7.7 Reducing Drift from Airblast Sprayers in Vineyards
The vineyard that the spray has been coming from has 9 foot row spacing, 6-7 foot high vines, and a no-spray buffer zone with a 10 foot wide hedgerow acting as a windbreak. Farmer Brown has a neighbor adjacent to his vineyard and would like to stop any drift from reaching his neighbors property.
Monitoring equipment. Purchase and use good quality instruments for wind speed, temperature and humidity
Nozzle orientation: To see where the spray is actually going, Farmer Brown needs to set up a system to check his sprayer plume. One method is to use a patternator. Another method is to use a 16 foot high pole (two 8' 2"x4" boards end to end) with a paper tape stapled along the leading edge. Place the pole between two vines within the row and spray a mixture of clean water and food coloring. Travel between the rows, spraying out the mixture. The spray will stain the paper where it hits. By looking at the colored spray droplets on the paper, Farmer Brown can alter the orientation of the nozzles or deflectors until the spray is only hitting the portion of the vertical pole/vines that is desirable.
PTO speed: Regulating the PTO speed of the tractor is an inexpensive way to reduce drift. Lowering the PTO speed reduces fan speed, preventing excessive amounts of air from blowing pesticides through the target and allowing good deposition to occur. On an airshear type sprayer reducing PTO speed by 25% reduced drift by 75%. The reduced speed also increased droplet size, further reducing the effects of drift. (NY Fruit Quarterly, Vol. 12 #3Autumn 2004).
Air Induction Nozzles (AI): These nozzles, when used properly, can reduce drift by at least 50 percent. The principle behind these nozzles is to create a larger droplet that won't drift as far but still maintain good leaf and fruit coverage. Note, not all AI nozzles are the same. Remember, it is critical to orientate the nozzles as in step 1 above. Wilger and Lechler manufacture air-assist units to enable AI and hollow cone nozzles to be switched on/off from the tractor.
End Plates: In situations where only one side of the sprayer is required, a shroud can be used to block any air on the opposite side of the sprayer. On the last couple of rows in the vineyard you can spray inwards. This way you can reduce drift by 50 percent.
Axial fan size and speed: Using an axial fan producing 20,000 m3/hr and in conjunction with AI nozzles will result in a 75 percent reduction of drift. In order to accommodate varying crop canopies, e.g. as the season progresses, many modern sprayers are fitted with adjustable pitch propellers to provide a variable airflow.
Cornell Doughnuts: These attachments restricts air intake to reduce air flow through the sprayer. For early season, the 1/2 air intake doughnut can be used to only allow enough air to penetrate just the target row. A 2/3rd air intake hole can be used for early/mid-season to allow more air. Finally in full canopy, no doughnut is required.
Hydraulic Drive: Using a hydraulic motor to drive the sprayer fan will allow you to regulate wind velocity
Tower sprayers are better at targeting the spray into the canopy than a conventional airblast. The conventional air blast sprayer sends droplets in an air blast from a central fan upwards into the canopy whereas the tower sprayer uses a horizontal air curtain.
Foliage Sensors: These sensors tell whether or not the sprayer is next to a vine, automatically shutting the spray off if no vine is present. There are ultrasonic or infrared sensor types and if used properly reduce your overspray and drift by 50 percent.
Tunnel Sprayers: Tunnel sprayers are the best way to reduce drift. Very little spray gets out of the tunnel spraying system allowing for a 90 percent reduction in drift. If A.I nozzles are used with the tunnel sprayer 99 percent of drift can be reduced.
Drift reducing additive: A number of manufacturers supply drift reducing agents, most work via increasing droplet size. Beware not all of them can withstand the higher pressures associated with fruit sprayers and need independent verification
Calibrate and check that the sprayer is functioning correctly
Drift is impossible to eliminate but can be minimized. Implementing just one of these methods will greatly reduce the effects of drift and improve your efficiency of spray application saving you time, money, and future problems.