There is a great amount of interest, in using UAV/ and Drones for pesticide application in agriculture / horticulture. This is because of several reasons such as:
- Shortage of labour and equipment to cover large areas in a very short period of time to control pest and disease.
- Conventional spray equipment is expensive to own and operate
- Team of 1 to 2 persons are generally required to do conventional spray
- Conventional spray equipment is not suitable to spray tall trees or in difficult terrain such as mountain slopes.
- Conventional sprayers use high volume of water
- There is risk of exposure of toxic pesticide to spray operator
In contrast – spray Drones are thought to be modern, advanced and perceived to be more efficient, covering large areas in short time. It is felt that custom spraying operation using Drones would be a viable business model which will maximise use potential of high priced Drones.
Weather the Drones are performing pesticide application in satisfactory manner, giving at least equivalent performance of pest control, is not well studied. Commercial Drone manufacturers / operators, pesticide / fertilizer companies and entrepreneurs are seen to be promoting the use of Drones with proprietary pesticide / label claim extension products in the Indian market.
Government of India, Indian scientists, Agricultural universities and Pesticide / fertilizer giants have shown their commitment to promote application of pesticides through Drones without any proof of efficacy (% kill w.r.t conventional sprayers). For some unknown reason, in one stroke CIB&RC (India) has permitted the application of all registered pesticides in schedule through Drone application (although the label claim is for high volume spray). Whether any study was conducted to scientifically evaluate the efficacy of the Drone sprayers by Government of India before giving such permission is not known.
There are many reasons to doubt if Drone sprayers will provide satisfactory application of pesticide on row crop and fruit trees. The most obvious are:
Design of Drone sprayers: Look at the drawing / illustrations of 4 and 6 rotor Drones in different orientations given below:-
From the drawings / illustrations number 1 to 4, it can be seen
that:
- 1, 2 or 3 nozzles of the 4 or 6 nozzles used in a Drone are spraying the same area of the row twice. This is a waste of money and resources and could cause phytotoxicity, higher amount of pesticide residue on crop.
- Since most Drones are not using a boom, uniformity of coverage is questionable.
Drawing no 5 – shows how use of a boom fit below the Drones may provide a better coverage of a row swath width. Even for ground spray equipment the boom height / nozzle height above canopy has to be adjusted as per crop growth.
The swath width can be increased by using nozzles with wide angle, appropriate liquid pressure on a boom to spray from a particular height.
A. Drone manufacturers do
not share information about:
- Type and nozzle number used with the spray angle.
- Liquid pressure at nozzle
- Flow rate of nozzle (ml/minute)
- Swath width at particular height above canopy (Spray height)
- Droplet size - VMD (micron)
- Droplet coverage study in canopy
- Droplet deposition study within the canopy - : number of droplets per square inch on upper and lower side of leaf and percentage of droplet area to leaf area.
- Spray penetration into the canopy: by deposition study
- Water volume to be used / acre depending upon number of nozzles & crop density
- Flight speed of Drone (meter/second)
- Drift?
Authentic scientific studies / trials must be carried out to prove that particular model of Drone is able to provide good coverage, good deposition and good penetration within the canopy and provide users pest control efficiency comparable to conventional equipment.
Increasing the spray height causes small droplets to drift or to evaporate as they fall. In Drone spraying, one must take into account the droplet size (VMD) and type of nozzle to provide adequate swath width and coverage. Some Drone manufacturers claim droplet size between 50 to 400 micron (without mentioning VMD) and suggest 2.5 to 3 meter spray height, spray volume of 15 to 25 lit/Ha.
In the hot and dry Indian climate, small droplets of 50 micron falling from 3 meter height will drift and evaporate without coming in contact with the leaf canopy. If percentage of larger droplets of 150 to 400 micron is high, then it will not be possible to provide satisfactory coverage in 15 -25 lit/ ha. Larger droplets falling from 3 meter height will bounce off the leaf and shatter reducing effectiveness of spray.
It is reported that Government of India is subsidizing purchase of Drones. Some Indian Agricultural Universities have been given mandate to teach Drone pilots.
It is surprising that Indian Government, which requires all agricultural sprayers (even knapsack) to meet BIS specifications in order to obtain subsidy, is not asking Drone manufacturers relevant questions regarding the spray efficacy or specifications of their equipment and without any proven benefits allowing use of all pesticide through Drones. This could be a great disservice to non-technical gullible farmers who are looking at Drone spraying as a solution, since they are not able to organised numerous pesticide spray required on farm.
If you like the article in this series, then send the link of this article to others and also follow this blog.
If you have any queries/suggestions regarding the article, you can send us through the e-mail - ecoagropune@gmail.com.
This comment has been removed by the author.
ReplyDelete