Sprayers
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Insect pests and weeds cause considerable damage to the commercial crops. If not controlled in time, the entire crop gets lost and, therefore, farmers are likely to suffer in many ways. Among the important methods of weed control and plant protection systems, the following methods have been recognized as the effective and economical ones under

different situations:

a) Mechanical control
b) Chemical control
c) Biological control
d) Agronomical methods
e) Bio-physical methods
f) Fire as control

The mechanical control of weeds is most widely used in India and in many developing countries due to the availability of farm labour at relatively low rates of wages. Whereas, the chemical method of plant protection has been universally accepted due to saving of time, labour and its effectiveness with relatively low expenditure. In developing countries, combination of chemical and mechanical methods of weed control has been successfully accepted. The chemicals for protecting the plants from various injurious or organisms need to be applied on plant surfaces in the form of sprays, dusts, mist etc. Sprayers and dusters are available in many forms for this purpose.

Purposes of Sprayer:

Sprayer is a machine to apply fluids in the form of droplets. Sprayer is used for the following purpose: (i) application of fungicides to minimize fungal diseases, (ii) application of insecticides to control insect pests, (iii) application of herbicides to remove weeds and (iv) application of micronutrients on the plants. The main functions of sprayer are:

(i) to break the liquid into droplets of effective size, (ii) to distribute them uniformly over the plants, and (iii) to regulate the amount of liquid to avoid excessive application

Desirable quality of sprayer

(a) The sprayer should produce a steady stream of spray materials in the desired fineness of the particle so that the plants to be treated may be covered uniformly.
(b) It should deliver the liquid at sufficient pressure so that it reaches all the foliage and spreads uniformly over the surface of the plant
(c) It should be light weight, sufficiently strong, easily workable and repairable.


Sprayer
Sprayer’s classification
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Based on power source, sprayers may be classified as:

(i) Hand operated machines – suitable for small holdings. They are operated at pressure ranging from 1 to 7 kg/cm2.
(ii) Power operated machines – suitable for treating a large area. They are operated at pressure ranging from 20 to 55 kg/cm2.
(iii) Air planes – suitable for large scale work.

Based on spray volume, sprayers may be classified as:

(i) High volume sprayer - More than 400 litres of spray liquid per hectare is used.
(ii) Low volume sprayer – Spray volume ranges between 5 to 400 litres per hectare is used.
(iii) Ultra-Low volume sprayer – Spray volume less than 5 litres per hectare is used.

Based on working principle, sprayers may be classified as:

(i) Hydraulic energy sprayers
(ii) Compression sprayers

Hydraulic energy sprayers : In this category of sprayers, hydraulic pressure is thrust upon the liquid by the hand operated pumps. As a result, the liquid is forced through the nozzle in the form of a spray of droplets (diameter in the range of 300-400mμ). Sprayers of this type are high volume, high pressure and suitable for complete coverage of both ground and field crops. 96

Bucket type sprayer : It consists of a hand operated single or double acting pump which may be placed into any ordinary bucket containing spraying solution. Plunger rod is hollow and serves as the compression chamber. Liquid is discharged in both suction and delivery strokes, hence a continuous application can be made. One hand operates plunger, while another hand keeps the pump in stable position. This pump is mostly made of brass. It is very light and easily handled and develops sufficient pressure to spray small gardens and low trees. It develops a pressure of 4 -10 kg/cm2.
Duster is a machine to apply chemical in dust form. Dusters make use of air streams to carry pesticides in finely divided dry form on the plants. A duster essentially consists of: (a) hopper, (b) agitator, (c) feed control, (d) fan or blower and (e) delivery nozzle.


Power Sprayers
Types of dusters
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Plunger type hand duster: This machine consists of a chamber for the dust, outlet, a cylinder with piston, piston rod and handle. Sometimes the dust chamber is placed below the cylinder. By moving the piston back and forth in the cylinder, dust is forced through the outlet. This type of duster is suitable for dusting a small area.

Rotary type hand duster : This type of duster is provided with an enclosed fan geared to a hand crank and a hopper holding the dust. It is equipped with an agitator to stir the dust and a regulator to control the discharge opening. The duster is usually fastened to the operator by means of shoulder strips. The right hand is used for cranking and the left hand to guide the discharge tube. These dusters can hold about 3.6 to 4.5 kg of dust and are large enough to treat 0.4 to 0.6 hectare of cropped area in a day. Ordinarily they are not found suitable for dusting over 3 meters height.

Power duster : The power duster of small capacity is generally mounted on the back of the operator. It consists of cylindrical container, blower, high speed engine and discharge hose pipe. The cylindrical container is provided with two compartments, one for gasoline, and the other for the powder to be dusted. The blower is directly mounted on the crankshaft of the high speed (4000 rpm) air cooled engine. The air pressure is utilized to agitate the dust in the container in order to blow it through the flexible hose pipe. The direction of the dust is regulated by a movable delivery spout suitably fitted with the unit. The dust can be blown up to about 6 meters height. Such a duster can cover about a hectare in a day. This type of duster can be converted into a sprayer with little modifications. Portable type power dusters are also in use. They are mounted on two wheel trolleys.

Care and maintenance of dusters :

(i) Duster should be thoroughly cleaned before and after use with a suitable brush.
(ii) The hopper should be filled with dust about half of its capacity.
(iii) The lid of the hopper should be closed during the operation.
(iv) In rotary dusters, the handle should be cranked at 30 to 35 rpm for efficient performance.
(v) Before and after use of the duster, the dust from the fan box, suction pipe and hopper should be thoroughly blown out.
(vi) Pieces of paper, gunny bag and other foreign materials should be prevented from getting into the hopper.
(vii) The agitator parts and dust feed should be occasionally checked for blockage by foreign matter.


Power Duster

Sprayer