Spray to protect your crops
spray 1
extension.unh.edu
Compiled by J Fuls (Pr Eng)
Rain is a blessing, but it may also stimulate an overcrowding of weeds between your precious crops. The knapsack sprayer will be your right hand tool when these times arise. It is therefore very important to know how to use it properly.
This month we shall look at how to use the knapsack sprayer for optimal spraying results. We thank the ARC Institute for Agricultural Engineering in South Africa, who made this article available to the readers of ProAgri Zambia.
Know your sprayer
As with any tool, it is important to know the knapsack sprayer. Study the manual that came with the sprayer and be sure you understand how to use it and what the purpose of each part is.
Maybe someone can help you by making sure it sits comfortable on your back. One cannot do a good job if the sprayer does not sit comfortable.
Practice before you spray in the field.
First practice how hard you must pump, this is, what pressure does one need. If you don’t pump correctly, you will not get the right shape of spray or droplet size from the nozzle.
Fill it with water and adjust the shoulder straps until it fits well. Also feel the handling of the pumping lever while you spray.
Fill the sprayer with water and practice on a piece of clear and dry soil. Note how uneven this spraying is. Practice how to hold the spray lance while walking at a comfortable pace.
Get a good feeling for the correct pressure (pumping speed) and keep to this speed for all the work with the sprayer. It is not as easy as it might seem to spray evenly. The chemicals that you are about to spray are expensive, so one does not want to waste it by spraying too much on some spots. Too much chemicals can also kill your crops.
Also try tying a string from the end of the spray lance to the shoulder strap. This may help you to keep the nozzle steady and at a constant height above the ground.
Always use clean water
The pump inside the spray tank does not like dirty water. Dirt may prevent the valves from working well. A little sand in the water will cause wear and tear on the pump cylinder and piston. The hole in the nozzle tip is also very small and can easily get clogged. So always use clean water in your sprayer.
If you don’t have clean tap-water, cover a bucket with a good cloth and pour the dirty water from the river through the cloth to clean it. Then use the clean filtered water in your knapsack sprayer.
Even a small piece of dirt, like a piece of grass, can cause problems. So, even when you are using clean water, keep the filling strainer in place when filling the tank.
Next month we shall look at the various nozzles to use for different applications.
Published with acknowledgement to the ARC Institute for Agricultural Engineering for the use of their manuals. Visit www.arc.agric.za for more information.
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