We were long overdue for a new classic rock parody, so we decided to re-tackle one of the greatest rock ballads ever written. With the ongoing success of drop pipes (aka drop arms, drop legs, etc.) in corn, we’re promoting directed spraying in verse.
If you’d like to read more about the research, check out this article, and this one too. Farmtario also wrote a nice summary from one of our 2022 demos.
So, this was a tough one, but we feel good about how we laminated a new message over Zeppelin’s tricky cadence and rhymes. It helps if you play the actual song as you read. Rock on:
There’s a grower who’s sure all corn glitters like gold and he’s spraying from seven to seven.
When he’s done, then he knows that the products he chose will handle the pests that he sprayed for.
Ooh ooh ooh ooh ooh And he’s spraying from seven to seven.
He sees signs on them all but he wants to be sure ‘cause he knows bug poop means that they’re feeding.
So, he stops for a look spits and wipes as he should sometimes all of his thoughts are misgivings.
Ooh, it makes him wonder Ooh, it makes him wonder
There’s a feeling he gets when the silks seem too wet and his scouting is slowly revealing.
In his fields he has seen in the irrigation rings that tarspot’s in the plot where he’s standing.
Ooh, it makes him wonder Ooh, it really makes him wonder
Maybe he sprayed the corn too soon Or too late, it could be too ‘cause the timing defies common reason.
And he goes back in the dawn to see what else has gone wrong and his checks echo pests that he’s after.
Oh whoa-whoa-whoa, oh-oh
If there’s cutworm in your corn row, don’t be alarmed now. It may have been coverage or timing.
But there’s a new way, you can spray now, and in the long run there’s time to change the for the next season.
And it makes him wonder Oh, whoa
Overhead spraying is a no-go in case you don’t know drop pipes are calling you to try them.
Diseases come in when the wind blows but did you know drop pipes cover stalks from end-to-end.
So, as you drive on down the row overhead spray just won’t go deep into targets, we all know are hard to hit deep down below.
Next year he can still have gold. Using drop pipes isn’t hard. Coverage will come to him at last.
Quick to mount, one and all, yeah They barely rock as sprayers roll.
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 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.
No matter where you live, it’s been a long time since the last “normal” ag trade show. The pandemic forced a break in this long-standing tradition, and it wasn’t easy. Trade shows are an integral part of doing farm business. At a time when there are fewer equipment dealers offering a lower diversity of makes, a trade show may be the only place to see and thoroughly inspect what other manufacturers offer. With that in mind, I spent a full three days at the 2022 Ag in Motion Show near Langham, Sask. to see the sights.
On the sprayer front, a lot has happened in the last few years. The strength within the “new kids on the block,” the Netherlands’ Agrifac sprayer and Germany’s Horsch Leeb, is noteworthy. Even with fledgling dealer networks, they’ve managed to sell dozens of units based on the strength of convincing features. These go beyond exceptionally wide booms and large tanks, and include smart plumbing designs with recirculating booms and easier cleanout. They also weigh less than their North American counterparts despite standard features like four-wheel steering and superior boom stability. Most importantly, both manufacturers are committed to innovation and offer quick iterations within their models, incorporating new ideas constantly. Often, it’s the small thoughtful things that save time and create endearment.
The Horsch-Leeb sprayer
Case IH showed their new generation 4450 series sprayer. The machine has many improvements over the 4440 edition, focusing on operator comfort, digital integration and hydraulic capabilities. It weighs more than its predecessor, as to be expected. The Millennium spray boom is great, but unfortunately, there is no factory-designed recirculation, leaving owners to go to the after-market for solutions–a missed opportunity.
The Case 4450 with Millennium boom
Since acquiring Miller Sprayers in 2014, New Holland has had a unique front-mount boom design, and one was on display. Nicely engineered, I’ve always liked the concept of a front-mounted boom for better visibility of the things that matter. But again, there’s no recirculation. Did they consider it yet feel it wasn’t a high priority? We know that recirculating booms perform a waste-free prime while avoiding cleanout problems with boom-ends. These are important issues for applicators. I’m also curious why NH hasn’t gone to the Wilger boom components and nozzle bodies for IntelliSpray, since the Wilger tips are still the best choice for PWM.
