricultural & Biological Engineers) Standard 572.
2 VMD = Volume median diameter—a value where 50% of the total volume or mass of liquid sprayed is made up of droplets larger than this value, and 50% is made up of droplets smaller than this value. Reported VMD ranges vary widely, based on the type of laser analyzer used.
Spray Drift--There are two kinds of drift:
  • Particle drift is off-target movement of the spray particles.
  • Vapor drift is the volatilization of the pesticide modules and their movement off target.
A Mississippi State University study analyzed data from more than 100 studies involving drift from ground sprayers. Of the 16 variables considered, three were most important.

Spray when the wind speed is 10 mph wind or less.
  1. Wind Speed. I realize that there are not many days in the application season when sustained winds are below 10 mph.   This is far more of a issue with post-emergence applications than with pre-emergence.  Keep in mind that when wind speed was doubles, there is almost a 700% increase in drift when the readings were taken 90 feet downwind from the sprayer.   
  2. Boom Height. When the boom height was increased from 18 to 36 inches, the amount of drift increased 350% at 90 feet downwind.
  3. Distance Downwind. If the distance downwind is doubled, the amount of drift decreases five-fold. Therefore, if the distance downwind goes from 100 to 200 feet, you have only 20% as much drift at 200 feet as at 100 feet and if the distance goes to 400 feet, you only have 4% of the drift you had at 100 feet.  Check wind direction and speed when starting to spray a field.
    • Start spraying one side of the field when the wind is lower. Spray only part of the field because of wind speed, wind direction, and distance to susceptible vegetation. The rest of the field can be sprayed when conditions change.
Spray Pressure and Sprayer Speed--Pesticide drift also can be reduced by using one of the new types of tips and by adjusting spray pressure. Higher spray pressures produce smaller droplets which are more susceptible to drift. If using a rate controller, be careful of increased speed. Since most rate controllers increase the pressure to maintain the same gpa when the speed increases, try to maintain the speed within 10%. For example, if you're applying 20 gpa at 8 mph at 40 psi and you increase the speed to 11 mph, the pressure will be 75.5 psi which will produce small particles prone to drift. Also, this pressure will be above the operating range of most tips. Drift reduction agents may be helpful.
New spraying technology such as the "blended pulse" can decrease the risk of drift by allowing flow rate to be controlled independently of spray pressure.
Nozzle Tip Selection--It is important to select the nozzle tip and pressure that delivers the spray particle size needed to give good efficacy with the pesticide. Always consult the pesticide label for information on application. This may include carrier rates, nozzle types, spray particle size, pressure, drift, additives, etc.  Our preference is a GreenLeaf  medium pressure TurboDrop XL Venturi nozzle which delivers excellent drift control along with excellent coverage for most all of our post-emergence ground applications.
Table 1. Distances spray droplets travel with various wind speeds from 3-foot boom height.
Droplet Size Wind Speed
(microns) 5 mph 10 mph 15 mph 20 mph
  Distance traveled in feet
100 24 48 72 96
200 9 18 26 35
400 5 9 14 18
500 4 7 10 14
600 3 6 9 12
Droplet Size. All nozzle tips produce a range of droplet sizes with low-drift nozzles reducing the number of small droplets (fines). Droplets less than 150 to 200 microns are most susceptible to spray particle drift. Nozzle tips come in several sizes within a given type of nozzle. Smaller nozzles designed to give a lower output will also produce a higher percentage of small droplets compared to larger tips.If the air-induction spray nozzle tips produce the spray particle size needed for the pesticide and application method being used, they may be the best choice. Most of the standard air-induction spray tips give the best performance when used at about 70 psi. Check with the manufacturer to get their recommendations. Extended range air-induction tips are best used at around 40 psi. Again, check with the manufacturer for their recommendation.
You can manage spray drift damage.
  1. Recognize and adjust for the factors that affect it:
    • wind speed (spray when it's less than 10 mph)
    • nozzle height
    • spray nozzle tip
    • pesticide selection
    • spray additive used
  2. Keep spray a safe distance from susceptible vegetation.
 
Courtesy of
Robert Klein
Extension Western Nebraska Crops Specialist

 
Recommended sprayer nozzle tips, pressures, and speeds to achieve various droplet sizes.    
For Coarse Spray Quality 10 GPA  
           
  Nozzle Spacing  
Speed mph Rate
gpm
20-inch Rate
gpm
30-inch  
6 0.202 TT110025 @ 26 psi 0.303 AIXR110025 @ 59 psi  
7 0.236 TT11003 @ 25 psi* 0.354 AIXR11003 @ 56 psi*
or TT11004 @ 31 psi*
 
8 0.269 TT11003 @ 32 psi 0.404 TT11004 @ 41 psi  
10 0.337 AIXR11003 @ 50 psi*
or TT11004 @ 28 psi*
0.505 TT11005 @ 41 psi*  
12 0.404 AIXR11003 @ 72 psi
or TT11004 @ 41 psi
0.606 XRC11008VK @ 23 psi
or TT11005 @ 59 psi
 
