Tag: wheat

  • Evaluating Wheat Head Coverage from Two New Nozzles

    Evaluating Wheat Head Coverage from Two New Nozzles

    We’ve written extensively about angled flat fan nozzles and their ideal operating parameters (i.e. pressure, boom height, droplet size, volume and travel speed) for spraying wheat heads. Generally, coverage on the sprayer-approach side of a wheat head (aka the advance side) is easier to achieve because droplets from a conventional flat fan geometry tend to follow a downward-forward vector. Imagine dropping a ball from the window of a moving car. An outside observer would see it travelling forward as it fell.

    The back of the wheat head (aka the retreat side) and the sides are harder to hit. When we introduce a rearward angle to coarser, fast-moving droplets, the high momentum and downward-rearward vector deposits spray on the retreat side of the wheat head after the sprayer passes over. Mythbusters produced a cool video segment that illustrates this concept by matching the rearward velocity of a soccer ball to the forward velocity of a truck; the ball falls straight down. Of course, in our case we want it to shoot backwards.

    A great deal of independent research has determined that low booms coupled with dual fans that produce coarser spray and higher volumes will optimize coverage on any vertical target. Asymmetrical nozzles that have a more aggressive rearward angle perform better still. Of course both of these claims assume a “reasonable” wind speed, because the finer droplets in the spray experience a comparatively lower degree of inertia. Inertia is a property of matter that describes the resistance of an object to changes in its state of motion and it’s related to the object’s mass. What this means is that smaller droplets slow quickly, are easily deflected by wind, and tend to deposit on the windward side of the wheat head.

    So, maybe you already knew all that. What’s new?

    Two asymmetrical tips have been introduced in recent years and we wanted to characterize their coverage (Figure 1).

    The first is the “Fusarium Fighter” which is a combo-tip developed by Nozzle Ninja in Stettler, Alberta. It combines Pentair Hypro’s FC-3D100 (a non-AI tip with a 2 star rating from LERAP and a 100° wide fan) with ASJ’s, Compact Fan Low-Drift Coarse with its 120° wide fan. The 3D already has a 55° angle from vertical and the twin cap brings that to a very steep 65°.

    The second is Pentair Hypro’s Asymmetric Ultra Lo-Drift AI Ceramic. This is the same as the Lechler IDTA where the front angle is 120° wide, angled 30° forward from vertical and sprays 60% of the spray volume. The rear fan is 90° wide, angled 50° back and sprays the remaining 40%.

    Finally, and only to illustrate how symmetrical fans and finer droplets are perhaps not ideal for reliable wheat head coverage, we ran TeeJet’s TwinJet Twin TJ60-110VS. This is two 110° flat fans and the angle between them is 60° (30° fore and 30° back from vertical).

    Figure1. Evaluating coverage from three nozzles in winter wheat.

    For each treatment, five nozzles were positioned mid-boom on a Deere 410R to minimize any turbulence from the sprayer wheels and chassis and to reduce the degree of yaw. Extensions were used on all tips to ensure the spray did not impact the boom itself. All other nozzles were turned off. Nozzle bodies were on 50 cm (20″) centres and positioned 50 cm (20″) above the average wheat head. Travel speeds were selected to achieve 187 L/ha (20 gpa) at a pressure ideal for the tip in question and this is recorded in Table 1. Contractors and other such custom applicators may find these speeds low and the volumes high, but in this study we chose to emulate usage in smaller operations. The effect of travel speed on coverage is debatable but likely quite minor. More can be found on the subject in this article.

    NozzleSpray QualitySpeed Pressure
    AULD-C 11003C6.6km/h (4.1mph)483kPa (70psi)
    FF (CFLD-C02 & FC3D11003)VC & M8km/h (5mph)207kPa (30psi)
    TJ60-11004F8km/h (5mph)207kPa (30psi)
    Table 1. Operating parameters for three nozzles applying 187 L/ha (20 gpa) to wheat heads.

    The weather was 25°C, 40% R.H. and there was a very light and consistent tail wind of 2-4 km/h (1.2-2.4 mph). These were ideal conditions because it was not hot or dry enough to evaporate finer spray appreciably, and not windy enough to deflect the spray.

    Water sensitive paper (Syngenta) was wrapped around the wheat head and held by a paper clip (see Figure 2). This gave a panoramic representation of coverage. Two more were mounted nearby on a length of rebar at wheat head-height; One faced the sprayer advance and one faced the retreat. Three such sets were positioned inline, spaced about 1 m apart and centered on the swath produced by the five nozzles. This was repeated 2x for each nozzle. Papers were retrieved, digitized and analyzed per the method described in this article.

