| Airborne Spray Drift Results
The Alberta Farm Machinery Research Centre (AFMRC) and Regina Research Station of Agriculture and Agri-Food Canada conducted field trials in 1994 to 1997 to measure airborne spray drift from Flexi-coil’s windscreen, Bourgault’s Clearview air curtain and the Kaletsch rotary fans. The sprayers were tested with the extended range, 80°, 015 nozzles, i.e., XR80015 and ER80-015. In addition, drift was measured from a high clearance sprayer equipped with XR, TT and DG TeeJet nozzles. An air-assist system that mounted on the high clearance sprayer was also tested. Melroe Company from Bismarck, ND donated a Spra-Coupe Model 3630 for the high clearance trials. John Brooks (Spraying Systems’ dealer) supplied the nozzles. Spencer Hilton, a Strathmore area farmer, lent AFMRC his Spra-Coupe Model 3640 to test the effectiveness of Melroe’s recently introduced energized spray process (ESP).
Flexi-coil Windscreen
Effect of Windscreen in Chemfallow Conditions
The XR, TT and DG nozzle types stand for extended range, wide angle turbo TeeJet and drift guard flat fan nozzles, respectively. The wide angle turbo TeeJet nozzles were introduced in the spring of 1995. The extended range nozzles have been used for several years. Small spray droplets, good coverage at low pressures and heights, and compatibility with automatic rate controllers made the extended range nozzles popular among applicators. However, some inexperienced applicators ignored fundamental spraying practices that resulted in increased amounts of spray drift using extended range nozzles. Recent spray drift lawsuits and complaints by neighboring farmers have increased, prompting the spray drift trials.
| The sprayers and nozzles tested by the Alberta Farm Machinery Research Centre (AFMRC) were configured as described by the manufacturer at the time of testing. The manufacturer may have built different forms of the sprayers or used different set-ups before or after AFMRC tests. When using this report, be sure to first check the sprayer being purchased or nozzle set-up is the same as used in the test. The AFMRC will help you decide how your sprayer or nozzle will perform compared with the one tested. |
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Flexi-coil and Bourgault sprayers were operated at 12 km/h, giving an application rate of 50 L/ha. The extended range nozzles were set 450 mm above the crop. The high clearance sprayer was operated at 30 km/h, giving an application rate of 30 L/ha. Nozzle height was set at 600 mm. Because booms are unsupported on most high clearance sprayers, nozzle height was set higher compared to conventional sprayers. Nozzle pressure was 275kPa in all trials. All sprayers were operated with the wind perpendicular (crosswind) to the sprayed swath (ASAE S387, “Test Procedure used for Measuring Deposits and Airborne Spray from Ground Swath Sprayers”).
Bourgault Clearview Air Curtain
Effect of Bourgault Clearview Curtain in Cereal Crop Conditions
All graphs in the report show the amount of airborne spray drift as a percent of the chemical sprayed. The first two graphs show the effectiveness of the windscreen and air curtain, respectively. Flexi-coil’s windscreen reduced airborne spray drift by 80% in 30 km/h crosswinds. For example, spray drift was 10% without the windscreen and 2% with the windscreen on. Bourgault’s Clearview air curtain reduced airborne spray drift by 50% in 30 km/h crosswinds. Spray drift was 12% without the Clearview air curtain and 6% with the air curtain on the Bourgault sprayer.
Melroe ESP Contact Charging System
Airborne Drift at High Speeds and Nozzle Height
In 20 km/h crosswinds, airborne spray drift was 15, 8 and 8% from XR11002, DG11002 and TT11002 nozzles, respectively. Spray drift from the extended range XR11002 nozzles was highest. This was expected since XR nozzles produce a higher percentage of spray droplets below 100 µm than DG or TT nozzles at 275 kPa spraying pressure. Drift was similar for DG11002 and TT11002 nozzles. The TT nozzles, like the XR nozzles, have very good coverage at low pressures, rates and spray heights (see Addendum). Therefore, the TT nozzles would work best in windy spraying conditions for the applicators using automatic rate controllers and sprayers with unsupported booms that frequently strike the ground.
Melroe introduced the Energized Spray Process (ESP contact charging system) in Western Canada in 1997 to enhance spray coverage and reduce spray drift. For the drift tests, the sprayer was fitted with XR11002 tips and operated at 360 mm above the 250 mm high cereal crop. At 23 km/h and 760 mm nozzle spacing, the application rate was 30 L/ha. The ESP system reduced drift from 13.5 to 6% in a 20 km/h wind, a reduction of over 50%.
An air-assist system was installed on the high clearance sprayer to decide the air system’s potential as a drift reduction system on high speed, high clearance sprayers. As shown in the results (graph and table), the air system increased spray drift by 5%. Spray drift increased from 15 to 20% in a 20 km/h crosswind. Applicators using air-assist systems strictly for controlling spray drift are cautioned.
