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Effective Sprayer

Time to check your sprayer

In order to derive full benefit from a sprayer for many years a regular service and maintenance programme should be followed. Before cleaning a sprayer always wear the recommended protective clothing. It is good practice to clean the sprayer immediately after use thereby rendering the sprayer safe and ready for the next application.
  • Remove all filters and clean, replace if damaged or broken. Clean filters ensure that sprayer components such as valves, diaphragms, etc are not hindered or damaged during operation.
  • Remove all nozzles and nozzle filters, clean and check for wear or damage.
  • Check booms for wear and repair any cracks in the metalwork. Check that breakbacks function correctly
  • To perform at their best, booms must be level, and the boom suspension, dampers and joints regularly adjusted and lubricated.
  • Check and grease PTO shaft, replace guard if damaged.
  • Half fill sprayer with water and calibrate sprayer. Check the output of all your nozzle sets individually. If there is more than plus or minus 5% % variation in output this indicates worn nozzles and a complete set of new nozzles should be purchased and fitted.

AIR ASSISTED SPRAYERS

There is an increasing interest in air assisted sprayers. These can give a number of advantages: -
  1.  Increased penetration in dense crops
  2.  Improved work rates through the use of lower spray volume rates (lit/ha)
  3.  50-90% reduction in drift
  4.  Being able to control the deposition of spray on the target location.
The principle is to retain the spray in air and to replace the air in the crop with air from the sprayer, thus reaching all the vegetation in the crop. Get the balance of crop volume, air output, boom height and forward speed correct and excellent results can be obtained.
The main types are: -
  1.  Sleeve Boom Sprayers e.g. Degania, Hardi Twin, and Rau. A hydraulically driven fan blows air into an air sleeve of flexible material with specially designed air outlets.
  2.  Twin Fluid Atomisers e.g. Airtec and AirJet Sprayers. Air is fed from a high volume/ low-pressure compressor mounted on the sprayer while the liquid is fed from a conventional pump. A unique swirl chamber within the AIRTEC nozzle mixes the air and spraymix and the spray emerges in a flat fan pattern.
These advantages have to be balanced against the additional expense of these types of sprayer, typically at least £500.

Hit the Target

The efficiency of spray programmes is determined by the ability of the operator to "hit the target" with as much of the recommended rate of pesticide as possible. One of the most difficult situations occurs when a fungicide is being applied to a heavy, leafy crop canopy where good penetration, retention and ultimately crop coverage is required.

Spray Quality

This is defined in terms of droplet size i.e. fine, medium or coarse.
Coarse droplets much heavier than fine droplets and thus less likely to be affected by drift. However if the crop canopy is heavy and has a high percentage of ground cover then medium-fine droplets are required to achieve penetration, retention and ultimately coverage.
Good coverage is difficult to achieve with the normal flat fan nozzles, so the temptation is to use pressures outside the recommended range (2-4 bar) to produce a finer droplet. In these cases high pressure produces fine spray mists which can drift and are less effective in penetrating the canopy.
To improve crop coverage consider switching from normal flat fan nozzles to twin caps
(Lurmark) or twinjets (Teejet) which produce the same volume of spray through two separate openings.
These openings are situated at the front and rear of the nozzle and increase the potential to hit the target by producing a finer spray quality at a lower pressure. There is the additional benefit of an angled spray which will penetrate the canopy much easier.

Water Volumes

The product label should be followed closely when deciding the water volume to use. Use higher rates when large canopies have to be sprayed. If operators wish to reduce water volumes to increase
work rates and improve timeliness of application then using air-assisted sprayers (Hardi, Rau etc) or the drop leg system (Benest-where the nozzles are suspended from the boom within the crop canopy) is beneficial.
Applying pesticides to crops is a highly skilled operation with the type of crop and the conditions continually changing. Operators must be competent to assess all situations and apply the pesticide at the correct rate to achieve maximise coverage and minimise losses.