Category: Boom Sprayers

Main category for sprayers with horizontal booms

Basic Sprayer Math Demystified
Sprayer math can be intimidating, but the effort gives solid value. When combined with a calibrated sprayer you reap the following benefits:
- Estimate how long a job will take.
- Estimate how much spray mix is required.
- Estimate how much crop protection product must be ordered for the season.
- Populate spray records which allow you to review practices, respond to enquiries and satisfy traceability requirements.
There are many ways to perform sprayer math, and you need only look to local pesticide safety courses, industrial catalogues, and extension resource centres for examples. If you’re already comfortable with your current method, don’t mix and match with others. Sprayer math is a series of related calculations that employ constants to keep the units straight. It’s all or none.
Walkthrough
Let’s start with the classic, US Imperial formula for calculating the required nozzle output. In other words, you want to know which nozzle size you need to get the volume-per-planted area you’re aiming for. This is the bread-and-butter formula that seems to be needed most often, so that’s why we list it first.
In order to determine nozzle size (gallons per minute), you’ll need to know your target volume (gallons per acre), your average travel speed (miles per hour) and your nozzle spacing (in inches). The number “5,940” is a constant that handles all the unit conversions. It is what it is.
GPM = [GPA x MPH x W] ÷ 5,940
Of course, this formula can be adjusted to allow you to solve for any factor, as long as you’re only missing one piece of information. Algebra is all about solving for X, or in other words, determining some unknown variable. I know, it’s been a long time since you learned this in school and it doesn’t come easily to most. I propose brushing up on the basics using a series of three great YouTube videos from “Mathantics“
As we noted earlier, you can do a lot more with sprayer math than just pick the ideal nozzle. But before we continue, a warning: If you live where units are strictly US Imperial, or strictly Metric, then Canada’s odd hybrid “Mock-tric” units can get a little confusing. The rest of this article attempts to be globally-relevant by including examples of both Metric and US Imperial formulae, but watch out for unit conversions. If at any time you don’t see the units you’re looking for, you can consult our exhaustive list of unit conversion tables.
Grab your calculator or favourite smart phone app – it’s math time!
Don’t be intimidated. With a little practice, sprayer math gets easier and it’s always worthwhile. The real trick is navigating unit conversions.
Step 1 – How large is the area you need to spray?
Multiply the length of the area you plan to spray times the width. If you are using metres, then divide the product by 10,000, which is the number of m² in a hectare (ha). For feet and acres, divide by 43,560 which is the number of ft² in an acre (ac):
Step 2 – How much product is needed to spray the area?
Consult the rate(s) shown on the label. In Canada, rates are often based on planted area (E.g. hectares). In Australia and New Zealand, they may be based on row length (not covered in this article). If you measure your area in acres, you’ll have to convert the rate by multiplying by a constant: 0.4.
Now multiply the area you want to spray (step 1) by the rate (step 2).
Step 3 – How far can you go on a full tank?
You know your sprayer output (determined through calibration) so you divide that into your tank size. Watch your units:
Step 4 – How much pesticide per tank?
Multiply the area that can be sprayed per tank (Step 3) by the pesticide rate (Step 2). Again, watch your units:
Step 5 – How much area is left to spray?
Just subtract what you’ve already sprayed from the total area.
Step 6 – How much pesticide in the last, partially-full tank?
Multiply the area you have left to spray (Step 5) by the pesticide rate (Step 2). Yes, watch your units:
Step 7 – How much spray mix will I need for the partial tank to finish spraying the total area?
Multiply the area you have left to spray (Step 5) by the sprayer output (determined through calibration). Guess what? Watch your units:
Sample problems
Time to test your knowledge. Let’s suppose you want to apply a product rate of 3 L/ha to your blueberries. You calibrate your sprayer and determine your output to be 50 L/ha. Your tank holds 400 L of spray mix. Your planting is 500 m long and 200 m wide.
Q1 – How large is the area you need to spray?
Q2 – How much product is needed to spray the area?
Q3- How much area can be sprayed on one tank?
Q4 – How much product should be added to a full tank?
Q5 – After the tank is empty, how much area is left to spray?
Q6 – How much product to add to the last, partially full tank?
Q7 – How much spray mix will be needed to finish spraying?
Exceptions
Certain situations aren’t covered in this article. If you are spraying a greenhouse, the math is different. If you are performing a banded application, the math is different. And, if you’re an airblast operator trying to reconcile why a pesticide label uses planted area rather than canopy volume for its rates, you’re in for a lot of additional reading. Some of that latter process can be summed up in this infographic:
When you find a method that works for you, write it down and keep it with your spray records. Happy spraying!
May 7, 2024

Nitrogen Application Technology in Winter Wheat

With an ever growing selection of options for nozzles and streamer bars, many growers are asking the question, what should I outfit my sprayer with for winter wheat liquid fertilizer applications? Well, it depends on what are you trying to accomplish.

