Boom Sprayer - SIA

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Boom Sprayer

Research > Agronomy > Extension Services
R. Arscott

One of the most important consideration in an effective chemical weed control programme is proper timing; and with low productivity and increasing scarcity of labour to operate knapsack sprayers, it is often difficult to maintain good timing especially at peak periods. The adoption of pre-harvest burning has further aggravated the situation.
A boom sprayer can help to solve this problem, and can go a long way towards satisfying the spraying capacity on the farm. In fact, it is fast becoming a routine piece of equipment on most farms. Its main is putting on pre-emergence herbicides in both plant and ratoon canes, but it can be very useful in post-emergence weed control where chemicals such as 2,4-D, Actril -D and Gesaprim, which do not retard the cane, are used. Chemicals which are more dangerous to the cane can also be used if they are accurately placed away from the cane, and this can be achieved by using drop nozzles.

As with most equipment, improper use and care of the boom sprayer can lead to wastage of time and time and money. The fact that a boom sprayer has a high output (30 acres more or less per day). Makes it necessary that, for highest return on investment, it should be put to maximum use.
If attention is given to the following points, superior performance from your boom sprayer is virtually assured.

  1. Study throughly the operator’s manual which comes with the sprayer.

  2. Tighten all joints making them leakproof.
  3. Check all nozzles and see that they are the correct type and are fitted with strainers.
  4. Decide on rate of application and adjust the machine to ensure that the desired rate is being applied. (See next sentence).
  5. Check all nozzle for blockage regularly during operation. Remember that the rate of application changes every time a nozzle leaks or is blacked
  6. Use only clean water, free of sediment and debris, to mix the spray solution. This prevents blocking of nozzles and extends the life of the pump.
  7. Spray always at low pressures, 40 - 50 pounds per square inch (psi). High pressure cause drift which wastes chemicals and gives poor coverage where wind conditions are variable.
  8. Maintain constant speed and pressure. This ensure that the right volume of spray is applied.
  9. If none is supplied, install a working pressure gauge in the system - it gives the earliest warning of trouble.
  10. Make sure that an efficient system for in - tank agitation is provided and checked occasionally to see that it works.
  11. It is better to use low volumes to spray (especially in moist conditions) as this reduces refilling and increases the acreage covered per trip.
  12. Maintain the sprayer in good working order. Clean at the end of each day as certain chemicals leave hardened deposits when allowed to dry out.

To apply the right amount of material one must know accurately the capacity of the particular boom sprayer being used, because the rated capacity changes with the age of the equipment. To determine the capacity, do the following:
  1. Fill the spray container to a known mark.
  2. Engage the gear that is normally used when spraying (e.g., lower 3rd or upper 2nd speed).
  3. Engage the power take-off and build up pressure to around 50 psi.
  4. Make sure that the nozzles are clear and that the pump is not leaking.
  5. Travel a measured distance with all nozzles spraying properly.
  6. Check the volume used up by filling up to previous level.
  7. Use the following formula to work out the volume of water per acre in which the chemicals should be mixed.

The Formula:

Key to the Formula
X = gallons per acre
V = volume in gallons used over measured distance
w = width of boom in feet
d = measured distance (in feet)


A farmer whose land is very rolling and of uneven topography may be unable to make best use of a sprayer with a very wide boom. His needs might be better served by purchasing a smaller machine (or even two if his farm is large). On the other hand, on a large farm with fairly uniform topography, one large unit might better serve the farmer’s requirements, since, among other reason, he would then need only one operator. The size of the farm, spraying capacity of the unit, topography of the land cost of the available boom sprayers are all factors which must be carefully weighed when the purchase of a boom sprayer is considered.

Kendal Road Mandeville Manchester
SIA-RD 876-962-2241
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