Front-mounted boom on New Holland SP410F
John Deere’s newly named sprayers were at the show, the new models also offering improvements in operator comfort. The one on display was fitted with its recirculating boom, a nice addition to the feature set. Like the Raven retrofit kit, it appears to be designed with 200 gpm flow needs in mind, necessitating additional pipes and hoses that other systems avoid. Such high flows are very rarely needed except for 28-0-0 topdressing. Still, kudos for having a factory installed, controller integrated option.
AGCO showed off its Fendt Rogator and my heart went pitter patter as I approached it, recalling seeing its namesake at Agritechnica 2019. At the time, I felt it was one of the top sprayers at the German show owing to its innovative frame and suspension systems (independent wishbone), unique pump system (centrifugal pump that can run dry and never lose prime) and efficient plumbing. But this Fendt Rogator was a traditional Rogator frame with a Fendt tractor hood and cab to fool the passer-by. It’s no slouch, with optional four-wheel steering, adjustable clearance, and Liquid Logic recirculating booms. I felt cheated, nonetheless.
Fendt Rogator, sort of.
A visit to the Apache display showed why they remain a valid sprayer option. Built on mechanical two-wheel drive, they save weight and have better fuel economy than their hydrostatic counterparts. Yet, they still offer large tanks and aluminum Pommier booms when requested. Like most other brands, Pulse-width Modulation (PWM) is an available option. Personally, my soft spot for lighter sprayers is due to analysis of logistical efficiency–fill, clean and transport times. These create competent productivity values even with smaller sprayers that are more affordable to own and operate.
Light and nible Apache with strong Pommier aluminum boom
That led me to PhiBer Industries, creators of the DASH tender system. The family-owned firm from Crystal City, Man. creates custom solutions for hauling water and metering pesticides to sprayers. Thoughtful designs and use of air-driven product pumps with volumetric metering creates an efficient system that’s easy to understand and use. PhiBer joins existing products from Pattison Liquid, Free-Form Plastics or The Handler to offer a basic inductor and pump system. They will also build a complete custom trailer incorporating numerous additional features.
Phiber DASH tender system
Weed detection was shown by three exhibitors, but only one demonstrated it in action. Croplands had its field-proven green-on-brown WEEDit unit installed unit on a customer’s John Deere R4045, available for a test drive, as well as offering technical support at a booth. WEEDit remains the standard for green-on-brown and works very reliably out of the box. John Deere had an installed See & Spray Select, also green-on-brown, on a sprayer, but did not run it.
The most exciting new item sat at the Agrifac booth with their AiCPlus feature courtesy of Bilberry. Bilberry is a small French company, recently acquired by Trimble, selling green-on-green spot spray retrofits in Australia for over a year now. In Canada, they offer four algorithms at this time: green on brown for general burndown or desiccation; green-on-green for broadleaf weeds in cereals; grassy weeds in canola; and, both broadleaf and grassy weeds in corn. Powered by colour cameras and NVIDIA processors, continuous advancements in the software will improve performance as more weeds are added to its list of capabilities. Two AICPlus machines are running in Manitoba, and it’s good to see the company focusing on this market. John Deere and Greeneye, for example, are focused on the US row-crop market for the time being.
Weed detecting cameras and processors by Bilberry, featured on Agrifac AIC Plus
Perhaps the most ambitious spray technology was shown by Precision AI. Utilizing a large-fixed wing drone, the company aims to detect and spray weeds while operating at 60-to-70 km per hour. A hybrid power unit has an internal combustion motor that generates electrical power for rotors. This type of design offers significantly longer flight times than the 15 minutes currently possible with battery-driven units. Fascinating.
Precision AI concept spot spray drone, fixed wing with vertical take-off and landing
Spray drones also featured in the demonstration space at Ag in Motion despite the fact that this application method remains illegal for pesticides in Canada. It’s astounding what types of advancements each year brings. DJI is the global leader with three models available in Canada, including the 8-litre capacity T10, the 20-litre T20, 30-litre T30, and soon, the 40-litre T40. XAG, another leading manufacturer, showed a new two-rotor unit with rotary atomizers for excellent droplet size control. Flow management is nicely handled by accurate flow meters, but pressure sensors and displays are lacking in all units I’ve seen. Given that pressure is a big determinant of spray quality for hydraulic nozzles, that’s an oversight. We’ll continue to wait for this application method to be legal for pesticides in Canada.
