It makes sense to use drones for spray applications – they can operate over sodden fields and tall crops where no machine could normally move, fly quickly to exact locations to treat target areas precisely, as well as be pre-programmed to navigate their own way around.
Recent equipment introductions, and regulation changes in particular, look likely to see aerial applications by UAVs to increase substantially and quickly around the globe.
Drone sales in the USA to rise by a third
In the USA sales are set to rise by a third in a year – probably thanks to new regulations that now permit drone applications. And, with John Deere showing its developments at the Agritechnica Show in 2019, it looks like drone spraying is moving into the mainstream.
In countries with advanced agriculture, aerial spraying by drone completes the precision farming virtuous circle. This begins with remote crop scouting targeting treatment areas that are followed by applications on a pre-programmed route. And this, can not only be achieved remotely, but also truly autonomously.
Massive benefits for farmers in countries with developing agriculture
Drone spray applications also provide massive benefits for farmers in countries with developing agriculture. Indeed, in countries like China and India, they have essentially enabled farmers to leap from hand-held applicators, skipping vehicle-mounted boomed machines, and going straight to drones. At the same time drones improve application timeliness, reduce the need for skilled labour and cut hand-held sprayer operators’ exposure to harmful pesticides.
Reducing overuse
Drones are playing a major role in the Chinese government’s aims to use advanced technology to modernise its agricultural production and help combat the overuse of chemicals in the country. A report by the FAO and World Bank shows the volume of pesticides it uses is three times more than the USA per hectare of land.
The latest developments in spray dronesChina uses three times the volume of pesticide/ha than the USA
XAG’s drone service has sprayed 20 million ha in China and 38 other countries
Drift wake from a UAV is randomised by the multiple rotors and their speeds
Lack of regulations slowing deployment of spraying drones
Elsewhere around the world the lack of regulations is slowing the wider deployment of spraying drones on farms. This is either due to rules not keeping up with technology or simple outright bans on all aerial applications – as in the whole of the EU. While many countries are catching up by including drone use in civil aviation law, the difficulty is compliance with spraying regulations. In many places chemical applications are tightly controlled and in most circumstances this will require changes to products’ registered use.
Drone applications will also have to comply with local regulations. For example, in the Netherlands all applications can only be made with 75% drift reducing nozzles or technology. Currently, in countries with advanced agriculture, ground-based application equipment developments and product use restrictions are focused squarely on reducing drift and increasing accuracy.
Drone spraying rules vary across the globe
The restrictions on use and strictness of regulations regarding spraying from drones vary around the world, according to the type of farming and whether countries have advanced or developing agriculture.
This is perfectly illustrated by the world’s three largest economies, the USA, EU and China. First the EU. In all member states aerial spray applications, including drones, are completely banned. There are discussions between farming and industry associations and governments, but most experts predict it’s unlikely the ban will be lifted in the near future.
In the USA drone spraying is now permitted in many states, provided pilots comply with strict Federal Aviation Administration operational rules as well as separate requirements for aerial applications.
In 2018, China introduced new regulations for commercial operations with drones weighing more than 25kg. Under the same regulations, for agricultural spray applications pilots will also require Class V – Crop Protection training.
A survey across Africa in 2016 found 73% of the 79 countries did not have any rules or regulations in place, 19% have some regulations, while the remaining 8% were formulating the rules.
Drones on target to deliver nutrients
Concerns about drift
There are questions about the quality, efficacy and safety of applications from drones and rising unease among researchers and experts in the more ‘traditional’ spraying community. It’s a concern shared by Tom Wolf, an independent spray expert from Canada, where pesticide applications from drones remains illegal. “My primary concern is around spray drift,” he explains. “Low drone payloads mean they are unable to carry much liquid, so by necessity they must use low application volumes to provide any sort of productivity.”
Drones expand to increase productivity
Size and carrying capacity of popular agricultural drones is definitely a limitation on output. But their dimensions are often determined by local regulations, with many countries granting varying degrees of ‘permission of operation’ depending on weight, often up to just 25kg.
For operators willing to invest in the necessary training and certification required for larger capacity UAVs, there is now a growing choice of heavy haulers. One recent example is from Tactical Robotics, an Israeli aerospace company partnering with crop protection company Adama to develop an agricultural version of its Cormorant. This drone has two internal rotors that enable vertical take-off and land and is powered by a 977hp engine. It has 500kg payload capacity (764kg including fuel) and can fly for 2.6 hours with a 300kg payload.
The only way to provide sufficient coverage with very low volumes is to use nozzles that produce finer droplets. “ASABE fine to very fine droplets will have problematic effects on off-target movement and evaporation. These fine droplets are also more prone to the aerodynamic eccentricities of aircraft,” he adds.
Failure to control movement of a spray is, and should be, a problem
Entering these finer sprays into the models to assess drift from applications from conventional, manned aircraft results in buffer zones that are hundreds of times wider. “Failure to control movement of a spray is, and should be, a problem,” he adds.
Research ongoing
While research into drone spraying is progressing, most of this relates to coverage and deposition as well as spraying speeds and heights. The USDA is, however, currently conducting trials looking at drift. Wolf is part of a working group in Canada researching drone applications, including drift analysis. While drones employ the latest, highest technology for flying, control and autonomous operation, some of the application technology is quite basic, particularly compared with modern vehicle-based boom sprayers. Drone manufacturers are addressing these issues with more sophisticated technology, such as rotary atomising nozzles, electro-static systems and other developments.
