Protect your crops Part 1: What makes a good sprayer?

Protect your crops 1:

What makes a good sprayer?

One of the most important weapons in the farmer’s arsenal is a good herbicide. However, this will do the farmer no good if he cannot apply it to his crops effectively. Having the right tools for the job is of the utmost importance to ensure that you can protect your crops against weeds that can easily diminish your yields. There is a strong correlation between the efficiency of the herbicide and the efficiency of the mode of application.

It is therefore important that the farmer uses effective spraying equipment and to calibrate the sprayer correctly.

It is essential that the farmer has adequate technical knowledge of all the parts of a sprayer before he decides which one to buy. It will save a lot of time and money, and minimise wastage if the farmer understands the sprayer and knows how to operate it effectively.

Sprayer tank

The tank must be made of a material that cannot corrode easily. The inside of the tank should have a smooth surface to make easy and thorough cleaning and rinsing possible.

A tank with a recessed opening will limit spillage when it is refilled. The opening of the tank should be at least 250 mm wide to allow easy access to the working parts inside the tank. It is essential that the tank must have an outlet on the bottom to allow easy cleaning after use.

Filters

The quality of the filters will play a major role in limiting maintenance time and costs on the sprayer nozzles. The filters will prevent any particles from clogging the nozzles that can lead to uneven application in the field. A minimum of two good-quality filters is recommended to ensure smooth operation; one can be a suction filter and the other a flow-through filter. A screen should also be added to the inlet of the tank to catch any larger particles that may be in the water or crop protection product.

Suction filters with screens finer than 100 mesh (around 200 mesh) can limit the flow of certain wettable powders, but is essential when smaller sprayers are being used. Although screens from 150 to 200 mesh can cause problems and uneven spraying by getting blocked partially without the operator noticing it in time, it is still better to use them and clean them regularly. It is easier to clean screens than blocked nozzles.

Effective filters are essential for the effective operation of the spray system. Therefore, they must be cleaned regularly and inspected for damage.

Use a filter that is easy and quick to clean, without having to take it apart.

Certain filters only have a screw top than can be removed for cleaning.

Mixing

A mixer in the spray tank is essential to distribute the chemicals evenly through the water and to keep the solution in suspension, preventing the chemicals from settling at the bottom and causing fluctuations in application quantities. For proper mixing in tanks holding less than 1 000 litres, there should be a separate pipe between the pump and the closing valve, situated in such a way that it continuously mixes the content of the tank. The open end of the pipe should be close to the bottom to prevent material from settling down on the bottom. For spray tanks larger than 1 000 litres a special mechanical mixer is recommended. It is essential for any tank holding more than 2 000 litres.

The pump determines the effectiveness of the sprayer and is therefore one of the most important components. The main tank and mixing tank should be corrosion and rust resistant.

Pump

The pump determines the effectiveness of a sprayer. Many pumps are available with different attributes for different purposes.

Factors determining the choice of spray pump:

• Volume needed per surface area • Pressure needed for reaching the target evenly • Even volume and spray pressure (essential for accurate application) • Resistance to wear and corrosion caused by chemicals • If there is wear or damage it should be easy, quick, and economical to fix the pump. • Service and ease of cleaning can be crucial, especially if different types of chemicals are being used. • Parts should be freely available.

The following pump types are available: Piston pump

A piston pump is possibly the most expensive, reliable, and versatile pump. It handles a high spray pressure and volume and can handle rough and smooth materials

Centrifugal pump

Handles all sorts of materials, even rough, abrasive products. Can deliver high volumes at low pressure.

Diaphragm pump

Handles most types of chemicals. This pump is economical, effective, and also the most widely used spray pump.

Please note:

• Replace the diaphragms every season • Maintain the pressure in the pressure chamber according to specification

Roller pump

This pump is the cheapest, but it is not recommended for the spraying of soluble powders, because the rollers and roller chambers can be damaged. It is only recommended for emulsifying concentrates because wear is an important factor with this pump.

Pipes

Always use quality pipes with smooth interior walls able to withstand the corrosive effect of herbicides. Inspect the pipes regularly and replace if needed.

Sprayer nozzles

The nozzle controls the quantity and the thoroughness of the application.

Nozzle wear

As nozzles wear out, the application volume changes and so does the spray pattern. Tests have shown that some soluble powders can wear out brass sprayers to such an extent that the volume can increase with as much as 24% after 500 hectares have been sprayed. Regular calibration and replacement of these types of nozzles are essential.

Sprayers should be checked regularly to ensure effective application of chemicals. Caring for nozzles

Besides the normal wear/corrosion of nozzles by the chemicals, the spray pattern and delivery rate of the nozzle can be influenced by damaged nozzle openings.

Damage normally occurs when a hard object such as a needle or a piece of wire is being used to remove a blockage from the nozzle.

In no circumstances may a hard object be used to open a nozzle. Rather use a toothbrush or toothpick to clean

Make sure there are no blockages in nozzles.

the precisely shaped opening of the nozzle.

A good sprayer is a vital component for successful crop farming. With farmers leaning more and more towards minimum and no-till farming, a good sprayer can make the difference in making it work. In our next issue we shall discuss the different nozzles and compare the costs of self-propelled, trailed, and hitched sprayers.

Use the correct nozzle for the

chosen application.

A quality mixer in the mixing tank is essential.

Article written by Koos le Roux, compiler of the Mechanisation Guide. Contact him at +27 82-828-9531 or koosleroux@live.co.za.