Application Technology : Care and Use of Equipment

Table of Contents

1. Spraying Speeds
2. Water
3. Agitation
4. Pumps
5. Nozzle Tips
6. Cleaning the Sprayer
7. Other topics in Application Technology
   • Introduction
   • Sprayer Calibration
   • Determining Amount of Herbicides Needed
   • Materials, Mixing and Mixtures
8. Related Links

Spraying Speeds

Because most agricultural and roadside herbicide must be uniformly applied, the forward speed of a sprayer must be constant whenever the nozzles are delivering liquid. If the driving wheels of a tractor slip on the soil surface, the tractor's speedometer does not indicate a change in forward speed. To be certain that the forward speed is constant in spite of wheel slippage on hills, use an independent speedometer powered by a non-driven wheel. Spray monitors and other electronic rate controllers also may be installed. Only rate controllers will automatically adjust for variation in tractor speed to maintain a constant rate of application.

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Water

Use only clean water that contains no debris, sand or mud. On your farm water supply, use a frost-free water hydrant located outside the building. An anti-backflow or antisiphon valve should always be installed on any hydrant or water supply. Never allow the intake screen to rest on the bottom of a farm pond while filling a sprayer. The intake line near the screen must, by law, be equipped with a check valve or anti-backflow device to prevent contamination of the pond or stream when the pump is shut off. The use of a tank-refilling nozzle, volume-booster nozzle or injection pump to aid in refilling the sprayer tank from farm ponds or streams must be avoided. These tank-refilling aids may cause pond or stream contamination.

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Agitation

When chemical formulations in solution are used (2,4-D and water) at least 2-14 L/min should be returned to the tank for agitation within the tank. Higher rates will apply with wettable powders. To be effective, the agitation line from the pump should pass through a control valve and deliver the liquid to the bottom (not the top) of the tank. Agitation nozzles or a sparge tube should always be used to ensure sufficient liquid circulation in the tank.

When wettable powders (atrazine, etc.) are used, the return to the tank should be 14-27 L/min for each 450 L of tank capacity, depending on the concentration of the wettable powder and the size of the tank. A dedicated line from the pressure side of the pump (not the pressure regulator) to the tank must be used to carry the liquid necessary for hydraulic agitation in the tank. Always use a venturi jet or sparge tube. This flow can be reduced if the sprayer has a mechanical agitator. Sparge tube agitation requires more water than venturi to give the same agitation.

Avoid excessive agitation of the mixture, as it may turn into an invert immulsion, a grease-like mass that will settle to the bottom of the tank and cannot be pumped. Excessive agitation may also cause foaming resulting in pumping problems. To prevent a build-up of oil in the sprayer, the tank should be emptied completely before refilling. After any break in the spraying operation, agitate thoroughly before proceeding. Clean the tank and sprayer immediately after use with a detergent or solvent and flush with clean water.

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Pumps

The pump is the most important part of the sprayer. The pump should have adequate capacity to maintain the desired pressure, volume and agitation. Piston, diaphragm and centrifugal pumps are the best for pumping wettable powder suspensions. For liquid herbicide applications, roller pumps may be used in addition to the above types. When used for wettable powders or flowable formulations, choose a pump with an abrasion-resistant housing. Carefully follow the manufacturer's care and storage instructions for the best pump performance.

CAUTION: Running a spray pump without water may cause damage or premature wear.

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Nozzle Tips

Numerous companies make spray nozzles. These may be similar in design but may have slightly different setup requirements to get uniform spray coverage. Always follow manufacturers' recommendations for nozzle spacing / nozzle-to-target distances. These distances may vary according to the spray angle of the nozzle. Proper geometry is essential to ensure adequate overlap of adjacent nozzle spray plumes.

Care should be taken to maintain a stable boom height to assure uniform overlap of the nozzle spray patterns.

The success of the spray application is dependent in part by on the condition of the nozzle tips and uniformity of application across the whole spray boom. The spray pattern of all nozzles should be examined prior to their use. In addition, each and every nozzle should be checked when calibration of the sprayer is done.

Materials used for nozzle tips range from brass, stainless steel, hardened stainless steel, as well as plastics/polymers and ceramics. All product formulations and carriers cause wear of the nozzle orifice, wettable powders more than others do.