    Figure 2. WSP wrapped around a wheat head.

    The resultant coverage is recorded in Table 2 and graphed in Figures 3 and 4.

    NozzlePanoramic:
    Area covered (%)
    & deposit Density (#/cm2)    		Advance:
    Area covered (%)
    & Deposit density (#/cm2)    		Retreat:
    Area covered (%)
    & Deposit density (#/cm2)
    AULD-C 1100310.2%
    130.4 deposits/cm2    		7.9 %
    56.1 deposits/cm2
    		11.1%
    87.7 deposits/cm2
    FF (CFLD-C02 & FC3D11003)13%
    97.5 deposits/cm2    		9.0%
    46.9 deposits /cm2    		18.3%
    72.4 deposits/cm2
    TJ60-1100422.3%
    471.0 deposits/cm2    		21.5%
    320.9 deposits/cm2    		11.4%
    286.1 deposits/cm2
    Table 2. Average coverage from three nozzles applying 187 L/ha (20 gpa).
    Figure 3. Comparison of average percent area covered for three nozzles.
    Figure 4. Comparison of average deposit density for three nozzles.

    Unless you are experienced with interpreting coverage data, these numbers and graphs may not convey what coverage truly looked like. And since we saw some unexpected results, we felt it would be best to digitize the papers from each nozzle and create graphics to support our observations and opinions on how they performed. Each image shows six replications of each orientation. We’ll begin with the AULD in Figure 5.

    The AULD was operated at a relatively high pressure to create the Coarse droplets recommended by the nozzle manufacturer. The steep rearward angle produced a higher degree of coverage on the retreat side compared to the advance. The streaky or tear-drop shaped deposits indicate a droplet that “scuffed” along the paper surface, almost but not quite in parallel. On the panoramic targets they tend to correspond with the sides of the paper, where the droplets are not aimed directly at the surface as in the “advance” and “retreat” surfaces. All in all, this nozzle performed well and created droplets large enough that we feel they would stay on course in a higher wind and not get tied up on the awns of the wheat head.

    Figure 5. Digital scans of water sensitive papers from the AULD nozzle. Spray quality was C.

    Next is the Fusarium Fighter. This nozzle was developed in Western Canada where, on average, sprayers tend to travel faster than they do in Ontario. Certainly this isn’t the case for all Ontario fields, but we chose to emulate usage in home farm operations where fields may be smaller and less level. This is relevant because faster travel speeds permit the use of a larger 3D nozzle to achieve 20 gpa, which in turn produces a coarser spray quality. In our trials, we traveled more slowly and that necessitated a smaller 3D that produced only a Medium droplet size. We hypothesized that those smaller droplets may not stay on course, but the papers show otherwise (Figure 6).

    Figure 6. Digital scans of water sensitive papers. Spray quality was VC and M.

    Coverage on the retreat side was very good and far outstripped the coverage on the advance side. In fact, the Very Coarse spray quality from the CFLD-C may be too large. Dropping from VC to C would create more droplets and a higher deposit density on the advance. We did see some gaps in the panoramic papers that likely reflect the lack of finer droplets which tend to move more erratically and contact the sides. Recall that we said weather conditions were ideal. It is still questionable how well a 3D producing a Medium spray quality would perform in windier conditions or on the boom ends where yaw tends to lift tips well above the ideal operating height.

    Figure 7. All three tips operating on a stationary sprayer at 40 psi. The Fusarium Fighters (foreground), the TwinJets (middle) and the AULDs in the background.

    Finally, the TwinJets (Figure 8). We used this nozzle only to demonstrate how the lack of an aggressive rearward angle and a Fine spray quality was not conducive to reliable wheat head coverage. Many studies have demonstrated that such a nozzle outperforms a single, conventional flat fan, but it is not the best choice of angled nozzles. Once again recall that these nozzles were positioned centre-boom where yaw and sprayer-induced turbulence were not an issue and in absolutely ideal environmental conditions.

