What is the maximum wind speed a person can spray in with drift reduction nozzles and how do they compare to wind curtains in reducing drift?

I use a Bourgault 1450 with Series II Clearview Air Curtains. The nozzles are the Combo Jet SR80-015 and ER80-03 made by Wilger. I am wondering if I could get the same or better drift reduction without the wind screens by using a drift reduction type nozzle and wonder if they kill the weeds as well?

With conventional nozzles, spraying in wind speeds above 10 mph is not recommended. Using a high clearance sprayer in a 12 mph wind speed, drift was measured at 15 percent using extended range nozzles and 7 percent using low drift nozzles. With the use of air induced nozzles and shrouds spraying can be done in wind speeds up to 15 - 17 m.p.h. However, once wind speeds get over 17 m.p.h. they are no longer steady but gust, and you can easily find yourself spraying in wind speeds well above 20 mph. Many low drift/air induction nozzles and shrouds do not provide enough protection in wind speeds above 20 m.p.h.

Some air induction nozzles reduce spray drift as much as a shrouded sprayer but a large amount of droplet coverage is sacrificed. Many of the new technologies in spraying did not increase our operations in high winds. It still remains at 10 to 15 m.p.h. winds.

Spraying today is done at much faster speeds, with higher boom heights and using less water. The new nozzle technology just tried to maintain drift levels below three or four percent over the past decade to compensate for spray drift increases resulting from changes in spraying operations. If we were to use some of these new nozzles with a conventional pull type sprayer travelling at five m.p.h. we could possibly spray in 20 m.p.h. winds.

More specific to your situation, if the Clearview air curtains do not hinder folding, unfolding, cleaning and installing nozzles or are not an annoyance I would suggest leaving them on since they will always give that extra protection regardless of nozzles used. In a crosswind, especially with ER, XR and any extended range type of nozzles shrouds help reduce drift up to 50 percent.

I would upgrade to a Combo-Jet MR to spray in stronger winds. ER's and XR's will drift and need to be operated with shrouds or lower spray heights and pressures. Yes, there are drift reduction type of nozzles such as the air induced (venturi) type nozzles that can reduce drift as much a shroud or even more. However, these produce very coarse spray droplets that may affect coverage and thus weed control with some chemicals.

With all the studies carried out with air induced nozzles the past decade, researchers have recommended nozzles that produce sprays in the medium and coarse range. Coarse sprays can provide the coverage and drift less in windy conditions than medium sprays. There is no need to operate nozzles that produce fine to very fine sprays such as ER and XR nozzles. Because of the nozzle bodies on your sprayer, you're limited to Combo-Jet nozzles, so for now the MR's are your best choice to spray in windy conditions. I would not go to the Combo-Jet DR's as the spray is getting too coarse. If you are changing your nozzle bodies or inserting adapters to accommodate other manufacturers' nozzles you can consider a list of nozzle options using the sprayer without the shroud.

Answered by Brian Storozynsky, AgTech Centre, Alberta Agriculture and Rural Development

What nozzle is recommended for 30-inch spacing?

It has been suggested to me to change to 15-inch or 20-inch centres. Is this necessary? I farm in Saskatchewan and spray herbicides at 5-10 gallons per acre and fungicides up to 15 gallons per acre, with a Willmar high clearance sprayer at 12-16 mph.

Using 30-inch nozzle spacing on sprayer booms is not something I have promoted, even though some who are selling nozzles have promoted this and there are some farmer testimonials that have indicated typical results. If a producer is using 20 inch nozzle spacing and is contemplating a switch to 30-inch spacing to save on nozzle costs, my suggestion is to think it through.

It has taken over 20 years of nozzle development in the 1980s and 1990s to get spray coverage across the entire width of the spray boom within 15 percent of the average coverage. Even so, 15 percent is still not great. Increasing to 30-inch spacing would require a thorough calibration, especially for 80-degree nozzles, low drift nozzles and air induced (venturi) nozzles. With these types of nozzles, this approach could take us back to the coverage we had in the 1970's with 65 and 80 degree flat fan nozzles.

If a producer has sprayer booms with 30-inch nozzle spacing and relies on automatic rate controllers or GPS control, only wide-angle nozzles like Spraying Systems Turbo TeeJet nozzles, and extended-range nozzle types that produce spray angles above 120 degrees, are recommended.

In addition, to get adequate spray coverage at 30 inch spacing, booms must be operated higher, which will cause more spray drift as droplet velocity dissipates quickly beyond 22 inches from the nozzle tip. It is not worth the aggravation trying to guess on what's happening with coverage and drift at a 30-inch spacing.

Answered by Brian Storozynsky, AgTech Centre

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

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