XAG drone with two rotors and two rotary atomizers
As always, the show was full of old friends and catching up was welcome after the recent isolation. The opinions and advice from our peers play a big role in agriculture, where relationships and reputation still govern business alongside product features and cost. Trade shows are the perfect place for all of that to come together. Welcome back, old friend.
This work was performed with Mike Cowbrough, OMAFA Field Crop Weed Specialist.
In the early summer months, many field and specialty crop operations collect rainwater (or possibly pump water from holding ponds) into storage tanks for use as a carrier in spray applications. These tanks may be stationary, or they may be part of a nurse or tender truck that delivers both water and chemistry to the field as a means of improving operational efficiency.
In the case of translucent poly tanks, which are commonly used because of their light weight, custom shape, and low price point, light exposure will grow algae. Algal populations multiply exponentially and will clog spray filters and negatively affect filling. In response, growers use home-grown algicides such as copper sulfate, lengths of copper pipe, household bleach, chlorine, bromine, etc. They do so with little or no guidance and therefore little or no consistency. Beyond the obvious questions surrounding efficacy, it is unknown whether these adjuncts create physical or chemical incompatibilities in the tank mix. If so, there is the potential for reduced efficacy and/or crop damage.
We tested popular methods for algae control by inoculating a series of 10 L translucent plastic jugs with an algal population sourced from a southern Ontario holding pond. The population was left to acclimate and generally establish itself (aka colonize) before we introduced some form of control. Each jug was then gently stirred and emptied through a sieve for qualitative assessment.
In a parallel experiment, we introduced the same algicides to fill water and conducted spray trials. 10 L volumes were mixed with a field rate of glyphosate and sprayed on RR soybeans. Weed control was assessed and soybean yield measured for each treatment.
Algicide Efficacy Experiment
In each treatment, tap water was mixed with a micronutrient growth media (from the Canadian Phycological Culture Centre at the University of Waterloo). This was an unsterilized 10% WC(ed) solution intended to provide micronutrients for algal growth while minimizing fungal and bacterial growth.
The source algae were collected from the bottom of a holding pond from a farm in Guelph, Ontario. Algae were homogenized and equal parts added to each jug. The jugs were former 10 L pesticide containers thoroughly rinsed and sprayed with Five Star’s “Star San” non-rinse sterilizer. Tank solutions were gently bubbled (one bubble every 10-15 seconds) with air from an aquarium pump. Air was balanced using a manifold and introduced via diffusion stones at the bottom of each jug.
Algae sourced from a farm’s holding pond near Guelph, Ontario. Algae was homogenized before inoculating treatment jugs with equal parts.
Treatments
Each treatment was tap water plus growth media inoculated with algae and exposed to a natural diurnal/nocturnal cycle unless otherwise indicated.
Container was spray-painted black to exclude light
Ammonia
“Scotch Bright” copper-coated scour pad. (copper is often introduced as copper sulfate at 1 cup / 1,000 US gal. or a short length of copper pipe)
Bromine (sourced from a local pool supply store)
Treatment Number
Treatment Name
Rate (/US Gal.)
Rate (% v/v)
Rate (/10 L final volume)
1
Control (no algicide)
2
Shaded
3
*Household bleach
1/4 tsp
0.00033
3.3 mL
4
Black container
5
*Ammonia solution
1/4 tsp
0.00033
3.3 mL
6
Copper-coated scour pad
7
Bromine
1/32 ml
0.000004
0.04 g
Table 1. *Bleach and ammonia should never be added together as they produce toxic chloramine gas.
Method
On July 12, jugs were loaded with water and growth media and inoculated with algae. They were bubbled gently for one week to establish a stable algal colony. On July 19, algicides were added, or transferred to shade or black-out conditions. On August 31 (approximately six weeks later), jug contents were gently stirred and filtered through white cloth for qualitative assessment.
Building up algal population for each jug. Note air lines through lids for slow, intermittent bubbling. Algae was not moved to black container or to the shade until after the first week of acclimation.Almost six weeks after algicide was added, jug contents were gently stirred and poured through white cloth to collect algae and establish how easily the liquid passed through.
Observations
The results of all seven treatments, plus photos of the copper-coated scour pad.