    We saw tremendous coverage on the advance side and while we saw comparatively less on the retreat side, it still performed well compared to the other nozzles. The panoramic targets also indicated suitable coverage, both as percent area covered and deposit density. BUT, if we have some questions about how the Medium spray from the 3D would perform in more challenging conditions, we are far more concerned about the fines from this tip. Having used this nozzle in past demonstrations we are well aware of how non-uniform and erratic coverage can be, and that translates to poor efficacy and increased drift. However, sometimes circumstances conspire to create exceptions, and the coverage we saw in this trial is hard to fault.

    Figure 8. Digital scans of water sensitive papers. Spray quality was F.

    This trial was not intended to rank nozzles, but to explore the merits of a few new designs and evaluate their respective coverage. If anything the results reinforce the need to operate angled sprays correctly and in appropriate weather conditions. Water sensitive paper remains a quick and easy method for sprayer operators to evaluate their own coverage and inform any corrective actions to improve results in their own unique circumstances.

    Thanks to Dan and Paul Petker (Petker Farms) and Don Murdoch (Simcoe Research Station, University of Guelph) for providing the fields and operating the sprayers. Nozzle Ninja is gratefully acknowledged for the donation of AULD and Fusarium Fighter nozzles, and Spraying Systems Co. for the TwinJet nozzles and water sensitive paper.

  • Avoiding Skips from PWM Sprayers

    Avoiding Skips from PWM Sprayers

    Does this sound familiar?

    “This year was the first year we used a growth regulator on our wheat. After heading, we noticed a wavy pattern of different plant heights between 30 and 45° to the operating direction. It was only a couple inches difference and was difficult to photograph. We sprayed 12 gpa at 9 mph using TT11005 nozzles alternating forward and back at 35 psi and a 70% duty cycle. I’ve talked to other operators in Canada and in Europe and several customers have reported seeing this pattern, no matter which model of PWM sprayer. What’s happening?”

    Skips in cereal that are obvious to the eye can be difficult to photograph.

    The pulse width modulation is very likely responsible for the waves. We have a number of articles describing how PWM works, but here’s a brief recap of the relevant bits.

    A solenoid intermittently interrupts nozzle flow with a frequency between 10 and 100 times per second (depending on manufacturer). The proportion of the time the nozzle remains open is called the Duty Cycle. Each nozzle is linked to the neighbouring nozzles so that when one pulses on, the neighbour pulses off. So although you may only have half the nozzles spraying at any moment in time, sufficient overlap ensures there are no gaps in the pattern.

    However, depending on the combination of frequency and duty cycle, it is possible to lose that overlap between nozzles. This can cause a checkerboard pattern that appears to repeat in a diagonal line. The following two images are from www.Capstanag.com and they illustrate an ideal overlapping pattern and a pattern that creates skips.

    Here’s a 11008 at 10 gpa, 15 mph, 60% DC, 10 Hz, 21” boom.
    Here’s an 8008 tip at 5 gpa, 15 mph, 30% DC, 10 Hz, 21” boom.

    We can also sometimes see skips on the outer edges of sharp turns. In that case the outer boom section can be travelling two or three times as fast as the cab. In a conventional system, this would produce under-dosing in the outer region and over-dosing closer to the cab.

    Some degree of skipping may be more common than we realize. It’s only when we spray products that produce obvious visual symptoms at low doses that we can see a biological response. In the case of plant growth modifiers used to prevent lodging in cereals, we have a perfect storm situation. A region of reduced spray overlap, applied at a time when the crop is elongating rapidly, perhaps on rolling ground from an unstable boom height, can all conspire to create regions of reduced dose with striking visual symptoms.

    The following list describes conditions that can increase the potential for skips, and what you can do to avoid them.

    1. Low duty cycles. Cycles less than 60% should be avoided.
    2. Fast travel speeds. Faster speeds may help blend the spray in the swath a little, but too fast can create gaps and increase drift potential. At high travel speeds the system is usually operating at a high duty cycle unless an especially large nozzle size has been selected. Ideally, we want to run the duty cycle at 60-80%, but there are always exceptions. For example, according to Wilger, 90-92% is fine when you run at 20 gal/ac with their “15 gal tips”.
    3. Low booms. The lower the boom, the less overlap. Raising the boom to 24″ above the crop may help, but beware of drift.
    4. Narrow fan angles. Nozzle angles less than 110° reduce the degree of overlap and are less forgiving if the distance between nozzle and target decreases.
    5. Low pressure. Avoid operating at pressures below 35 PSI. Due to pressure drop at the solenoid, 40 PSI on the monitor might mean 28 PSI at the nozzle. Some nozzle tables account for solenoid-induced pressure drop and some do not. Low pressure may be insufficient to establish the full 110° pattern, and the resulting marginal overlap not only means inconsistent dose, but inconsistent droplet size because droplets are coarsest at the edge of the pattern. And, if that’s not already enough, note that air induction nozzles intended for use with PWM tend to create messy patterns at low pressures and low duty cycles.
    6. Especially coarse spray quality. Unless the label requires it, consider using spray qualities no larger than Very Coarse, particularly at low volumes. PWM frees the operator to use pressure independent of rate, so you may be able to accomplish this without swapping nozzles.
    7. Products that are highly dose-dependent. This one is likely unavoidable, but be aware they are the products most likely to produce obvious visual symptoms. In the case of PGR’s, we have not (yet?) seen any evidence that skips translate to reduced yield. Weed misses or sub-lethal doses of fungicide or insecticide might be another matter.
  • Wheat Head Coverage from Rotary Drones

