What are my best nozzle choices?

I have purchased a 4720 high clearance sprayer and I'm looking to spray from five, 10 to 15 gallons per acre at a ground speed of 10 to 15 mph. Can you recommend three nozzles that would cover that range with good drift control and coverage? Also, are double nozzles the way to go?

Basically, farmers have three choices out there: conventional flat fan nozzles, air induction (venturi) nozzles and variable rate nozzles. I and other researchers no longer recommend using conventional type nozzles because drift is the major concern, especially when used on high clearance sprayers. Conventional nozzles can be easily replaced by many of the low pressure venturi nozzles such as the Air Bubble Jets, Greenleafs Airmix and Turbodrop XL, TeeJets and Hypro air induction nozzles.

Use the pre 2005 low pressure air induction nozzles if drift is your biggest concern and the post 2005 low pressure air induction nozzles if your want better coverage. Note, some of the new post 2005 air induction nozzles, especially the twin orifice ones, will drift twice the amount as single orifice ones. In either case, all these air induction nozzles will do the job depending on your assessment of wind speed and your operating boom height.

Boom heights above 24 inches with any of these nozzles make them less effective, so we strongly recommend auto boom height control systems. Our tests show double (twin) nozzles systems are not the way to go and never resulted in better weed or plant disease control. We do measure more spray droplets on grassy type weeds with the double nozzles, but the extra amount is small (less than 8 percent in most cases) and that small amount never translates to better weed control. Increasing from five to 7.5-15 gallons per acre is the better way to go if you require extra coverage on grassy type weeds, since you will have 50 to 75 percent less drift. Double nozzles systems drift 50 percent more than a single nozzle since the orifices are half the size of single nozzles at the same application rate.

Since your application rates are five to 15 gallons per acre, I would recommend trying the variable rate nozzles. There are three to four systems out there but I would recommend the simple VariTarget system. I would recommend the yellow caps for coverage in low wind conditions and the blue caps to spray in more adverse weather and crop conditions.

Answered by Brian Storozynsky, AgTech Centre

Which nozzles will work best?

When using an air induction nozzle at 5 GPA, would two 2.5 GPA nozzles, working in tandem, be better than a single 5 GPA nozzle? and would I receive better coverage than a single 10 GPA whether a air induction or a Turbo TeeJet nozzle? I am thinking about both situations....applying herbicides and fungicides?

We cannot answer this question completely since we do not have spray coverage results for twin nozzles at an application rate of 5 gpa and 10 mph spraying speed. The closest results we have with twin nozzles is at 10 gpa at speeds of 5 and 7 mph.

When comparing single nozzles at the same speed and pressure, coverage is better at 10 gpa than at 5 gpa with this particular air induction nozzle. (See the Chart below from our AgTech Nozzle Selector database). Coverage with the twin nozzles in terms of droplets per square centimeter is usually higher than the single nozzles, especially on grassy type weeds. Note, the horizontal leaf coverage values shown for the twin nozzles at 10 gpa would go down to something near the single nozzle (10004) at 10 gpa if the twin nozzles were tested at 10 mph. Spray pattern percentage, shows the uniformity of the application rate across the spray boom. The lower the spray pattern percentage number, the more even the application rate is. As shown, spray patterns are more uniform with the larger single nozzles.

The coverage numbers provided are close (#/cm²), or would be closer if the sprayer speeds and rate for the twin nozzles matched the single 10002 nozzle. Choosing between single and twin nozzles, in terms of weed efficacy, is not significant enough to say twin nozzles are better. In some cases, depending on nozzle type, rate and pressure, twins show additional coverage on grassy type weeds. Our studies have shown this additional coverage on grassy weeds does not always translate to increased efficacy. Having said this, increasing coverage on grassy type weeds should still be industries ongoing research because as shown on the table, coverage numbers are very low on the vertical cards. The thing that could be a deciding factor in choosing between a single and twin is spray drift. Drift from twin nozzles usually doubles; since the nozzles needed on a twin system are half the size to be equivalent to a single nozzle rate. Going to 10 gpa overall is the best choice since it's the best compromise between coverage and drift, and over the years always has been. The downside to 10 gpa is more work is required to haul and load this water.

Air Bubble Jet air induction nozzle results from the AgTech Nozzle Selector database:

Answered by Brian Storozynsky, AgTech Centre

How far can spray drift move?

Fine spray droplets can move for many miles under the right conditions. They move farthest during temperature inversions (night or early morning) because high humidity keeps them from evaporating and calm air keeps them from dispersing. Topography is also important, as drift will follow low-lying areas. Windy conditions actually help disperse the spray. When it's windy, a greater proportion of the spray will drift, but it also gets diluted rapidly.

Answered by Dr. Tom Wolf, Agriculture and Agri-Food Canada, Saskatoon Research Centre

How low can I go with water volumes and still get good results

The secret to using low water volumes is that coverage is maintained. Since lower volumes result in less water available per square inch, applying this water in smaller droplets compensates. That is fine as long as drift can be managed. Low water volumes typically reduce the effect of hard water. Unfortunately, canopy penetration and overall consistency can be reduced when water volumes are reduced too low. I would not recommend that less than 5 gpa be used for any product other than glyphosate. Remember, water is a relatively cheap input and it offers significant returns in terms of a quality job.

Answered by Dr. Tom Wolf, Agriculture and Agri-Food Canada, Saskatoon Research Centre

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