Kaletsch Rotary Fans
Effect of Kaletsch Rotary Fans
Another air-assist spraying system, Kaletsch rotary fans was installed on a Bourgault Model 540 conventional sprayer. In a 20 km/h crosswind, the rotary fans reduced drift approximately 10%. The moderate downward draft created by the rotary fans did not have an adverse affect as some high speed air-assist system tested in the past.
Airborne spray drift from standard 8002 flat fan nozzles is shown for a reference point. Drift from standard 8002 nozzles applying 100 L/ha at 8 km/h was only 3% in 20 km/h crosswinds. Spraying at 100 L/ha was introduced 30 years ago as a way to reduce drift. Have the new spraying technologies come close to that level? Should they? Obviously more research is needed to answer these questions.
With the introduction of Turbo TeeJet and air induction nozzles, it seems the industry has some full circle. Back to spraying with course droplets. Air induction nozzles (Greenleaf Technologies Turbo Drop) were tested in AFMRC’s windtunnel and showed airborne drift was reduced significantly.
Airborne Spray Drift Results in 20 km/h Crosswind
Effect of Reducing Spray Pressure and Height using Extended Range110° Tips
When the wind comes up, custom applicators using extended range nozzles, especially 110° nozzles, should reduce spraying speed. When equipped with automatic rate controllers, speed should be reduced until nozzle pressure falls below 150 kPa. As shown, spray drift reduces to acceptable levels at low nozzle pressures and heights. However, reducing spraying speed reduces work rates. At $3.50 to $4.00 per acre, some operators find reducing spraying speed difficult to do.
Producers should be aware custom applicators can reduce spray drift. From tests conducted, results show airborne spray drift from wide angled nozzles used in high speed spraying (a worst case scenario) and standard nozzles used in conventional spraying (a best case scenario). From the two scenarios, applicators can select a spraying speed and nozzles to keep spray drift at acceptable levels.
Sprayer Operating Conditions and Airborne Spray Drift Results (% of chemical rate)
Sprayer Type | Nozzles | Spray Height
(mm) | Spray Rate
(L/ha) | Spraying Speed
(km/h) | Wind Speed
(km/h) |
10 | 20 | 30 | 40 |
| Conventional | DG11002 | 450 | 100 | 8 | n/a | 2.1 | n/a | n/a |
| Conventional | 8002 | 450 | 100 | 8 | 1.9 | 2.7 | 3.4 | 4.2 |
| Conventional | 8001 | 450 | 50 | 8 | 3.0 | 7.7 | 12.4 | 17.1 |
| Flexi-coil windscreen | ER80-015 | 450 | 50 | 12 | 0.8 | 1.3 | 1.9 | 2.4 |
| Bourgault Clearview | XR80015 | 450 | 50 | 12 | 2.4 | 4.2 | 6.1 | 8.0 |
| Flexi/Bourgault Conventional | XR/ER 015 | 450 | 50 | 12 | 2.3 | 6.1 | 10.8 | 15.6 |
| High Clearance | DG11002 | 600 | 30 | 30 | 2.2 | 7.5 | 12.7 | 18.0 |
| High Clearance | TT11002 | 600 | 30 | 30 | 2.9 | 7.7 | 12.4 | 17.2 |
| High Clearance | XR11002 | 600 | 30 | 30 | 6.3 | 14.8 | 23.4 | 32.0 |
| High Clearance (air assisted) | XR11002 | 600 | 30 | 30 | 9.9 | 19.6 | 29.2 | 38.9 |
| Kaletsch Rotary Fans 2000 rpm | XR80015 | 450 | 50 | 12 | 0.4 | 2.3 | 4.1 | 6.0 |
| Kaletsch Rotary Fans 0 rpm | XR80015 | 450 | 50 | 12 | 0.7 | 2.6 | 4.5 | 6.5 |
| *Melroe (ESP on) | XR11002 | 350 | 30 | 23 | - | 6.0 | - | - |
| *Melroe (ESP off) | XR11002 | 350 | 30 | 23 | - | 13.5 | - | - |
* 1997 Preliminary Results
Addendum
Turbo TeeJet Nozzle
Spraying Systems introduced the wide angle Turbo TeeJet (TT) nozzle in Western Canada in 1995. It is classified as a flat fan nozzle, but looks more like a small floodjet tip. AFMRC’s preliminary test results quickly showed the Turbo TeeJet nozzle produced spray droplets somewhere near that of the drift guard (DG) nozzle and spray pattern uniformity to that of the extended range (XR) nozzle. The DG nozzle produced large droplets and very few droplets under 100 microns, and was successful in reducing spray drift. Inadequate coverage from the small DG nozzles and from spraying at low pressures made this nozzle unacceptable with automatic rate controllers. The XR nozzle had very good coverage over a wide range of spraying pressures and heights, making it the choice nozzle for the past six years. The small droplets which are recommended for pesticide and fungicide applications were very drift prone, even in light wind conditions. Timely applications were difficult to attain. As discussed in the airborne spray drift test results, using the TT nozzle resulted in less spray drift.
