Just two issues ago, we featured Drift and its control and presented it as perhaps the most important issue affecting agricultural spray in the coming years. We thank the many of you that contacted us with comments on this problem that could turn into a nightmare for growers all over the country.

As new methods and equipment are introduced to reduce spray drift, we will be testing and reporting on them to bring you our findings and practical evaluations specifically related to applications in intense spray areas such as Florida, Texas and California because we feel that systems developed in the Corn Belt or the Northeast or Northwest may not be totally applicable to sub-tropical and warm growing areas.

Turbo-Drop Nozzle Air-Blast Test.
In our last issue we mentioned the Turbo-Drop nozzle from Greenleaf Technologies. These nozzles are showing promising results in drift control in boom spraying and we wanted to test them in Air Blast machines. The photographs show the results of the test. Drift was definitely and radically controlled and coverage actually improved, even in the upper inside canopy of the trees.

The trees sprayed were Mamey fruit trees planted 20' centers and 2 5' wide rows. The canopy of a grown Mamey tree is considered medium, compared to the heavy canopy of a full-grown citrus tree. The trees had an average height of 16'. We used a Durand Wayland AF40ODP Standard Air Blast Sprayer traveling at 2.5 mph and nozzle pressure set at 200 psi. The control test was done with Spraying Systems Ceramic Disc/Core nozzles at an application rate of 85 GPA. The TurboDrop Nozzles used were TD Red Body with Albuz APE Gray Ceramic Tip and the application rate was 83 GPA. Wind out of the southeast @ 9mph. One-side spraying due to wind conditions.

Observations: Control Test:
Spraying Systems D6CER/25 @ 200psi: Evident fogging exiting vertically out of volute and rising above tree line. Fogging also evident below lower canopy line due to turbulence of lower volute discharge. Drift apparent and estimated at 30% of spray pattern. Appreciable spray cloud also observed exiting opposite side of mid-canopy into next row.

TurboDrop Test:
TD Red/Albuz APE Gray @ 200psi: No vertical fogging observed, no fogging at lower end of volute. Spray pattern apparently directed at canopy. No apparent drifting beyond canopy of tree. Some spray cloud noticed exiting at opposite side of mid-canopy into next row, but now apparently volatile. Absence of turbulent fog around volute and above tree line. Visually, the spray pattern was directed at the canopy and little material seemed to go beyond it. Coverage of inner canopy and undersides of leaves was excellent with little run-off and drip.

Conclusion:
Initially the thought of the TurboDrop producing droplets encapulated in air bubbles gave us reason to believe that the air shear from the volute would "burst the bubbles" and not allow the spray pattern to behave as advertised. The air shear apparently did nothing to disrupt the configuration of the droplets and these accelerated toward the targets and covered them as expected. The coverage with the TurboDrops was just as good as that of the Ceramic Disc/Cores that produce a finer droplet fog and cover inner canopies very thoroughly. Consequently, the same coverage was attained, with practically a total drift control.

Similar testing has been done on Mangos and Papaya, with the same results, except that in the Papaya, the encapsulated droplets from the TurboDrop were able to more effectively reach the taller trees (up to 25') and cover them completely. This bears out the manufacturer's claim that the encapsulated droplets accelerate when leaving the nozzle at a higher rate than conventional droplets. We can certainly recommend this configuration for effective, drift-free air blast tree spraying.

The nozzle industry has been working for several years on nozzles to reduce drift and has previously introduced models that partially controlled overspray and volatilization by producing uniform patter ns of larger droplets. But larger droplets are not always the answer to effective coverage. As a matter of fact, good and economical coverage is attained with smaller droplet patterns which promote canopy penetration and envelop the foliage on all sides, but the down side is that small droplets drift and fly away.

Now, with the development of Venturi air mixing chambers, the droplets leaving the nozzle are actually larger, but really filled with tiny air bubbles that burst upon impact giving a very uniform distribution of the spray material over the surface. TurboDrop nozzles are currently available and word has it that Spraying Systems is about to launch its own version of the air-mix nozzle in a one-piece unit. Stay tuned.