Tag: drone

  • Drone Sprayers – Are we Ready?

    Drone Sprayers – Are we Ready?

    One of the fastest moving new agricultural technologies is spray drones. Hardly a month goes by without some sort of new capability, some new features. It’s truly an exciting space to watch.

    As with all things, there are good news and bad news to share. First the good news.

    Drone capacity is on the rise. The early drones shipped with hoppers of 8 to 10 litres. Part of the reason was to keep weight below 25 kg. Below this weight, pilot licensing requirements and flight restrictions are easier. Anyone with a Basic RPAS license (RPAS is the official term for drones, Remotely Piloted Aircraft Systems) can operate drones up to 25 kg. Above this weight, one requires an Advanced license, which is much more difficult to obtain. Current drones like the DJI T40 have a hopper capacity of 40 L, allowing more area to be covered per flight.

    The new DJI T40 holds 40 L of liquid and has a claimed swath width of 36 feet (Source: DJI)

    Swath widths are increasing with drone size. The limiting factor for electric drones is still battery power. Flight times of 15 to 20 minutes are possible, depending on the ferrying distance. As a result, larger drones don’t necessarily fly longer, but they spray wider, up to a claimed 30 feet for the DJI T30, and 36 feet for the T40.

    Atomizers are improving. The trusty flat fan nozzle certainly works on a drone, but its proper operation depends on spray pressure. And spray pressure is not currently reported by drones. Instead, their application software relies on flow rate, and pressure is adjusted in the background in response to changes in travel speed, swath width, or nozzle size. Although drone flow meters are remarkably accurate, the operator could inadvertently operate the drone at a pressure that produces the wrong spray quality for the conditions.

    Enter the rotary atomizer. Long a darling of the thinking applicator, these atomizers use centrifugal energy to create a spray with a tighter span, meaning fewer fine and fewer large droplets. Spray quality still depends on pressure-generated flow rate, but droplet size can additionally be altered with rotation speed. This means that if a faster travel speed increases the spray pressure, the effect on spray quality can be counteracted with a changed rotational speed to keep everything more uniform.

    Rotary atomizers, like this one from XAG generate more uniform droplet sizes and can alter droplet size without changing spray pressure.

    Hybrid systems are entering the market. Rotary wings allow for precise positioning of aircraft and they provide downwash that helps spread the spray pattern out. Downwash also improves canopy penetration and could reduce drift, like air-assist, if used properly. But rotary wings use a lot of energy, limiting battery life. When flown at the wrong height or speed, deposit patterns, drift, and swath width will change. That has to be managed and requires experience.

    In comparison, hybrid drones have fixed wings for flight and rotary wings for take-off and landing. The rotors just rotate into the position needed at the time. Fixed wing drones will fly faster, possibly improving capacity and also reducing the effect of the downwash. These systems are new, and much needs to be learned before we understand their various characteristics. But they offer a nice avenue into more productivity.

    Hybrid drones like this one from Advanced Robotics can cover more ground with less turbulence than a rotary wing drone.

    Drones are multi-purpose. Virtually all drones have interchangeable wet and dry hoppers so they can be used to apply dry nutrients or seed as needed. That makes them quite versatile. But the newest spray drones have scouting-quality cameras on board and can be asked to take high resolution images while they’re spraying. At the end of the mission, a very detailed picture of the crop emerges, with much higher resolution than the higher-elevation scouts produce. Other sensors on the drones can be used for variable rate application of nutrients, or even for spot spraying weed patches.

    Scouting camera takes pictures while conducting a spray mission (Source: DJI)

    Now for the bad news. It’s still not legal to apply mainstream pesticides using drones in Canada, and it may stay that way for a while yet.

    Pesticide application by drones remains illegal in Canada. The main reason is that the Pest Management Regulatory Agency (PMRA) has declared drones to be unique application method, separate from ground sprays and aerial sprays from piloted aircraft. This has triggered the need for risk assessment data for spray drift, efficacy, bystander exposure, crop residue. It’s a fair decision – drones produce finer sprays than any other existing system, they potentially use lower water volumes by necessity, and they create a less predictable deposit due to rotor downwash. The majority of current pesticide formulations are designed for 5 to 10 gpa, this creates a certain concentration of surfactants and products that interact with plant surfaces or that change the potency of drift. Altering this by a factor of 5 can have undesirable outcomes. Yes, aircraft also use lower volumes, but more in the area of 2 to 5 gpa. Drones could cut that in half again, and that warrants study.

