Tips on herbicide Application and knapsack calibration

Of course applying granules is one thing but the one process in the garden that really freaks gardeners out is applying herbicides using a pressurizes pedestrian sprayer.

Calibrating your equipment is essential and following some simple rules will ensure you are not ripping the lawn up and starting again.

Its not just about lawn health either. As a user you have a responsibility to protect other people and the environment.

Simple Guide to Calibration.

To apply your chemicals you firstly need a good sprayer. Cooper Peglar is as well known as any make if not the most popular with professionals.

When you purchase a sprayer you will normally be supplied with a fan, cone and anvil nozzle. Choosing the right one is difficult and is more complex depending on the type of chemical to be applied. A rule of thumb is an anvil nozzle has a larger hole and is used to apply thick gloopy liquids, usually moss killers. The fan is used for herbicides because, like an anvil, it gives a wide swath and the cone is for insecticides or spot treatment. There is an international colour code for nozzles so it will pay to read any literature you receive with your sprayer to determine what you have. To purchase nozzles click here.

Firstly and most importantly make sure your sprayer is neutralised

Simple Calibration

When it comes to amateur use there are a few simple procedures to master.

Lets say the manufacturers advice is to apply 150 ml of chemical per 100 square metres of lawn.

Firstly, fill the sprayer with 3-4 litres of water.

Pump the sprayer until up to working pressure and then release the trigger so that you release the water into a bucket. Time this and stop after 2 minutes. You then need to measure the amount of water in the bucket. Make a note of this.

Next, aim the lance at a height of 50cm onto some dry concrete and measure the width of swath. Lets say the swath was 100 cm wide.

Then, with your knapsack on your back, simulate spraying over a 50 metre distance and make a note of your time.

You then need to put all this info together.

These results below are hypothetical:

2 minutes of spraying into bucket = 2 litres

width of swath = 100cm

time to walk 50 metres = 30 seconds

Multiply 2 litres by 1000 to give your reading in millilitres. Divide 2000 by 120 seconds to give you a rate of application per second (16.6 ml a second)

You know that your swath width is 100cm and you walked 50 metres so your coverage was 50 square metres. You took 30 seconds walk 50 metres so 30 (sec.) x 16.6 (ml) is equal to applying 498 millilitres to 50 square metres of ground.

Now you know that your area of lawn is conveniently twice the test area that you calibrated your equipment over so you need to add 996 ml to your sprayer to which you add your 150 ml of chemical.

By covering your lawn at the same walking speed at the same lance height as your calibration test you cannot fail and it is worth doing this process for every nozzle you might choose to use. For a more in depth explanation of nozzles click on this Monsanto PDF page.

It pays to be a responsible operator, not just for your lawn but the environment as well.

It can be more complex and for the professional there are now quite stringent regulations and every operator has to have a Proficiency certificate  (NPTC). Every operator has to undertake a basic module called a PA1 which relates to the safe use of pesticides in general and if you intend to use a knapsack sprayer then your particular certificate will be a PA6a. This means you will have been tested at a center and are regulated by a code of practice.

After this you will have a legal obligation, not just a moral one for the safe and efficient use of pesticide's.

Even if you use pesticides (name given to all horticultural chemicals) you will be considered a responsible gardener if you enrol on this course. Revision can be done at home and the test usually takes just one day (if you pass) and costs between £85-£115 depending on your testing center.

Tests can be taken at most Horticultural or Agricultural Colleges or at the premises of training organisations who have the the more advanced BASIS registration.

For garden use, this resource is a good guide but for an in depth resource in the safe use of pesticides click here.

Please also read:tips on calibrating a fertiliser spreader.