VIDEO: Tips for spraying effectively

By: Tom Dickson, Photography by: Andrew Britten, Video by: Andrew Britten

Presented by

When it comes to spraying smartly and effectively, nozzle selection, operating pressure and climatic conditions all play important roles. Tom Dickson spoke to the experts for more information.

Size does not matter. Whether it be a broad acre cropping enterprise spraying tens of thousands of hectares per year or a weekend farmer who only pulls out the little sprayer a couple of times a year the principles of responsible spraying remain the same. Do the job properly.

It’s been made very clear anyone who ignores the directives provided by chemical manufacturers and governing bodies risks harm to the environment, neighbouring crops and the general public.

In cases where it can be proven a person negligently breached responsible spraying practices the perpetrators risk litigation and fines. There is no excuse for ignorance because every drum of chemical sold comes with very clear instructions on the label.

I spoke to spraying experts Silvan, BA Pumps and Sprayers and TeeJet to find out what really matters when it comes to spraying smartly and effectviely.

Important factors to consider include weather conditions, speed, rate, pressure, water quality, maintenance, record keeping and respect for your neighbours.

The main thing to keep in mind is to minimise spray drift as much as possible as drift wastes money, reduces effectiveness, lowers yields and therefore reduces return on investment.

Factors contributing to spray drift are incorrect nozzle selection, operating pressure, wind speed and climatic conditions.


Choose the right nozzle

Spraying Tips Nozzle Selection

All three parties involved in this feature agreed the nozzle is the most important component on a sprayer, so its selection should be well thought-out.

There are hundreds of different nozzles on the market and each is suited to different jobs so my best advice is to contact your agronomist to get some direction on what you may require on your property.

If your nozzles are spread along the boom at 50cm spacing’s then a nozzle with a 110° spray pattern is desirable and the boom must be set at a height of 50cm above stubble canopy to gain accurate spray overlap and even cover.

For an 80° nozzle the spray boom will have to be set higher at 75cm to achieve accurate overlap.

Consider the type of application you want to achieve, finer droplet for complete cover or a coarser droplet size. This will give you an indication of what type of nozzle you require.

Secondly by calculating the rate of application and travel speed you intend to adopt you will be able to select the correct nozzle size from your chosen nozzle type.

By standardising as many of your spray applications as you can you will find you may only need a couple of different nozzles to perform all of your spraying needs.

A set for high volume spraying and a second set for lower volume spraying.


Operating speed and pressure

Fine tuning droplet size and the effects of drift can be achieved by tinkering with your speed and pressure.

To reduce the effects of drift when using an auto rate controller the operator need only slow speed a fraction which reduces the pressure which in turn increases droplet size and prevents the misting effect of the spray.

Slower speeds are always recommended in windy conditions. Once you understand how your sprayer works it is easy to set it up to achieve the best result.

The key is to operate each nozzle type in its correct pressure range. With standard low drift nozzles, the ideal operation is from 2 to 3 bar, avoiding greater than 3.5/4 bar where drift is a consideration.

It is always advisable to carry extra replacement nozzles with you at all times so that damaged and poorly operating ones can be swapped and spraying can resume immediately.

A poorly performing nozzle can greatly reduce spray consistency and rate of application for that particular nozzle. A good policy is replace during the day and repair and restore at night.


Wind speed

Spraying Tips Wind Speed

The next very important consideration is the weather conditions. It is the recommendation to only spray when the wind speed is more than 3km/h and less than 15km/h at the spraying location.

Wind speed can often be difficult to estimate so common sense must be applied and for even greater accuracy a wind speed meter is a good tool to include in your spraying tool kit.

Don’t be misled into thinking zero wind is ideal. The opposite is in fact true. Spray needs a bit of breeze to help the droplets carry in a downward direction. Without breeze a fine droplet can stay in suspension in the air.

Spraying at 15kl/h into a head wind of 15kl/h actually has an accumulative effect of increasing the wind speed on the spray to 30km/h which creates a lot of turbulence on the delivery of spray.

With this in mind there’s still the question of whether it’s safe to spray at high speeds. Where possible it is recommended to work with a side breeze to maximise a consistent spray pattern.

Spraying at night can often provide a false sense of security because the cool, calm conditions can be mistaken for an optimum spraying opportunity. 


Temperature inversion

A temperature inversion is a thin layer of the atmosphere where the normal decrease in temperature with height switches to the temperature increasing with height.

An inversion acts like a lid, keeping normal convective overturning of the atmosphere from penetrating through the inversion.

This can cause several weather-related effects. One is the trapping of pollutants below the inversion, allowing them to build up. If the sky is very hazy, or its sunsets are very red, there is likely an inversion somewhere in the lower atmosphere.

In this situation a fine mist of chemical can be drawn up but trapped under the inversion then transported to another location outside the targeted spray area.

If many operators are spraying in these conditions a lethal cocktail of chemicals can drift together then settle in valleys and gullies. This scenario can cause neighbouring crop damage but can also create severe health risks to humans as well.

TeeJet technical specialist Jake Lanyon says products like 2,4-D can travel long distances under the right conditions, potentially up to 30 kilometers.

"So it is important to consider spraying times," he says.