    Registrants haven’t rushed to study drones. Most major manufacturers of pesticides have a small drone program to get their feet wet, and most have applied for Research Authorization (RA) from the PMRA to study them. But the decision to register a drone use for a pesticide has much to consider. Is it worth it to generate the required dataset for the regulators? Will drones amount to a lucrative new market for product? Do we have the resources and expertise to service this new market? The answers to such questions are clearly complex and much remains unknown. The registrants’ caution is understandable.

    There may be a small portfolio of available products. Anyone thinking that a fleet of inexpensive, nimble drones will replace their ground sprayer is banking on the registration of the products they need in their operatioin by the registrants. The most likely products to be registered are fungicides, for which drones would offer several advantages in canopy penetration and spraying in tight time windows due to, say, wet weather.

    Another obvious use is in industrial vegetation management where rough terrain or remote locations make it difficult to use wheeled sprayers. Or vector control with larvicides, which, incidentally, comprise the first pesticide registrations for drones in Canada (two microbial mosquito larvicides were approved for drone use in October 2022).

    But it seems unlikely in the short term that a producer would have their pick of products to apply by drone anytime soon. And this means that a drone would remain a supplemental tool on the farm, not the main workhorse.

    Regulatory hurdles are substantial. Not only is a pilot required to be licensed to use drones, a pesticide application also requires a Specialized Flight Operations Certificate (SFOC). In general, SFOCs are required if:

    • you are a foreign operator (i.e., not a Canadian citizen or permanent resident);
    • you want to fly at a special aviation event or an advertised event;
    • you want to fly closer to a military airport;
    • you want to fly your drone beyond visual line-of-sight;
    • your drone weighs over 25 kg;
    • you want to fly your drone at higher altitudes;
    • you want to fly your drone carrying dangerous or hazardous payloads (e.g. chemicals);
    • you want to fly more than five drones at the same time.

    SFOC applications are fairly easy to fill out. Aside from identifying the drone and the pilot, the application needs the purpose of the mission, the location of the mission, and the time period of the mission. The problem is that it may take up to 30 days to hear back for simple missions, 60 days for complex mission. And if the SFOC is not granted, you can’t fly. You can’t decide to spray a field at the last minute.

    The news is clearly a mixed bag. We have it all – exciting technology, obvious niche in the marketplace, significant regulations, slow process. In the meantime, spray drones are legal to purchase and relatively inexpensive. And we know they are being purchased. Canada doesn’t have a strong compliance system within the PMRA, so it’s hard to know how much pesticide spraying is being done illegally, or how perpetrators will be treated by the law.

    The reputation of the industry once again rests with hope that good decisions are being made by conscientious individuals.

  • The Most Important Developments in Spraying

    The Most Important Developments in Spraying

    Some things have improved a lot. Others have lost ground.

    Some years ago, a few of us weed scientists sat around a table and debated the most important developments in agriculture in our lifetimes. It was a great discussion, and we arrived at a few that included direct seeding (for its soil and moisture conservation as well as improved fertilizer placement), GMO crops (for slowing Group 1 and 2 herbicide resistance), and the abandonment of summer fallow in much of western Canada. Let’s apply this exercise to spray application to see what we come up with.

    What follows are my version of the most important spray technology developments in the last 50 years.

    1. Low-drift Nozzles. Spray drift is the biggest time management challenge and also perhaps the biggest public relations battle. These nozzles reduce drift, making more time available for spraying and doing it safely and effectively.
    2. Rate Controllers. I both love and hate these things. On the one hand, a rate controller matches sprayer output to travel speed. On the other, it has allowed spray pressures to go wherever they need, even beyond the optimum, to match travel speed, and that can lead to nozzle performance issues.
    3. Pulse Width Modulation. The pulsing nozzle fixes the rate controller problem mentioned above. Now, travel speed and pressure are independent. Plus, of course, a whole host of other flow management options, such as turn compensation and rate boosting, become available.
    4. Optical Spot Spraying. Once you see these in action, you can’t go back. Why would you spray a whole field when weeds only cover 10% of it? Products like WEEDit and WeedSeeker are proven green-on-brown performers after years of field success around the world.
    5. GPS Guidance. Some of us grew up with foam or disk markers, others learned to aim for brave family members perched on headlands. Achieving accuracy was stressful, overlap was insurance, and misses were common. The importance of this development is probably under-estimated.
    6. Sectional Control. The ability to adjust the spray width in individual nozzle steps makes sense, and this can come with or without PWM. In fact, that alone can save 5% of an annual chemical bill compared to conventional sections measuring about 10 to 15 feet. And it’s definitely better than the left boom or right boom options from the 70 and 80s.
    7. Operator Comfort and Safety. The refuge of the cab makes longer days bearable for all equipment, but for spraying it dramatically improves safety as well.

