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Four Rules For Nozzle Selection

The field sprayer has become the most used implement on many farms. While the tractor, air drill and combine typically make one pass over the land each year, the sprayer may make multiple passes — doing a pre-seed burn-down, applying herbicides, fungicides, insecticides, desiccating and even adding micronutrients and fertilizers to the crop.

Because of the multi-functionality of the sprayer, many farmers are investing $200,000 and more in a high-clearance sprayer that promises the capability to handle all of these tasks. It’s surprising then how many farmers balk at spending $500 for a set of new nozzles for the sprayer. After all, the nozzle is arguably the most important component on a sprayer. “It is the nozzle which largely determines the efficacy of the pesticide, the amount of drift, and the overall satisfaction with the spray operation. All the other components — the horsepower, the suspension, the size of the tank, simply support the operation of the nozzle,” says Tom Wolf, research scientist with Agriculture and Agri-Food Canada, Saskatoon.

Perhaps the fact the cost of nozzles make up less than one per cent of the investment in a new sprayer is the reason many farmers pay such little attention to them. However, not all nozzles are the same, not all can do the same job, and unless you match the nozzles to the task at hand, you will not be satisfied with the performance of the application, no matter how big or shiny the sprayer is.

MATCH NOZZLE TO USE

According to Wolf, there are four rules for nozzle selection. The first rule is to know what you need your sprayer to do and select a nozzle that is best for meeting those needs. There are four basic categories of nozzles and each has advantages and disadvantages.

The conventional flat fan nozzle is the best for low water volumes but is very drift prone and cannot be used at high pressures (use at 20 to 60 PSI). The pre-orifice nozzle will reduce drift by up to 50 per cent, but is not quite as good at low water volumes as the flat fan nozzle and requires a slightly higher pressure (use at 30 to 60-plus PSI). The low-pressure air induced nozzle reduces drift a little more (50 to 70 per cent) at 30 to 60-plus PSI but should not be used if applying volumes of less than five gallons per acre (gpa). The high-pressure air-induced nozzle provides the best drift protection (70 to 90 per cent reduction) but requires pressures over 60 PSI and should not be used for applications of less than seven gpa.

Water volume is of prime concern to most farmers, and matching the water volume to the spray task is Wolf’s second rule in nozzle selection. “The coarser your spray, the higher the water volume must be,” says Wolf. He explains very coarse sprays may not provide enough droplets per square centimetre to hit all weeds, especially when they are very small as are typically found in pre-seed burn-off applications. Contact herbicides (Groups 6, 10, 14, 22, and 27), insecticides, and fungicides also need higher water volumes to provide enough coverage for the pesticide to be effective. Finally, the taller and thicker the crop canopy, the more water that is needed.

WATER VOLUME

PRESSURE CONSIDERATIONS

The third rule, according to Wolf, is consideration of the pressure you will be using. Every nozzle has an optimum operating pressure which provides the intended droplet size and the proper spray pattern. Each nozzle also has a working range at which the nozzle provides acceptable coverage. Increasing pressures beyond the working range decreases droplet size and increases drift. Pressures below the recommended rates for that nozzle will result in a poor spray pattern. Choose a nozzle for which the midpoint of the operating pressure range matches the pressure you want to spray at. This ensures the nozzle will still provide satisfactory results as the pressure varies as you speed up and slow down.

UNIFORMITY

Finally, a farmer needs to select a nozzle that will provide a uniform spray pattern across the boom. Ideally, you want 100 per cent overlap of nozzle coverage. You already know the nozzle needed for the speed and pressure at which you will be operating at, so now you must determine the nozzle angle to give you the proper pattern overlap for the boom height you will be operating at.

Once you have identified the nozzle you need, you can refine your choice based on material the nozzle is made of (plastic, stainless steel, ceramic), nozzle orientation, (straight down, backward, forward, or dual tip), manufacturer and, of course, cost.

Nozzle manufacturers are assisting farmers in making informed choices by publishing detailed spray-quality charts that identify droplet size at various pressures, flow rates and travel speeds for each size of nozzle. As well, nozzles are now colour coded by size.

Also, droplet size has been colour coded to give growers a quick visual representation of the quality of spray they can expect. Droplet size colour coding is: red — very fine, brown — fine, yellow — medium, blue — coarse, green — very coarse, and white — extremely coarse droplet size. These charts are available in spray catalogues as well as online on manufacturer’s websites.

“When selecting a nozzle, you must first know your needs. Then select a nozzle that not only meets those needs, but will work well over a wide range of pressure and travel speeds. Almost certainly, growers will need more than just one nozzle given the range of spray operations. And there is no nozzle that will rescue you if you do not follow good spray practices,” says Wolf.

GeraldPilgerfarmsatOhaton,Alta.

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What’s New In Nozzles

Here’s a rundown of what’s new in nozzles for the Canadian market this year.

HYPRO GUARDIANAIR

This new spray nozzle is the result of a collaboration of research between HyPro and Syngenta. It offers a number of unique features including a rearward spray incline of 10 to 13 degrees which provides more complete plant coverage at high travel speeds. This nozzle also creates more droplets per gallon of water than most other air-induced nozzles.

The biggest feature of this nozzle is that it offers a consistent spray pattern of medium and coarse droplets at a wide range of pressure — from 15 to 115 PSI.

It is available in seven different sizes to offer growers an optimized nozzle for travel speeds from three to 20 miles per hour.

TEEJET AIR INDUCTION TWIN JET

This is an air induction flat fan nozzle that creates both a forward and rear spray pattern with 60 degrees of separation. This twin pattern increases coverage and crop penetration.

This tip has a working pressure range of 20 to 90 PSI and is available in six different sizes for a wide range of travel speeds.

The nozzle offers excellent drift control by producing coarse to very coarse droplet sizes and is ideally suited to post-emergence applications.

C-SPRAY CVI TWIN

This is a new, low-pressure, air induction, dual-pattern flat fan nozzle. It offers 65-degree separation between the forward and rear-facing spray patterns to provide better crop penetration.

What makes this nozzle unique is the ceramic insert which provides both chemical and wear resistance resulting in long-lasting precision. The ceramics also allow this nozzle to be used with any types of chemicals and fertilizers including acids. Ceramics can last up to 10 times longer than stainless steel nozzles.

This nozzle provides a uniform spray patter at 20 to 60 PSI. The coarse droplets produced at this pressure result in very low drift potential.

HARDI MINIDRIFT DUO

This is a twin-pattern nozzle with 30-degree forward and 30-degree rearward spray patterns to provide better penetration of crop canopy and coverage of leaf surface.

This nozzle produces a medium to very-coarse pattern at a wide range of pressures, and also has large air inlets to minimize the risk of blockage and to facilitate cleaning of the nozzle.

While there are six sizes of the Minidrift nozzle available in North America now, the Minidrift Duo is still only sold in Europe. However, it is expected the Minidrift Duo will be available some time in 2011 in North America.

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