    Wheat Head Coverage from Rotary Drones

    Editor’s Note: This work was performed in 2023. A more recent exploration into wheat head coverage was performed in 2025. This article is not obsolete as it introduces concepts and makes foundational observations. Read on, then read the 2025 article afterwards.

    Fusarium head blight is one of the most economically important diseases in winter wheat. Application timing is arguably the most critical aspect of effective crop protection. The application window stretches some two to five days following the point where 75% of the wheat heads are fully emerged and coinciding with the beginning of flowering (Figure 1). Product placement is the second most critical aspect, where the wheat head represents the primary target, and the flag and penultimate leaf are somewhat incidental, secondary targets.

    Figure 1. Winter wheat at T3 staging is optimal for fungicide application.

    This article describes the results of two experiments exploring wheat head spray coverage from a rotary drone. The first compares wheat head coverage from a drone to that of a helicopter (Figure 2). The second explores the effect of drone ground speed, and the related downwash, on wheat head coverage. All work was performed under PMRA research authorization. As of the date of this publication, there are no crop protection products permitted for application by RPAS in Canada.

    Figure 2. The helicopter spraying in background does not create a downwash. Note how the spray is not forced straight down but falls in a sheet subject to gravity and inertia. The rotary drone spraying in the foreground does create a downwash. Note how the wheat is displaced by the spray-laden air as the drone passes. At higher speeds, this downwash does adopt a down-and-back vector.

    Experimental Design

    Wheat field

    The wheat field was clay/loam located at 42°47’12.6″N 81°03’06.4″W near New Sarum, Ontario. Wheat was “common seed” planted on October 2nd, 2022, at 1.8 million seed/ac on 19 cm (7.5 in) row spacing. It was sprayed on June 5th, 2023, and at the time the wheat heads were about 0.7 m (2.5 ft) high.

    Treatments were laid out parallel with the planting direction in a randomized design. The helicopter pilot reported an effective swath width of 13.7 m (45 ft), which formed the basis for the treatment block widths (Figure 3). The helicopter made a single pass. The drone pilot reported an effective swath width of 4.5 m (14.75 ft). It made three passes per treatment block in the helicopter versus drone experiment but made only a single pass centred on the treatment block for the speed experiment.

    Both the helicopter and drone applied fungicide at label rate plus 0.125% Activate in a final volume of 50 L/ha (5 gpa). For the helicopter this was about 20 ac. per jug, and for the drone we created an equivalent tank mix using 450 ml fungicide and 37.75 ml Activate diluted with water to fill the 30 L spray tank.

    Figure 3. Treatment layout for both experiments. H: Helicopter. D: Drone. Yellow rectangles represent location of water sensitive papers on a 1.75 m (5.75 ft) spacing, centred on the treatment block. Flight paths were centred on the treatment block.

    Helicopter versus drone experiment

    For the helicopter treatments, five water sensitive papers (WSP) were spaced 1.75 m (5.75 ft) apart, centred on the treatment block. For the rotary drone passes, two rows of WSP were spaced 1.75 m (5.75 ft) apart, centred on the treatment block. Application volume was 50 L/ha (5 gpa)

    The helicopter had a 20 foot boom with CP-03-05 nozzles on 12” spacing, alternating between a 0.062 (smallest) orifice and a 0.172 (largest) orifice. Ground speed was 96.5 km/h (60 mph) and altitude ranged from 1.5-3 m (5-10 ft) above the wheat heads. The contractor company calibrated the helicopter according to their standard operating practices.