    But we’re far from done. We still need work in these areas.

    1. Cleaning and Waste Management. I can’t imagine another industry where managing potentially hazardous leftover materials are left to the discretion and circumstances of the applicator. Let’s make it easy and fast to thoroughly clean the sprayer and safely dispose of leftovers. Step 1 is smarter and simpler plumbing.
    2. Boom Stability. Booms are too high, resulting in more drift and poorer nozzle performance, and adding to operator stress. The sole reason is unsatisfactory levelling. It’s possible to solve this, but it seems to not be a priority.
    3. Weight. The road to productivity seems to be paved with larger, heavier machines. The side effects are fuel consumption, compaction, getting stuck. Let’s get smarter with frame design and logistics and talk acres/h rather than tank capacity and power.
    4. Cost. All farm equipment has seen cost increases that far outstrip inflation or any reasonable accounting of productivity and features. Sprayers lead the way. Yes, it’s possible to spins this as a value proposition. But it shouldn’t be necessary.
    5. Drift Management. Sprayer design continues to ignore drift management. We need sprayers that produce less drift by design, and this requires consideration of tractor unit, wheel, and boom aerodynamics. It’s more than a droplet size issue.
    6. Direct Injection. Although very handy for single product application, the plethora of product formulations and mixes has limited the success of direct injection systems. The complexity of injecting at the nozzle, and the resulting lack of available systems, has stymied some very attractive options, such as site-specific rate or product use.
    7. Ergonomics. If you need training, or to call someone before using your new sprayer for the first time, something’s wrong. Interfaces need to be intuitive and simple. The golden age of spray monitors was the 1980s. Those featured a main power toggle switch, a pump power switch, boom section switches, an agitation switch, and a simple way to enter the important information which was basically desired application volume. The screen can still be pretty, and you can still paint and monitor or tweak all the functions if you like that. But let’s at least have different tiers so beginners can also use the machine. Make interfaces using the philosophy Steve Jobs instilled in his trusted designer Jony Ive with the first iPod: no more than three clicks to achieve any desired outcome.

    A few areas show promise and may suit certain niches.

    1. In-Crop Weed Sensing. The green-on-green sensing that has been made possible by machine learning has shown some encouraging early success. Continuing improvements will eventually bring its reliability to within commercially acceptable standards. There is significant activity below the radar in this area, as all players recognize the enormous upside of a breakthrough.
    2. Autonomy. While dispensing a pesticide adjacent to sensitive areas isn’t exactly the low-hanging fruit of autonomy, such field sprayers will have a fit in the temperate plains of North and South America, Australia, and Asia and may help solve the cost and weight problem.
    3. Drone Application. The rapid pace of advancement in remotely piloted aerial systems, along with a seemingly low barrier to entry of new companies, will put pressure on the industry to make a decision on this alternate application method. If it can be done safely, it will have a dramatic impact.

    If you want to improve your sprayer, don’t ignore the small things you can do in your operation. Although we’re conditioned to look for game-changing technology, the most sustained improvements don’t come from a single innovation, but from a period of persistent evolution. A lot of small improvements add up. Spray application is no different.

  • The Challenges of Spraying by Drone

    The Challenges of Spraying by Drone

    Spray application by drone is here. It’s common practice in South East Asia, with a very significant proportion of ag areas now treated that way. Estimates from South Korea, for example, suggest about 30% of their ag area being sprayed by drone. It’s in the US, too. The Yamaha RMax and Fazer helicopters, which pioneered drone spraying in Japan dating back to the mid 1990s, have been approved for use in California since 2015.  DJI, the world’s largest drone manufacturer, introduced their ag model, the Agras MG-1, to North America in 2016. Many other spray drones are available or in development.

    As William Gibson, the author of Johnny Mnemonic, once said, “The future’s here, it’s just not widely distributed yet.”

    DJI Agras MG-1 spray drone (Source: DJI.com)

    Proponents of drone spraying cite a drone’s ability to access areas where topography is a problem, such as steep slopes, where productivity of manual application is much lower, or low areas where soil moisture prevents ground vehicles. Operator exposure is reduced compared to handheld application.

    Opponents talk about productivity and cost factors compared to manned aerial application, spray drift, and rogue use.

    Before drone spraying becomes commonplace, two important things need to happen.