Sprayers should be calibrated routinely. (See note on calibration below.)

Nozzle tips should be replaced when they deliver 10% more than manufacturer's rated output specifications. Worn nozzle tips may provide uneven distribution of spray solution and cause changes in the spray pattern. This may result in uneven delivery and produce streaks across the field. Flat fan nozzle tips are widely used on boom sprayers to apply herbicides. Spraying operating pressure should be within recommended limits outlined by the nozzle manufacturer. Nozzles with a 110 degree spray angle have more overlap than 80 degree nozzles, resulting in a wider spray angle, which allows less chance of spray skips as the boom moves closer to the ground. Always follow manufacturer's recommendations for spacing and minimum nozzle to target distance and spray operating pressures.

Flat fan nozzle tips that will operate at reduced pressure, approximately 140 kPa, are available. These nozzle tips can further reduce the potential of drift.

Air induction or venturi nozzles are now available from at least ten different companies. These nozzles were specifically designed to reduce the amount of fine droplets produced in the smaller nozzle sizes. The nozzle manufacturers offer air induction or venturi nozzles in a wide range of sizes.

These nozzles draw air into the nozzle as the spray liquid passes through the nozzle. The end result is the production of a coarse spray with very few fine spray droplets that are drift prone. These coarse droplets contain air bubbles that cause the droplets to rupture upon impact with plant surfaces.

Air induction nozzles are made in two pressure ranges, low pressure and high pressure. If your sprayer cannot exceed 345 kPa, you should only consider a low-pressure design. All venturi nozzles should be operated in the middle of their working range. For the low pressure designs this is approximately 275 kPa and in the high-pressure designs, about 550 kPa. All venturi nozzle designs are extremely sensitive to low working pressure. The spray patterns will collapse to less than their designed spray angle if the nozzle pressure is too low. This will result in a distorted spray pattern. In addition, the induction of air into the spray liquid will not occur if the pressure goes below a certain point.

Many producers have quickly adopted this new nozzle technology. The significant reduction in spray drift, compared to conventional flat fan nozzles, is a welcome feature. Some producers are using these nozzles for all their herbicide spraying. Some product performance problems have occurred when air induction or venturi nozzles have been used. One or more of the following factors may contribute to this. Poor timing of spray, reduced water volumes, spray pressures that are too low and difficult-to-wet weeds may all contribute to poor control.

Special even-spray nozzle tips are available for band spraying applications of herbicides. These even flat fan nozzles deliver a uniform amount of spray over their sprayed area. A variety of sizes, spray angles and nozzle materials are available. The nozzle-to-target height, and spray angle of the nozzle tips as well as its orientation to the direction of travel, determines controls the width of the sprayed band. Carefully follow manufacturer's literature and directions.

Flooding nozzle tips are used at low pressures and, because of their wide spray angle, can be used closer to the ground surface, thus reducing the drift hazard. New flooding nozzle tip designs have improved the spray distribution patterns to the point that it is as good as with the flat fan tips. Flooding nozzle tips are available in brass, plastic/polymers and stainless steel. Half as many of these nozzle tips are required to cover the same width as would be required with flat fan nozzle tips. Sprayers equipped with a broadcast type of nozzle cover a wide swath. They are especially convenient for farm lane and fencerow spraying where a uniform spray pattern is not essential. The spray pattern is affected by wind and severe drifting may occur with even a light breeze. Never use a broadcast-type of nozzle to spray near a susceptible crop.

Full or hollow cone nozzle tips may be used for applying herbicides to the soil surface when the herbicide is incorporated or mixed into the soil with a disk harrow, cultivator or similar tillage implement.

NOTE: When using any nozzle for spraying wettable powders or micronutrients, it is essential to calibrate the sprayer frequently because, as a nozzle wears, the quantity of spray material delivered increases and distribution is uneven. Worn nozzles usually produce will result in a very poor spray pattern.

Nozzle manufacturer's catalogues will list screens required for various nozzle types and sizes. Diaphragm check valve nozzle bodies will ensure dripless operation when the boom is turned off. To clean nozzle screens, remove them from the nozzle bodies and wash thoroughly with soap and water, using a nozzle tip bristle brush. Simply flushing water through the boom and nozzles will not remove pesticide residue that has built up on the outside of the nozzle screens.