If the goal is to push your winter wheat management and improve yields, then the accurate and uniform application of liquid nitrogen is key. Selecting the appropriate sprayer technology can have a huge impact. Using a twitter poll, we learned that growers use many methods:

3, 5, 6 or 7 hole streamer nozzles
Flood nozzles
3 or 5 hole streamer bars

Let’s look at some of the options and consider why you might choose one technology over another.

Floods on a Terra-Gator. Photo courtesy of Kyle DeCorte.

Air Induction, Conventional Flat Fan or Flood Nozzles

Let’s get this one out of the way first. Air induction (AI), conventional flat fan and flood nozzles are a no-go when it comes to applying 28% UAN in winter wheat. Dr. Peter Sikkema (University of Guelph) demonstrated that when 28% UAN was applied with an AI nozzle there was an increase in visual crop injury (Table 1).

He also showed that injury increased substantially when tank-mixed with herbicides and when nitrogen applications were delayed (Table 2). So, while AI nozzles are great for herbicide applications, they are not suitable for 28%. Growers should consider fall weed control to avoid the need for spring herbicide applications.

Table 1. Potential yield loss associated with applying UAN 28% as overall broadcast treatment using FloodJet or TeeJet nozzles. ¹1 gallon (Imperial) = 1.2 U.S gal. Source: P. Sikkema, University of Guelph (RCAT), 2008–2013 (OMAFRA Pub 811: Agronomy Guide).

Application Combination	Visual Injury	Yield
200 L/ha water (18 ¹g/ac water)	0%	6.4 t/ha (95 bu/ac)
150 L/ha water + 50L/ha UAN (13.4 g/ac water +4.5 gal/acre UAN)	3%	6.4 t/ha (95 bu/ac)
100 L/ha water + 100L/ha UAN (9 g/ac water +9 g/ac UAN)	5%	6.1 t/ha (91 bu/ac)
50 L/ha water + 150L/ha UAN (4.5 g/ac water +13.4 g/ac UAN)	7%	6.1 t/ha (91 bu/ac)
200 L/ha UAN (18 g/ac UAN)	9%	6.0 t/ha (89 bu/ac)

Table 2. Crop injury (%) and yield (bu/ac) of winter wheat following an application of 28% UAN (400 L/ha) alone with air induction nozzles and with various herbicides compared to an untreated control that received the same amount of nitrogen. Source: Dr. P.H. Sikkema, 3 trials from 2008-2010, University of Guelph (Ridgetown Campus) – Additional information on tank-mixing with herbicides can be found here.

Treatment	Herbicide rate/ac	Injury (%)	Yield (bu/ac)
control (unsprayed)	——	0	105
28% UAN alone	——	6	105
28% UAN + Infinity	0.33 L	9	104
28% UAN + Buctril M	0.4 L	8	103
28% UAN + Estaprop XT	0.48 L	9	102
28% UAN + Refine M	12 g + 0.36 L	17	99

Streamer Nozzles

Streamers significantly reduce crop injury when applying UAN 28% in winter wheat. Growers in Ontario are using a range of 3, 5, 6 and 7 hole nozzles. These nozzles provide even coverage and minimize burn compared to flat-fan or flood nozzles; however, boom height can have an impact on crop injury. This is particularly important with 3 and 6 hole streamer nozzles. If there are significant variations in boom height (e.g. uneven emergence, uneven land, or a boom with excessive sway and yaw), significant crop injury can occur. This is exacerbated by hot and dry conditions.

The damage is the result of non-uniform coverage. Streamers deliver spray in a triangular shape. If the boom is too low gaps in the spray pattern reduce coverage. If the boom is too high the crop may receive increased overlap, resulting in crop injury. Therefore, these nozzles are an excellent option for apply UAN 28% to winter wheat crop (see image below) as long as boom height can be managed effectively.

Pro tip: 28-0-0 often has crystals so strainers are important.

UAN 28% being applied uniformly to winter wheat using 3 hole streamer nozzles. Photo courtesy of: Jim Patton.

Streamer Bars

Streamer bars (see image below) may be the best choice. Streamer bars deliver liquid nitrogen to the crop vertically. This allows for even distribution across the winter wheat crop at various boom heights, often permitting great speed. Some even have a sliding orifice to permit an easy transition between rates. Research performed in Kentucky showed that streamer bars produced a 2.8 bu/ac yield advantage compared to 3 hole streamer nozzles, and a 4.9 bu/ac yield advantage over 7 hole streamer nozzles.