(1) Control. Liquid poured slowly through cloth. Algae was still alive and healthy. It formed some clumps but was not as thick as other treatments.
(2) Shaded. Liquid poured fast and easily through cloth. Was particulate in texture rather than clumpy or gelatinous. Very little mass and entirely brown, suggesting it was dead.
(3) Household bleach. Liquid poured easily through cloth until the clump of algae sitting at the bottom of the jug came out (i.e., most algae were not suspended). Thick mat of healthy-looking algae (note profile photo #3 below). Much greener and thicker than the control (1).
(4) Black container. Liquid poured fast and easily through cloth. Algae retained a little green coloration (more than the shaded condition (2)) but was particulate and not as healthy as the control (1). We intended for this treatment to exclude all light, but it was still able to enter at the bottom where the jug wasn’t completely painted. This may have kept the algae alive.
In an oversight, the jug was not completely painted. This left a source of light at the bottom edge that may have helped sustain algae.
(5) Ammonia. Very difficult to pour liquid through the cloth (note profile photo #5 below). The only condition where a mat of algae was floating at the top of the jug rather than settled at the bottom. It was healthy, green and thick.
(6) Copper. The most gelatinous of all conditions, the liquid took the longest to pass through the cloth filter. While the algae seemed brown and dead, the gel would be very problematic during sprayer filling and spraying. Note that the copper scouring pad (shown unrinsed) has nothing growing on it.
(7) Bromine. Like the household bleach condition, liquid poured easily until the healthy mat of algae at the bottom of the jug came out (i.e., most algae were not suspended). Note profile photo #7 below.
Profile shots of treatment 3 (Bleach), 5 (Ammonia), and 7 (Bromine).
Spray Efficacy Experiment
Ideally, adjuncts added to carrier water are inert. That means they don’t reduce a herbicide’s effectiveness on susceptible weeds or increase crop injury. For example, hypochlorite (found in bleach and in chlorinated water) reduces the biological effectiveness of low concentrations of isoxaflutole (the active ingredient in herbicides such as Converge and Corvus). However, when added to higher, agriculturally-relevant concentrations, the reduction in efficacy wasn’t considered significant (Lin et al., 2003). Conversely, bromide has been added to certain herbicides to improve performance (Jeschke, 2009).
There’s precious little information about synergistic or antagonistic effects from adding bleach, ammonia, copper or bromine to herbicide carrier water. To learn more, we added each of these adjuncts to the standard rate of glyphosate (900 gae/ha – 0.67 L/ac). Using a CO2-pressurized plot sprayer, the solution was applied to <10 cm tall weeds at 150 L/ha (15 g/ac) in glyphosate tolerant soybean at the 2nd trifoliate stage of growth (Elora Research Station, Ontario).
Visual crop injury was evaluated at 7 and 14 days after application. Weed efficacy was evaluated at 14 and 28 days after application. Soybeans yields were collected using a Wintersteiger plot combine and adjusted to a moisture content of 14%.
Weed Control
All treatments provided excellent control (>90%) of the weeds emerged at the time of application. Table 2 (below) presents the % visual control 28 days after application.
Carrier Treatment (glyphosate 540 g/L at 900 gae/ha or 0.67 L/ac)
Lamb’s-quarter
Green pigweed
Witch grass
Green foxtail
1) Control
0
0
0
0
2) Shaded
100
100
100
100
3) Household bleach
100
100
100
100
3a) Household bleach – added prior to mixing
95
97
100
100
4) Black container
100
100
100
100
5) Ammonia
100
100
100
100
6) Copper-coated scour pad
100
100
100
100
7) Bromine
100
100
100
100
Table 2. Visual control of lamb’s-quarter, green pigweed, witch grass and green pigweed at 28 days after the application of glyphosate 540 g/L at 900 gae/ha mixed with various carrier treatments intended to prevent algae growth. Treatment numbers correspond with the soybean injury and yield image below.
Soybean Injury and Yield
There was no noticeable crop injury from any treatment (figure below) and yields were not significantly different from the control treatment (Table 3). However, when bleach was added prior to mixing, we did observe a trend in reduced soybean yield. We’re unable to explain this observation, but suggest it may be an unrelated issue (such as field variability). There were no obvious signs of crop injury, and the treatment provided excellent weed control.