    The rotary drone was a DJI Agras T30 equipped with TeeJet TT110015’s. It flew at 5.1 m/s at 3 m above the wheat heads and applied three adjacent swaths of 4.5 m. The contractor company calibrated the drone according to their standard operating practices. A similar methodology can be found here.

    Drone speed experiment

    A single pass was made over three rows of WSP spaced 1.75 m apart, centred on the treatment block. The drone made two separate passes (n=2) for each speed. Samplers were retrieved and replaced after each pass and the same plot was used for all six passes. Application volume was 30 L/ha (3 gpa). Drone was refilled after every two passes to maintain a consistent weight.

    The rotary drone was a DJI Agras T40 programmed to apply an “Extra Coarse” spray quality at 3.5 m above the wheat heads with a swath width of 9 m. Ground speeds were 2 m/s, 4 m/s and 7.2 m/s and were visually confirmed by the RPAS controller. Once again, the contractor company calibrated the drone according to their standard operating practices.

    Target Locations

    For both experiments, SpotOn brand WSP from the same production run was pre-curled by wrapping it around a pencil, then wrapped around the wheat head and secured at the bottom by a small, spring back paper clip (Figure 4). This left approximately 1.5 x 1 inches (i.e. half) of the surface exposed to spray and provided an indication of panoramic coverage.

    The clip distorted the target by flattening it at the bottom and obscured a small portion of the target area, but this area was digitally removed during the analysis. By securing the WSP to the wheat head rather than a surrogate stake, the target moved naturally in the downwash of the drone. The papers were retrieved when dry, placed in individual plastic bags, flattened for scanning, and digitized using a DropScope within 24 hours of retrieval.

    Figure 4. Pre-curled water sensitive paper was wrapped around the bottom of the wheat head and secured with a spring back paper clip.

    Weather and Application Times

    Weather data was collected using a Kestrel 3550AG weather meter (Kestrel Instruments) in a vane mount positioned 1.5 m (5 ft) above the wheat heads. Wind speed fluctuated throughout the day, but wind direction remained relatively stable at 90 degrees to the flight path. Targets remained within the swath, despite any offset, as indicated by the consistent coverage observed on the windward WSP compared to other, downwind samplers in each pass.

    Application methodPass #TimeWindspeed (km/h)Temperature (°C)
    Helicopter18:452.017.0
    Helicopter210:004.517.7
    Helicopter310:204.819.9
    Agras T30110:204.819.9
    Agras T30210:455.219.7
    Agras T30311:008.620.0
    Agras T40112:258.221.6
    Agras T40213:004.822.4
    Agras T40313:305.222.8
    Wind direction remained a steady side wind (i.e. 90 degrees) to the flight path throughout day. Sky was clear (i.e. minimal to no cloud cover) throughout day.

    Results and Analysis

    WSP were scanned and digitized. Coverage was measured as percent surface covered (% area), and deposit density (# deposits/cm2). Given that only ½ of the WSP was exposed to spray, and the remining half was obscured during the wrapping process, the entire card was scanned, and the resulting coverage was doubled.

    Helicopter versus drone experiment

    For each helicopter pass, a single line of five WSP were averaged to a single data point. Therefore, n=3, but represents 15 WSP samplers. For the drone, two lines of three papers were placed in the block. Each line was averaged to a single data point, for n=2 per pass x 3 passes for a total of n=6, representing 18 WSP samplers. The following image (Figure 5) shows a digitized WSP typical of each method.

    Figure 5. Typical WSP from helicopter and drone applications at 5 gpa. Recall that only half the paper (the right half, in this case) was exposed following the wrapping process.

    The following histograms (Figure 6 and 7) illustrate the mean coverage for each application method, with standard error.

    Figure 6. Average wheat head coverage (percent area) by application method. Drone is n=6 and Helicopter is n=3. Bars represent standard error.
    Figure 7. Average wheat head coverage (deposit density) by application method. Drone is n=6 and Helicopter is n=3. Bars represent standard error.

    The drone covered an average 17% more surface area than the helicopter. The spray quality was visibly finer, as evidenced by the average 64% higher deposit count. As a matter of context, we ran a similar study four days later with a field sprayer running TeeJet AITTJ60’s on 38 cm (15 in) centres, 50 cm (20 in) above the wheat head. It applied 175 L/ha (19 gpa) compared to the 50 L/ha (5 gpa) applied by the helicopter and drone. The relative percent area covered is shown in Figure 8.