Spray Distribution Test Results - Figures 1 to 3 show typical spray patterns produced from a standard 8002, extended range XR11002 and turbo TT11002 nozzles. The nozzles were operated at the standard pressure of 275 kPa and standard spray height of 450 mm. Although the application rate across the boom averaged 112 L/ha from all nozzle types, the application rate varied the most from the standard 8002 nozzle and the least from the turbo nozzle. Low drift nozzle spray patterns were similar to standard nozzles.
The coefficient of variation (CV) from the standard, extended and turbo nozzles was 12, 9 and 4 percent, respectively. The coefficient of variation (CV) is the standard deviation of application rates for successive 16 mm sections below the boom expressed as a percent of the mean application rate. The lower the CV, the more uniform the spray coverage. A CV below 10 percent indicates very uniform coverage, while a CV above 15 percent (see bar in Figures 5 and 6) indicates inadequate uniformity. At standard spraying pressures and heights, spray coverage from the standard, low drift, extended range and turbo nozzles were uniform. The CV’s in this report were determined in stationary laboratory tests. In the field, CV’s may differ due to boom vibration and wind. Different chemicals vary as to the acceptable range of application rates. For example, 2,4-D solutions have a fairly wide acceptable range, while other chemicals may have a narrow range.
Spray distribution from Turbo TeeJet TT nozzles was uniform over a wide range of spray pressures and heights. Figure 5 shows how nozzle pressure affected spray pattern uniformity for Turbo TeeJet nozzles and compares them to standard, low drift and extended range flat fan nozzles. The TT and XR nozzles produced acceptable patterns at all pressures tested, from 100 to 600 kPa. Standard and low drift nozzles produced acceptable spray patterns above 250 kPa. These nozzles should be operated above 250 kPa as much as possible. Operators with automatic rate controllers using standard or low drift nozzles should switch the controllers to manual when slowing down to avoid misses at the low nozzle pressures, Figure 4. All nozzle types produced acceptable spray patterns above the standard pressure of 275 kPa. In windy weather, spraying above 275 kPa can also cause excessive spray drift with the extended range nozzles.
Figure 6 shows how nozzle spray height affected spray pattern uniformity for Turbo TeeJet nozzles and compares them to standard, low drift and extended range flat fan nozzles. The turbo and extended range 110° nozzles produced acceptable spray patterns as low as 250 mm above the target. The standard 80° and low drift nozzles produced acceptable spray patterns above 400 mm. All nozzles produced acceptable patterns above 400 mm. Operating nozzles above 500 mm should be avoided to reduce spray drift, especially in windy conditions.
Figures 5 and 6 show the average coefficient of variation (CV) from six sizes of each nozzle type. The sizes included 01, 015, 02, 03, 04, 05 and 06. Turbo TeeJet 06 nozzles are not made. Note that smaller sized nozzles usually have higher CV’s than indicated by the average. Larger sized nozzles have lower CV’s.
Figure 7 shows the coefficient of variation for the TT11002 nozzles after 0, 100 and 300 hours of use. The CV’s increased with time, indicating the spray patterns were getting less uniform the longer the nozzles were used. Visually the spray became more streaky with increased use. Tests showed there were no signs of nozzle wear or plugging. It is believed the nozzle passages changed from certain environmental conditions. However, after 300 hours of use, the CV’s of the TT11002 tips were still below 15 percent. The nozzles could be used for another 200 hours before replacing them.
The CV’s of the TT11003 tips remained unchanged after being used for 200 hours. Streaks in the spray were visible but didn’t effect the spray pattern. It would seem the smaller sized nozzles are effected the most because of the smaller passages. If streaks are present in say the TT110015 nozzles replacing them earlier than the TT11002 or TT11003 nozzles is recommended.
Figure 1. Typical Spray Pattern from a Standard 8002 & Low Drift Nozzles, CV - 12%
Figure 2. Typical Spray Pattern from an Extended Range 11002 Nozzle, CV - 7%
Figure 3. Typical Spray Pattern from a Turbo TeeJet Nozzle, CV - 4%
Figure 4. Typical Spray Pattern from Standard and Low Drift Nozzles Operating at Low Pressures, CV - 25%
Figure 5. Effect of Nozzle Pressure
Figure 6. Effect of Nozzle Height
Figure 7. Spray Pattern Uniformity after Prolonged use.
Cooperators:
Regina Research Station, Agriculture and Agri-Food Canada
Spraying Systems Company Limited
Melroe Company
F.P. Bourgault Industries Ltd.
Flexi-coil Ltd.
Alberta Wheat Pool (Bow Island)
Spencer Hilton (Strathmore) |