Some chemicals are dangerous, and must be handled with care. The necessary protective clothing is specified on the manufacturers’ label, and should always be worn as indicated. Poisoning can be caused by contact with the skin, as well as by swallowing, breathing in vapour, spray mist or dust.

It is wise to wear oil-proof gloves and rubber boots throughout the mixing and spraying operations, whether stated on the label or not.


Check that the sprayer is clean and empty.

Half-fill the sprayer with water.

Measure out the chemical and reseal the container. When a container becomes empty wash it out and place the washings in the sprayer. Aim to mix just enough chemical for the job. To ensure good mixing, powder formulations should be mixed to a smooth paste in a small amount of water before adding to the sprayer through the filter.

Add the chemical to the sprayer, avoiding splashing. fill from the side opposite the shoulder straps to avoid splashing them.

Wash out the measuring jug, etc. into the sprayer.

Top up the sprayer.

Rinse off any chemical from the outside of the sprayer.

Thoroughly mix the chemical by shaking.


Where specified, remove some protective clothing now that the concentrate is not being handled.

Avoid walking through the sprayed crop.

For ground cover, and low growing crops, hold the lance steady, at a fixed height, and walk at the same speed as the sprayer was calibrated. Avoid leaving gaps or overlapping. Don’t be misled by the width of the hood.

If a nozzle becomes blocked, turn off the spray. Keeping your gloves on, wash the nozzle in water – do not suck or blow down the nozzle. If the nozzle is replaced, the sprayer will need re-calibrating.


Wash hands and face thoroughly with soap and water before smoking, drinking, eating, or going to the loo.

When spraying every day, run clean water through to protect valves and rubber seals.

In the normal way:-

wash out sprayer. Fill the sprayer and pump through, then rinse twice with clean water, pumping through each time. Wash outside of sprayer, including nozzle and lance at least twice with clean water. The washings should run to a soakaway and not to a water course.

Wash all waterproof protective clothing. Be particular to wash the inside of gloves and store them inside out.

Rinse all jugs and containers, including empty chemical containers, and return them to the locked chemical store.

Store protective clothing where it will remain uncontaminated.



To ensure that an accurate quantity of chemical is applied to the ground area, by allowing for variations in the nozzle throughout, and the difference between operators in the speed of walking and the height of the nozzle.


The chemical concentration is adjusted to compensate for these differences.


1. Ensure knapsack and lance are empty.

2. Measure 2 litres of water into the knapsack.

3. Spray a 10 metre strip using the correct pressure – 1 bar (15 p.s.I.) – holding the nozzle at the normal operating height and walking at normal speed.

4. Repeat until the knapsack is empty, counting the number of strips sprayed to the nearest half measure width of spray band.


let a = recommended application rate of concentrate

in kilograms per hectare or litres per hectare.

b metres = width of spray band.

c = number of strips sprayed.

Volume of the full sprayer = 20 litres.

i) Calculate test area

Test area covered = 10 x b x c sq. metres.

ii) Calculate area covered by full sprayer

2 litres covers 10 x b x c sq. metres

20 litres (full knapsack) covers 10 x 10 x b x c sq.m.

b x c f 100 hectares.

iii) Calculate quantity of chemical

It is always true that amount of

concentrate required = application rate x

area covered.

Therefore amount of

concentrate required for

full knapsack = a x b x c f 100 litres or kcr.

( =axbxcxl0 mis. or gms.)

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