    Figure 8. Average wheat head coverage (percent area) by application method. Drone (5 gpa) is n=6, Helicopter (5 gpa) is n=3 and Field Sprayer (19 gpa) is n=6. Bars represent standard error.

    The more than fourfold difference in coverage from ground versus aerial application is significant, but given the relative concentrations of product applied (i.e. the same product rate) residue levels would likely prove equivalent for all treatments. Fungicide efficacy cannot be predicted from coverage data, but the convention is that the more surface area covered, the better the protection.

    Drone speed experiment

    The drone made two separate passes over each treatment block. For each drone pass, three lines of three WSP were placed in the block. Each line of three papers was averaged to create a single data point, for n=3 per pass and n=6 in total. The following histograms (Figures 9 and 10) illustrate the mean coverage for each application method, with standard error.

    Figure 9. Average wheat head coverage (percent area) by ground speed. Each speed is n=6. Bars represent standard error.
    Figure 10. Average wheat head coverage (deposit density) by ground speed. Each speed is n=6. Bars represent standard error.

    As an aside, note that the average is approximately 2% surface area for these 30 L/ha (3 gpa) applications compared to the 3.6% average at 50 L/ha (5 gpa) in the drove versus helicopter experiment, reflecting the results from many studies that show employing higher water volumes results in improved coverage until some point of diminishing return.

    The drone appeared to cover approximately the same surface area at all three speeds. However, when deposit density is considered, the slowest speed deposited 31% more droplets than the medium speed, which in turn deposited 23% more droplets than the fastest speed.

    One possibility is that higher speeds, which are known to create wider swaths, dispersed the spray over a larger area. Another possibility is that higher speeds, which are known to increase drift potential, left a greater proportion of droplets aloft, beyond the reach of the samplers. Yet another non-exclusive possibility is that deposit counts increased while overall surface coverage remained approximately equal because the diameter of the stain increased with speed. DropScope reports stain diameter, and this has been graphed alongside the deposit counts in Figure 11.

    Figure 11. Deposit counts share an inverse relationship with ground speed, but average stain diameter shares a direct relationship with ground speed.

    We see an inverse relationship between ground speed and deposit density, but a direct relationship between ground speed and stain diameter. This difference may appear small, but assuming stains are approximately circular, diameter can be used to calculate deposit area, per the following table.

    Drone Ground Speed (mph)Mean Coverage (%)Mean Deposit Density (#/cm2)Mean Stain Diameter (µm)*Mean Stain Area (µm2)
    4.52.088.4815,153.0
    92.261.388.36,124.0
    16.11.949.993.36,793.0
    *Assumes a circular deposit

    We see an increase in average deposit area of 16% and 10%, respectively, for each increase in speed. In previous trials conducted in corn in 2022 we saw a decrease in coverage and an increase in drift when drone ground speed was increased. We also observed that as the T40’s ground speed increased, the swath width appeared to increase. We did not measure effective swath width at different speeds, but if this observation is correct then droplet density by area would decrease at higher speeds. The loss of spray to drift and/or through increased swath width would explain why increased speed resulted in fewer deposits on the wheat heads.

    The increased deposit diameter is likely due to spread factor. Higher ground speeds would impart a higher droplet velocity and therefore cause droplets to spread more on impact. If this is the case, and had we conducted residue trials, we would predict an inverse relationship between ground speed and residue levels, despite having similar percent surface coverage. This observation underpins the importance of assessing deposition patterns as well as residue in coverage trials.

    Conclusions

    • For this use case, a drone applying 50 L/ha (5 gpa) produces a similar, if slightly higher, percent coverage on a wheat head compared to a helicopter applying the same volume. However, the deposit density is considerably higher.
    • Corroborating previous results in corn, drone application volume has a direct relationship with spray coverage.
    • For this use case, drone ground speed does not appear to affect the percent wheat head area covered, but there is an inverse relationship with deposit density. We theorize based on the direct relationship between ground speed and deposit spread, and prior evidence of increased drift with higher ground speed, that less active ingredient is deposited on the wheat head at higher ground speeds.
    • The relationship between downwash (i.e. dwell time, which is a function of downwash air energy and ground speed), wheat movement and coverage is unclear.

    Acknowledgements

    Thanks to Zimmer Air, Drone Spray Canada, Bayer Canada, Grower-Cooperator Adam Pfeffer and OMAFRA SEO student Vanessa Benitz.