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Cleaning the Sprayer

Before cleaning the sprayer, dispose of surplus tank mix. As suggested in the Grower Pesticide Safety Course, one method of disposal is to dilute the remaining spray solution at least 10:1 with water. This diluted solution can be applied to the previously treated area as long as the maximum recommended product rate on the label, is not exceeded.

Clean out the sprayer immediately after finishing the day's work or when changing chemicals. At the end of each spray day, thoroughly flush out the boom with plenty of water to rinse lines, diaphragm check valves and nozzles. Delaying cleanout, even overnight, can allow the formation of hard-to-remove deposits. If allowed to dry, the sprayer tank is much more difficult to clean. Residue buildup can also result from numerous applications of a herbicide over a period of days or weeks with no cleaning or rinsing in between. Don't forget to also clean out the measuring containers.

Steps:

1. Read the product label to determine the recommended cleaning procedure. Have ready all the materials required for the cleanup, including appropriate personal safety equipment.
2. Drain spray tank.
3. Fill tank with water and add detergent, ammonia or other tank cleaner product and allow to agitate for 10-20 minutes (clean the whole tank not just the bottom half). Flush boom and hoses with solution, allow to stand for several hours (or overnight if possible) and then flush boom and nozzles again and drain tank. When flushing the boom, open the boom ends to get particles out of the boom.
4. Inspect inside of tank for visual residues; rinse inside of tank if necessary. Repeat step 2.
5. Wash outside of sprayer with soap or mild detergent and water.
6. Remove nozzles, screens, and wash separately in a bucket containing cleaning solution. Don't forget to wash out your measuring container with the cleaning solution.
7. Remove all boom end plugs or caps. Product residues collected in the ends of the various boom pipe sections could cause crop injury. Thoroughly clean out the plugs or caps and pipe ends with cleaning solution. Carefully replace all the boom end plugs or caps.

Thoroughly rinse the tank, hoses, booms, nozzles and screens with clean water for a minimum of 10 minutes. Repeat immediately before your next use.

Use household detergent at rate of 250 mL/100 L or 1 kg/150 L of water. Use ammonia (3%) at 1 L/100 L of water. Use other cleaning agents according to label directions. Never mix ammonia with chlorine bleach. Chlorine gas is produced which may cause severe eye, nose, throat, or lung irritation.

NOTE: Contact the manufacturer of pesticides being used to determine the best methods and product(s) to clean residue from tanks and associated equipment. Read the label, since many products, e.g. Accent, Banvel II, Conquest, Peak, etc. provide tank-cleaning information on their label. Some products such as Agral 90, or All Clear, are recommended as tank cleaning agents.

Do not use equipment that has applied Group 4 (2,4-D, MCPA and related phenoxy herbicides) or many of the Group 2 herbicides to spray fungicides or other materials on susceptible crops and do no park or store near greenhouses or other areas where susceptible crops are grown.

Clean the spray tank, booms and hoses first. Be sure to also clean the nozzles and tips, screens, filter, strainer and pump. These parts are often overlooked, and can trap residues. Because of today's highly active, low-use-rate herbicides, it is essential to clean out every trace of herbicide.

When surfactants or fertilizer solutions (e.g., Agral 90, 28% UAN) are used in a recommended mix with herbicides, there may be some inadvertent cleaning of previous residues from the tank/equipment that could affect the crop. Proper cleanout when changing products is essential to prevent crop injury.

The wash water contains herbicide. Never allow wash water to run into a well, lake, pond, river or other water source.

Do not leave puddles that may be accessible to children, pets, farm animals or wildlife.

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Related Links

• Weeds in Ontario
• Engineering topics
• Problem Weed Control in Field Crops
• Integrated Pest Management (IPM)
• Pesticide Application and Safety
• Pesticide Companies and Agents
• OMAFRA Sprayer Calibration Calculator
• Search the PMRA website
• OMAFRA Publication 505: Ontario Weeds
• OMAFRA Publication 75: Guide To Weed Control

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