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Four techniques applied during spraying of a pesticide
1:High volume spraying
The spray solution is prepared by mixing water with pesticide formulation in appropriate quantities. This diluted mixture is sprayed through hydraulic nozzles.
Almost all types of high volume sprayers have some kind of pump to supply pressurized spray liquid to the hydraulic nozzle which breaks the liquid into spray droplets .The high volume sprayers are operated manually or powered. E,g slide pump or hand sprayers, stirrup pump sprayer, compression sprayer, compression sprayer, lever operated knapsack sprayer etc.
2:Low volume spraying
The low volume spraying methods essentially reduce quantity of spray solution. Spraying as against 300 to 500 L/ha in H.V. spraying technique is reduced to 50 to 150 L/ha in L.V. spraying technique.
Motorised knapsack sprayer, also called Mist blower is a L.V. sprayer in which gaseous energy nozzle is used for fine breakup of spray liquid into fine spray droplets. The size of spray droplets depends upon:
1. Air velocity and volume
2. Liquid flow rate
3. Properties of spray liquid
3:Ultra low volume spraying
The ULV spraying is the method of pesticide application at minimum volume to
achieve economic pest control. In this technique of pesticide application the volume applied per hectare is less than 5 litres which is extremely low as compared to the conventional High Volume and Low Volume spraying methods.
The spray droplets in ULV spraying methods are very fine in size. Therefore, the
nozzles used in these methods are different. Various designs of rotory atomiser are used to generate droplets of 70 to 100 µ VMD.
4:Electrostatic spraying
The electrostatic spraying system reduces the application volume substantially and greatly improves pesticide deposits. The liquid atomisation is achieved by utilizing
electrostatic forces. The spray particles of about 50 µm size having high electrostatic charge are issued from the nozzle through induction or contact charging which creates ions of similar polarity to the liquid droplets which become electrically charged.
The application volume is drastically reduced to 0.5 to 1.0 L/ha besides much improved deposition of pesticide. The charged droplets leaving the nozzle repel each other owing to similar charge and thereby forming spray cloud.
Frederick paul answered the question on March 21, 2019 at 08:11
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