Spray drones for precision agriculture & conservation land management

It’s very easy as your career progresses to get so immersed in what you know that you forget that the knowledge isn’t actually widely known. And things that seem ridiculously obvious – aren’t, to other people.

This train of thought was precipitated by the polarised responses to someone else’s LinkedIn post regarding a new spray drone being developed.  Some people enthusiastically saw a potential solution, while others only saw a conga-line of problems. I’m a natural cynic and not impressed by anything new unless genuine benefits are clear. But I was astonished by the degree of negativity and lack of vision from people who theoretically have agricultural experience.

There’s absolutely no doubt: spray drones will revolutionise global land management. In response to the naysayers – of course chemicals must only be applied by trained operators, and when it comes to aerial application of chemicals, operators must be officially licenced. This is already the case in Australia and many other countries, where the aerial application of chemicals has been undertaken via planes and helicopters for many decades.  Operators have to have professional aviation qualifications plus chemical handling training. No country that values food standards would permit someone to buy a drone and chemicals and head off to do spraying, without government-sanctioned training and licencing beforehand.

So what is special about spray drones, vs manned aircraft?

Manned aircraft are still the best option for blanket spraying large areas – relatively quickly and cost effectively. (This may change in future – but it would be many years off.)

Spray drones come into their own:

  • Precision agriculture: precise spot-spraying of plants that have been mapped (via another drone, although satellite imagery may be sufficiently detailed and timely enough in future). This means less chemicals used; thus saving money and better for the environment. Weeds that were previously uneconomic to poison, due to their scattered nature, can now be treated.
  • Close to sensitive areas (other crops and beneficial insects such as bees), water courses and human habitation – drones can be very precisely, safely, efficiently and economically operated.
  • Waterlogged areas that cannot be accessed by ground equipment and too small for manned aircraft to treat. And the use of spray drones means no soil compaction.
  • Rough/inaccessible terrain – rocky, steep, densely vegetated – drones are perfect for spot treating areas that cannot be treated on foot; or with manned aircraft due to the layout of what needs treating or proximity of powerlines or other aviation hazards.  Weeds often flourish in hard-to-access pockets and seeds then spread back to treated areas (via the wind, water or animal/bird transportation). Also – some inaccessible areas have a higher conservation value than surrounding more accessible areas because of their inaccessibility, so there’s great value in being able to reduce weed infestations there.
  • Where there is the risk of ground machinery spreading serious weed seeds, pests and diseases within the area being treated.  (Banana diseases spring to mind.)
  • Timeliness. One of the main advantages of drones over manned aircraft is convenience – they can be put up in the air within minutes and address a small problem immediately, before it grows and becomes an expensive headache. ‘A stitch in time saves nine’ is one of the main benefits of using drones on farms and cattle stations.

Copious research has been undertaken by many different drone manufacturers and by university researchers around the world. In particular – China, Japan, South Korea, United States and Australia.  The best of this research work is gathered together at one event each year – the Aerial Precision Agriculture conference attached to the World UAV Federation’s annual congress in Shenzhen, home to nearly 300 drone manufacturers.

WUAVF Drone World Congress in Shenzhen, China – precision agricultural aviation summary by Professor Lan. The World UAV Federation’s annual conference gathers together many of the top drone researchers from around the world.

Spray drone research topics particularly relate to minimising spray drift and maximising effectiveness:

  • Nozzle design & optimum droplet size for different conditions and treatments (fine droplets are of course not wanted, as they are more prone to drift)
  • Spray rates
  • Speed and height of flight
  • Wind influence on spray patterns
  • Downwash/downdraft effects on spray distribution (used correctly, it’s an asset to ensure thorough target coverage)
  • Differing flight paths and methods for treating different plants, eg fruit trees vs open pasture

Aerial application associations for manned aircraft:

Chemical application pilots have actively campaigned against the use of spray drones. One of the complaints within Australia is that there is the risk of environmental contamination due to spillage when filling the drone and when cleaning it out. This is bizarre, given that farmers already use chemicals in ground machinery and in vastly greater quantities than the average spray drone carries; and aerial applicators of chemicals have to be trained and certified. This negativity from the manned aviation industry is unfortunate because spray drones in a country such as Australia are complementary to the work manned aircraft do, rather than competing. The smartest operators in the aerial application business have recognised this and are purchasing spray drones to complement the work they’re already doing with manned aircraft – while the rest spend all their energy saying it won’t work.

Ultimately – it always boils down to just using the best tool for the job. Spray drones won’t slice bread for you but they are a unique tool that will eventually become part of the furniture, globally. Spray drones used for precision spraying by fully trained and certified operators will greatly improve the world’s management of weeds, with immense agricultural and environmental benefits.

*Note – this summary was written in August 2020 but it will be expanded in future and links to related blog posts added. Drone blog posts are based on attending numerous events around the world, a great deal of online research, many hours of drone flight time and visiting other operators.  These blog posts are created to provide accurate and comprehensive global-standard information that is not available elsewhere.

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