Delta T

Spraying Tips Delta T

Delta T is a term all spray operators should familiarise themselves with. It is the measure of evaporation or survival of spray droplets.

When the Delta T reaches below 2 or above 8, spraying should stop. Continuing risks drift of chemical off the desired target.

Nozzles that produce larger droplet size help avoid the effects of spraying during unfavourable Delta T conditions.

Listen to your gut feeling. If you have any doubts about the suitability of the spraying conditions or your equipment stop immediately.

When chemicals are involved if you are not getting maximum efficiency you are wasting your time, money and most importantly the health and wellbeing of yourself and your neighbours as well.


Know your water

As a general rule of thumb, if the wateris suitable for drinking it is presumed to be of acceptable quality for spraying.

Knowing your water quality and how to treat it can greatly improve the outcome of spray operations. Poor water quality can adversely affect many spray jobs, particularly when products remain in the tank for extended periods or where high water rates or low rates of product are used.

Many pesticides are affected by poor water quality and it is important to test a water source before using it for spray operations.

Water tests for spraying operations should include:

  • pH
  • total hardness
  • bicarbonate levels
  • either total dissolved salts (TDS) or salinity (electrical conductivity, EC).


Alkaline water (pH above 8) can cause pesticide problems including alkaline hydrolysis and increased breakdown of the product, poor droplet contact with the target and reduced performance or stability from some formulations and adjuvants.

A typical pH meter can be purchased from most electronics stores at a cost of about $50 to $80. It is a cheap investment relative to the cost of the chemical being used.

Total hardness

Total hardness is a measure of the amount of cations, or positive ions such as calcium, magnesium, sodium, iron and carbonates in the water and is usually expressed in parts per million (ppm) or milligrams per litre (mg/L) of calcium carbonate equivalents (for example, CaCO3 mg/L).

Calcium and magnesium can bind with negatively charged products, such as weak acid herbicides like glyphosate, causing them to lose their activity in the target plant.

Water hardness above 250 to 350ppm (CaCO3 equivalents) should be treated before using some herbicides, particularly when pH is above 7.

Salinity (dissolved salts)

Salinity is usually measured as the electrical conductivity (EC) of the water. High levels of salinity (above 1000ppm sodium chloride or ECs above 500 to 1000 microsiemens per centimetre) can result in some chemicals precipitating out of the solution and others being inactivated.

High salinity can also make it difficult to adjust pH using buffers. Often the only solution for highly saline water is not to use it for spraying, or to greatly dilute it with clean rainwater if available.

Dirty water (suspended solids)

For some chemicals, such as Trifluralin, muddy water will not reduce chemical efficacy as it will be incorporated into the soil but dirty or turbid water can adversely affect products such as Spray.Seed® and glyphosate due to the clay colloids suspended in the water.  

As a general rule, if a 10 cent coin cannot be seen in the bottom of a bucket of water it is too dirty for use with products affected by dirty water.

Filtering water and settling it in a holding tank before use can help reduce turbidity but if using a settling agent, such as alum, only very small quantities should be used in accordance with the manufacturer’s guidelines.

Often too much alum is added to dam water, which can result in high levels of aluminium in solution. This increases hardness and creates more problems for several products than the untreated dirty water alone.


Check all systems

Spraying Tips Check All Systems

Once you are confident you have installed the correct nozzles for the job, the water is of good enough quality to avoid adversely affecting the results and you have a good handle on the desired weather conditions for responsible spraying, then it’s time to carry out a few last minute operational checks of your spraying equipment.

Silvan Spraying and Machinery Product Specialist Raph Hymus insists it’s a priority to know how your sprayer operates and check for anything that could reduce its effectiveness.

Read the operators manual to familiarise yourself with your sprayer. Periodically check all the nuts and bolts on the boom and frame for correct tension, especially the ones that attach the pump to the frame.

Regularly apply grease to all the grease nipples and pivot points and check that all the breakaway points on the boom are operating properly.

Inspect and clean filters often to prevent contamination from entering the spray line and blocking nozzles.  Any nozzle that appears to be performing differently from the others should be removed and replaced.

Check that there is sufficient oil in the pumps reservoir. Milky looking oil could indicate the spray mix entering through a crack in the pump or leaking seal. This needs to be addressed immediately before sever damage and possible pump failure occurs.

Safety must also be considered when spraying. Gloves should always be worn when handling chemicals and in some cases, especially with pesticides, breathing apparatus should be worn.


Keep record

Good practices also include keeping a thorough history of all your spray applications including date of application, area sprayed, chemical used, rate, nozzle description and weather conditions.

Apart from improving your management skills it could be evidence used if you ever need to defend yourself against litigation.


Last word

Poor spraying practices could result in damage to the neighbour’s canola or maybe the death of the wife’s roses but either way you will have a lot of explaining to do and compensation to pay.

So do the right thing and get it right. Pick up a TeeJet nozzle selection guide. Maintain your sprayer in top working order. Find out what the quality of your water is like. Know how the weather can affect the spray application and most importantly if in doubt call an agronomist.

The representatives from TeeJet, Silvan and BA pumps and sprayers all say they are always available for advice on best spray practices.

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