    1. Federal laws need to be updated to accommodate the unique features of remotely piloted aircraft systems (RPAS), as they’re now called. Current laws make many assumptions unique to manned ships, and the process to correct that will require some patience. A thorough review for US laws, and their shortcomings, can be found here.
    2. Federal pesticide labels need to permit the use of drones for application. As of August, 2021, Canadian labels have no such registered use.

    There is no doubt that we need to prepare for a future that includes spraying by drones. Features such as topography adjustment for height consistency and autonomous swath control are already essentially standard, and the capabilities that improve control and safety will continue to develop.

    And yet I’ve been nervous about the prospect of pesticide application with drones. My primary concern is around – you guessed it – spray drift. Because a drone payload is relatively small (about 5 to 25 L, depending on the model), application volumes will need to be low to have any sort of productivity. How low? For manned aircraft with a 200 to 600 gallon hopper, 2 to 4 US gpa (18 to 36 L/ha) are the lowest commonplace volumes. The lower volumes require a Medium spray quality (among the finer sprays in modern boom spray practice) to achieve the required coverage.

    It’s a simple concept: the less water is used, the smaller the droplets need to be to provide the necessary droplet density on the target. Drift control with coarser sprays requires higher volumes, and true droplet-size-based low-drift spraying can’t really happen at volumes less then, say 5 to 7 US gpa.

    At 2 to 4 US gpa, a drone would be able to do perhaps 1 acre per load. While OK for spot spraying, it represents a serious productivity constraint for anything larger.  There will be a push toward lower volumes, perhaps 0.5 to 1 gpa (5 to 10 L/ha). The only way these will provide sufficient coverage is with finer sprays, ASABE Fine to Very Fine, with expected problematic effects on off-target movement and evaporation. These fine droplets are also more prone to the aerodynamic eccentricities of aircraft.

    Vortices from the rotor can create unpredictable droplet movement (Source: kasetforward.com)

    The current regulatory models for aerial drift assessment in North America, AgDISP and AgDRIFT, are not yet able to simulate drone application. But by entering finer sprays into these models for their conventional manned rotary wing aircraft, we can see that buffer zones will be higher. Much higher. And that outcome will give pause to regulators. Failure to control the movement of a spray is, and should be, a problem.

    Estimated Buffer Zones (calculated by AgDISP) for a reference rotary wing spray aircraft, using three pesticide toxicologies and two spray qualities.

    Furthermore, ultra-low volume (ULV) sprays can change the efficacy of some products, and these will require new performance studies. At this time, regulators are seeking information not just on spray drift, but on product efficacy, operator and bystander exposure, and crop residues.

    Regulators are currently collecting spray drift and efficacy data from drones. Since the drones available in today’s market do not conform to a common design standard like fixed or rotary winged manned aircraft, each model may have its own characteristics and need its own study. Some will have rotary atomizers, others will use hollow cone hydraulic sprays. Some will have electrostatic charging, others may propose special adjuvants.

    Once data are assessed, there will likely be restrictions in flight height, flight speed, wind speed, spray quality, water volume, perhaps air temperature and relative humidity (or Delta T). This is not new to spraying, as current labels already constrain use for both ground and aerial spray application, more so for aerial.

    The obvious question is how these proper application practices can possibly be assured. Operators will need more than just regulatory approval to use a drone, they will require proper training, similar to what a commercial aerial applicator now receives prior to operating a business.

    Recall that our aerial applicators are governed by national organizations, the NAAA in the US and the CAAA in Canada. These organizations are in regular contact with federal regulators to assure compliance. They also help fund research into application efficacy and safety. They organize conferences in the off-season and calibration clinics in the growing season. At these, flow rates are confirmed and deposited droplet size is measured. Spray pattern uniformity is assessed and corrected as necessary.

    Should drone applications be exempt from these controls? I don’t think that would be wise. Are we ready to implement them? Absolutely not.

    These requirements would change the drones’ economic model. And despite these precautions, a drone may still leave the control of a pilot due to unforeseen technical or human events.

    In the US, Yamaha does not sell their drone helicopters. Instead, they deploy their own teams to make the applications. This way, they have assurance that only trained and experienced pilots use the technology.

    As the industry gears up for the first registrations, we see drone service companies take a leading role in testing. Much is being learned via legal applications of liquid micronutrients, for example, or limited use of pesticides under approved research permits. And I’m pleased to see the recognition of drift management in these efforts through the use of low-drift nozzles. We are off to a promising start.

    Requests for drone use are in progress at our regulatory agencies. The outcomes of their risk assessments will provide important initial guidance, and food for thought and discussion. In the meantime, the drone development continues at a rapid pace, with new features and greater capacity at each iteration.