Photographs of each plot 14 days after application. The number/letter in each inset image corresponds to treatments in Tables 2 and 3.
Carrier Treatment (glyphosate 540 g/L at 900 gae/ha or 0.67 L/ac)
Crop Injury (%)*
Avg. Yield (bu/ac)
Significance**
4) Black container
0
40.0
A
7) Bromine
0
39.6
A
2) Shaded
0
38.1
AB
3) Household bleach
0
37.6
AB
1) Control
0
37
ABC
5) Ammonia
0
36.9
ABC
6) Copper-coated scour pad
0
36.1
BC
3a) Household bleach – added prior to mixing
0
34.0
C
Table 3. Visual control of lamb’s-quarter, green pigweed, witch grass and green pigweed at 28 days after the application of glyphosate 540 g/L at 900 gae/ha mixed with various carrier treatments to prevent algae growth. *7 days after application. **Duncan’s multiple range test. Soybean yields that don’t share a letter in common are significantly different.
Discussion
We elected to use an extreme situation where a single application of algicide was applied to an established, healthy colony. It’s possible that regular applications of algicide in a volume of water with little or no algae could maintain that condition.
A treatment was considered effective if it slowed or halted algal growth, especially if it also degraded algal populations, causing them to become brown, thin, and/or particulate. Once in the spray tank, the shear forces created by circulation should disperse any dead or degraded algal masses, making it easier to pass them through filters and nozzles.
The shade treatment appeared to kill algae as well as cause degradation. Second place went to the black-out treatment, where some light was unfortunately allowed in. This would have continued to fuel photosynthesis in the unpainted portion at the bottom of the jug. Conversely, the black exterior likely raised temperatures above >20 °C, which depresses most algal growth and may have contributed to the degradation.
Copper appeared to kill the algae but also created a gel that would pose problems to filters. Unlikely to be bacterial, as copper is known to suppress bacterial growth, it could have been caused by diatoms; certain invasive species are known to form brown jelly-like material endearingly referred to as “brown snot” or “rock snot”. Alternately, and according to work by J. Rodrigues and R. Lagoa, alginate polysaccharide can form viscous aqueous dispersions (such as gels) in the presence of divalent cations (such as copper).
No treatment appeared to reduce herbicide efficacy or affect crop health. However, unexpectedly, the household bleach added prior to mixing may have reduced soybean yield. Given the limited number of replications and the single plot location, we suspect this was a field effect, unrelated to the treatment.
Take Home
Based on these results, a combination of shade and light-excluding materials (e.g. black paint) would be the ideal approach to algae control. It’s cheap, effective, and doesn’t require periodic management. Buying black tanks is a good choice, or you can paint them. What you should paint them with is a matter of debate and there’s a very good Twitter thread on the subject if you’re interested.
An Aside: Algae in Ponds and Dugouts
We didn’t test this, but the question has come up and the best we can do is share some long-standing farmer wisdom. Some have used Aquashade dye to absorb the photosynthetic wavelengths and reduce algae buildup. Reputedly it is moderately successful. Another option is adding aluminum sulfate to the pond, and with a lot of agitation it should clarify in about 48 hours. Still others have added a few square barley straw bales to the water and found it to work surprisingly well (possibly an allelopathic response). Tie a rope to them and float them in the pond.
Citations
Jeschke, Peter. 2009. The unique role of halogen substituents in the design of modern agrochemicals. Pest Manag Sci, 2010; 66: 10–27
Lin, C.H., Lerch, R.N., Garrett, H.E. and M.F. George. 2003. Degradation of Isoxaflutole (Balance) Herbicide by Hypochlorite in Tap Water. J. Agric. Food Chem. 2003, 51, 8011-8014
“Precision agriculture” is many things to many people. In the context of spraying, let’s define it as “detecting and responding to variability”. One example of precision ag is the use of crop-sensing optics to efficiently and accurately direct spray application. This is nothing new to field sprayer operators, but did you know that before Ken Giles published the first paper on pulse-width modulating nozzles in 1989, airblast sprayers already had crop-sensing technology?