14 0.471 TT11004 @ 55 psi 0.707 XRC11008VK @ 31 psi
or TT11006 @ 55 psi
 
 
*Just into coarse droplet size
 
For Medium Spray Quality 10 GPA  
 
  Nozzle Spacing  
Speed mph Rate
gpm
20-inch Rate
gpm
30-inch  
6 0.202 TT11002 @ 41 psi 0.303 TT110025 @ 59 psi  
7 0.236 TT110025 @ 36 psi*
or TT11002 @ 56 psi
0.354 TT11003 @ 56 psi* or XRC11004VK @ 31 psi  
8 0.269 TT110025 @ 46 psi 0.404 TT11003 @ 73 psi
or XRC11005VK @ 26 psi
 
10 0.337 TT11003 @ 50 psi*
or XRC11004VK @ 28 psi
0.505 XRC11005VK @ 41 psi
or XRC11006VK @ 28 psi*
 
12 0.404 XRC11005VK @ 26 psi 0.606 XRC11006VK @ 41 psi  
14 0.471 XRC11005VK @ 35 psi 0.707 XRC11006VK @ 55 psi  
 
*Just into medium droplet size
 
For Coarse Spray Quality 20 GPA  
 
  Nozzle Spacing  
Speed mph Rate
gpm
20-inch Rate
gpm
15-inch  
6 0.404 AIXR11003 @ 72 psi
or TT11004 @ 41 psi
0.303 AIXR110025 @ 59 psi  
7 0.471 TT11004 @ 55 psi 0.354 AIXR11003 X 56 psi*
or TT11004 @ 31 psi*
 
8 0.538 TT11005 @ 46 psi* 0.404 TT11004 @ 41 psi  
10 0.674 TT11006 @ 50 psi*
or XRC11008VK @ 28 psi
0.505 TT11005 @ 41 psi*  
12 0.808 XRC11008VK @ 41 psi*
or TT11006 @ 72 psi
0.606 XRC11008VK @ 23 psi
or TT11005 @ 59 psi
 
14 0.942 XRC11010VK @ 35 psi 0.707 XRC11008VK @ 31 psi
or TT11006 @ 55 psi
 
 
*Just into coarse droplet size
 
For Medium Spray Quality 20 GPA  
 
  Nozzle Spacing  
Speed mph Rate
gpm
20-inch Rate
gpm
15-inch  
6 0.404 XRC11005VK @ 26 psi 0.303 TT110025 @ 59 psi  
7 0.471 XRC11005VK @ 35 psi 0.354 TT11003 @ 56 psi*
or XRC11004VK @ 31 psi
 
8 0.538 TT11004 @ 72 psi
or XRC11006VK @ 32 psi
0.404 TT11003 @ 73 psi
or XRC11005VK @ 26 psi
 
10 0.674 XRC11006VK @ 50 psi 0.505 XRC11005VK @ 41 psi
or XRC11006VK @ 28 psi*
 
12 0.808 XRC11008VK @ 41 psi 0.606 XRC11006VK @ 41 psi  
14 0.942 XRC11008VK @ 55 psi 0.707 XRC11006VK @ 51 psi  
 
 
*Just into medium droplet size
 
For Glyphosate at 10 GPA  
 
  Nozzle Spacing  
Speed mph Rate
gpm
20-inch Rate
gpm
30-inch  
6 0.202 AIXR110002 @ 41 psi 0.303 AIXR11003 @ 41 psi  
7 0.236 AIXR110025 @ 36 psi 0.354 AIXR11003 @ 56 psi
or AIXR11004 @ 31 psi
 
8 0.269 AIXR11003 @ 32 psi or AIXR110025 @ 46 psi 0.404 AIXR11004 @ 41 psi  
10 0.337 AIXR11003 @ 50 psi
or AIXR11004 @ 28 psi
0.505 AIXR11005 @ 41 psi  
12 0.404 AIXR11004 @ 41 psi 0.606 AIXR11006 @ 41 psi  
          14 0.471 AIXR11004 @ 56 psi
or AIXR11005 @ 36 psi

 
 
 
 
0.707 AIXR11006 @ 55 psi  
 
For 15 and 20 GPA Fungicide and/or Insecticide
This is a general recommendation. See product label.
 
 
  Nozzle Spacing  
Speed mph Rate
gpm/gpa
20-inch Rate
gpm/gpa
30-inch  
6 0.303/
15
XRC11003VK @ 41 psi 0.455/
15
XRC11004VK @ 52 psi  
7 0.354/
15
XRC11004VK @ 31 psi 0.530/
15
XRC11005VK @ 45 psi  
8 0.404/
15
XRC11004VK @ 41 psi 0.606/
15
XRC11006VK @ 41 psi  
10 0.674/
20
XRC11006VK @ 50 psi 0.505/
20
15-inch Spacing
XRC11005VK @ 41 psi
 
12 0.808/
20
TJ60-11008 @ 41 psi 0.606/
20
15-inch Spacing
XRC11006VK @ 41 psi
 
14 0.943/
20
TJ60-11008 @ 56 psi 0.707/
20
15-inch Spacing
XRC11006VK @ 55 psi
 
             
 
John W. McNamara
Agronomist
Wiles Bros. Inc.
606 Wiles Road
Plattsmouth NE. 68048
(402) 298-8550--Office
(402) 499-3870--Cell
(402) 298-7174--Fax
 
 
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