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• The operation of a backpack sprayer
• Choosing a nozzle
• Calculate amount of spray liquid
• Dosage according to the label when using a backpack sprayer

Most backpack sprayers feature a pressure vessel. This provides constant pressure, ensuring the liquid is sprayed evenly. Some backpack sprayers are equipped with a pressure gauge on the valve, which indicates the spray pressure. A constant pressure is important for a uniform spray pattern. 

You can mount a nozzle on the spray lance of a backpack sprayer. There are different types of nozzles, each of which is suitable for a different application. It is important to choose the right nozzle to obtain the best possible result.

There are two methods to calculate the right amount of spray liquid of a backpack sprayer:
1.    Dosage according to directions on the label.
2.    Dosage according to a solution concentration.

This is particularly suitable for spraying on the ground or on low crops. 

Example: you want to spray a part of the crop with a backpack sprayer. This is 150 x 3 meters. The surface area is 450 m². The label indicates 5 liters of agent per hectare with 200 liters of water.
So for this area, you need: 

• Water: (450:10,000) x 200 = 9 L
• Agent: (450:10,000) x 5 = 0.225 L = 225 ml

The cap release is the amount of spray liquid the nozzle releases per minute at a certain pressure. You can find it in the article about spray nozzels | types and usage for horticulture.

The spray width is the number of centimeters of which the agent hits 100% of the sprayable surface. After all, more spray liquid ends up right below the nozzle than on the sides. That is why you must overlap, so that the same amount of spray liquid is dosed throughout. The entire width the nozzle covers is called the operating width.

In order to see the spray width of a nozzle, it is best to spray on a paved area, such as on the concrete path. 

Note: make sure you always keep the nozzle about 50 centimeters above the ground. This not only works pleasantly, but also provides the best result. 

The nozzle you use has a spray width of 1 m and an operating width of 50 cm. The first and last 50 cm require a half dosage. So in total, you walk 3 times (namely at 50 cm, at 100 cm and at 150 cm). In total, you walk 300 m in 6 minutes. This means your walking speed is as follows:

• 300:6 = 50 m/minute
• 50 x 60 minutes = 3 km/hour
• For a 100-meter distance, you walk 100:50 m/min = 2 minutes

It is important to constantly walk at the same speed and not stand still when spraying with a backpack sprayer. This way, the spray liquid is distributed evenly and you prevent overdosing. 

Dosage according to a solution concentration is usually applied in tall crops. You must determine the required amount of spray liquid by feel and then dose as indicated on the label. 

Example: if you use a backpack sprayer and you want to spray a part of the crop. This is 150 x 3 meters. The surface area is 450 m². The label indicates 5 liters of agent per hectare with 200 liters of water. Then for this area, you need (450:10,000) x 200 = 9 L water.

With a solution concentration of 2%, you calculate the amount of agent as follows: 0.02 x 9 L = 0.18 L = 180 ml.

A higher dosage of spray liquid does not mean the agent works better; in some cases, it is even counter-productive, especially with the use of systemic agents against weeds. In that case, the above-ground part of the weeds quickly burns and dies with overdosing. This means the agent cannot be absorbed in time and the roots are not reached. As a result, the roots survive and grow back.

Safety measures when using a backpack sprayer
To prevent you from coming into contact with the spray liquid, you can take the following safety measures when using a backpack sprayer:

• Always wear personal protective equipment while spraying. Note: also wear the right protection while creating the spray liquid!
• Walk backward instead of forward. This way, you do not have to walk through the mist and will not come into contact with the sprayed crops. 
• Use a (longer) lance instead of a spray gun that is attached to the backpack sprayer.

Using nozzles results in wear. This affects the spray pattern. Therefore, you should check nozzles for wear regularly and clean them to avoid wear as much as possible. 

It is important to always clean a backpack sprayer after use. This is how:
1.    Fill the tank with water and shake carefully. Optionally add some household ammonia or chlorine bleach (note: never add both, because this leads to gas formation).
2.    Spray the remainder over the crop. 
3.    Clean the backpack sprayer externally with water and a brush. Make sure you collect this water, because it may not be discharged as it contains crop protection agents. 

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Which types of spray nozzles are available & how to use them?
Spray nozzles are attachments for spraying equipment used to atomise crop protection products. A nozzle converts a jet of liquid into droplets so that a crop protection product can be evenly distributed over a crop.

How do you choose the right spray gun?
Different tasks require different spray guns. But there are different spray guns per application as well. We help you choose the right spray gun.

Which nozzles are available for high pressure cleaners?
A high-pressure cleaner can be used to easily rinse or loosen dirt. When using this cleaning device, it is important that you use the right nozzle or the right nozzle attachment.