In the 1970s, Bert Roper noted the wastefulness inherent to citrus spraying. Losses to the ground of 30-50% and off-target drift of 10-20% of applied volume were (and still are) not uncommon for airblast sprayers. So, using Polaroid’s autofocus technology, and enlisting the help of a few engineers, they developed an ultrasonic sensor system that enabled a computer to “see” the target tree and engage nozzles accordingly. He and son Charlie built prototypes in their kitchen before proving it in their family groves, spraying 10 gal/ac instead of the usual 250 gallons. The first Tree-See system was sold to Cola-Cola in 1984.
Figure 1 Tree-See on a Swanson sprayer (www.treesee.com)
This technology is still used today; Sensors detect specific zones on the canopy and actuate boom sections, or individual nozzles, to only spray the target zone. But optics and machine learning are evolving. Now they can modulate flow from individual nozzles in response to changes in canopy density. To be clear, that’s not just “on/off”, but variable flow.
Eventually, these systems will be able to identify and respond to specific pests (or pest damage) and adjust plant growth modifier rates based on canopy density or bloom counts. The possibilities are amazing. As an aside, interested readers can learn more about airblast sensors in this excellent article from Oregon State University which one of the authors later summarized for us here.
Figure 2 LiDAR and control interface for a Smart Apply system fitted to a Turbomist sprayer
However, as operators embrace this technology, they should be aware of the current limitations. Canopy-sensing optics are great at managing waste (their primary selling point seems to be pesticide savings), but this depends on crop morphology and planting architecture. It makes sense to not spray what isn’t there, but the gaps may not be as big as you think.
Non-continuous canopies require the spray to lead and lag to some extent before and after passing the target to ensure sufficient coverage. Given the difficulty inherent to spraying to the tops of tall canopies, some specialists believe the top nozzles should never disengage. And, in the case of uniform canopies that form continuous hedge-like rows, the potential savings is greatly reduced.
Further, all of these systems assume that application efficiency is primarily dependent on matching liquid flow rates to the profile (or perhaps density) of the target canopy. I don’t believe that’s true. At least, not entirely true. The impact of air settings on coverage efficiency and efficacy seems to have been marginalized.
For example, these sprayers do not account for the spray’s ability to span the distance from nozzle to target (i.e., transfer efficiency). That depends on the droplet size, sprayer air settings and the environmental conditions – none of which are monitored by sprayer optics. They also cannot “know” if the spray gets intercepted by the target (i.e., catch efficiency) or if it deposits a biologically-active residue on the target surface (i.e., retention). Droplets must be retained by the target surface and not bounce or run off.
What this means is that these sprayers, like any sprayer, can only promise “coverage potential”. Operators are still required to perform the following tasks:
Optimize air direction and air energy in relation to canopy size, travel speed and environmental conditions.
Use water-sensitive paper, or some other means of quantifying coverage, to ensure your target receives threshold coverage.
Monitor and adjust practices throughout the season in response to changing conditions.
HOL’s Intelligent Spray Application (I.S.A.) system employing Weed-It sensors.
So what’s missing? How do we progress beyond what is arguably a sophisticated rate-controller?
In my opinion, I believe the pitcher needs a catcher – a closed-loop feedback system. Optics would identify the target, nozzle flow would respond, and then a digital spray sensor in the target canopy would detect and report coverage back to the sprayer so machine learning could make iterative adjustments in real-time.
Spray-sensors are not a new idea, as wetness-detection systems have been used in forestry since the 70s. But, a sensor that can discern spray coverage would yield far more detail, and once again it seems Ken Giles is a pioneer in this concept. Such a sensor, integrated with sprayer optics and machine learning, could summarily account for all the unknowns that interfere with spray from the moment it’s released to the point that it (hopefully) lands. That’s some serious crop-adapted spraying.
And yes, it would be fantastic if there were some manner of anemometer tied to a baffle or louvers in the spray head. Air energy could be balanced between up- and down-wind sides, and further adjusted to compensate for the distance to the canopy… but I’m dreaming in technicolour, now.
Until then, sprayer eyes can only blindly dictate the release of spray into the airstream based on an assumed coverage constant (e.g., 1.2 oz./ft3). It remains for the sprayer operator to act as the brain, optimizing sprayer settings, quantifying coverage, and making changes to reflect conditions.
Learn more about how to optimize the fit between your airblast sprayer and your target by downloading a free copy of our Airblast 101 textbook.