Some may argue those aren’t significant yield advantages, but most Ontario growers would argue differently. Streamer bars provide uniform coverage no matter the state of emergence, boom height, topography or even wind conditions. Streamer bars can be adapted to most sprayers and are available in 15″ or 20″ spacing. The only caveat is that they can be fragile and can make folding the boom difficult.

Chafer streamer bar. Photo courtesy of Alex Zelem.

Other Ways to Reduce Burn

In addition to proper nozzle selection there are a few things you can do to reduce the risk of crop injury from N applications.

Avoid applications of 28% when the crop is stressed or during hot and dry conditions.
If conditions are more conducive for crop injury, increasing water volumes or applying less N can also help reduce burn significantly.

At the end of the day it is important to remember the end goal – maximize yield potential. If we can deliver UAN 28% as uniformly as possible to a standing winter wheat crop while minimizing crop injury, the 100+ bu/ac wheat crop will be well worth the effort.

Here’s Peter Johnson (@WheatPete) to tell you more in this RealAgriculture Wheat School episode:

May 3, 2024

How to Succeed with a Soil Drench Application in Strawberries
In 2016, Ontario berry growers were surveyed to determine the typical spray volume they used to apply unspecified crop protection products. For strawberry growers (day-neutral and June-bearing), the results spanned 50 to 1,000 L/ha (~5 gpa to ~100 gpa). In an earlier survey (2013), respondents specified 250 to 650 L/ha (~26.5 to 70 gpa) for fungicides, herbicides and insecticides. Miticide applications were as high as 750 L/ha (80 gpa).
This rather wide span of carrier volumes shouldn’t be surprising. No matter the horticultural cropping system, the choice of carrier volume reflects the operation’s unique pressures and priorities. These variables include, but aren’t limited to, operation size, spray equipment, crop varieties/staging, geography, and pest profiles. The ultimate goal is to achieve threshold coverage (i.e. efficacy) while maximizing productivity.
However, even the highest carrier volume reported did not reach the volumes required for those crop protection products intended to drench the soil. These products can span a range of 1,200 to 2,000 L/ha (~128 to 214 gpa). Experienced matted-row strawberry growers employ different methods to apply soil drenches, and we will discuss them later in the article. But first let’s address three common factors that must be considered:
Know the target
If (for example) the target is white grubs in the root zone, or phytopthora root rot, then the spray should be focused at the base of the plant in a banded application. Performing a broadcast application that covers the alleys as well as the plant rows may represent wasted spray. Knowing the target can help make the most efficient use of carrier.
Know the soil
Soil that is compressed or has high clay content won’t soak up water as quickly as drier, looser or sandier soil. If the beds are raised and resist absorption, much of the volume will run off into the alleys. This may not be desirable if the target is the raised bed itself. The following basic water movement principles come from the Manitoba Agriculture, Food and Rural Initiatives Soil Management Guide.
- Water flows more quickly through large pores (sandy soils) than small pores (clay soils); water is held more tightly in small pores (clay soils) than in large pores (sandy soils).
- Water moves from wet areas to dry areas (not necessarily by gravity) due to forces of adhesion and cohesion. This is called matric flow.
- Water will not move from small soil pores to large soil pores unless conditions are saturated.
Know the weather forecast
Spraying on a hot, dry day means a higher rate of evaporation. As the carrier evaporates, the product will have less opportunity to infiltrate the soil. Conversely, applying product just before a heavy rain can result in a much diluted product being rinsed too deeply into the soil and beyond the target area.
Consider that one millimetre of rain on one hectare of land is 10,000 litres. That seems like a lot, but how deeply does it infiltrate into soil? One way to know is to use calculations based on soil porosity and bulk density. From these calculations it can be generalized that 25 mm of rain will infiltrate 45 mm into dry, sandy soil, but only 32 mm into dry clay soil. Remember, that 25 mm of rain represents 250,000 L/ha!
Perhaps the best way to know how far water will infiltrate the soil is to use a soil probe (aka soil sample tube). They can be purchased from local dealers for about $100.00 CAD, or they could be borrowed from whomever provides soil sampling services in the area. For the best results, perform this test in multiple locations in the field.
The soil probe. See how far water infiltrates soil by taking core samples.
So what methods do strawberry growers employ to apply a drench? Here are the top three:
1. Slow down
Some growers elect to use their existing sprayer setup, but they slow down to get more volume on per hectare. For example, if the grower normally applies 500 L/ha (53.4 gpa) driving at 5 km/h (3.1 mph) they would have to drive 1.25 km/h (0.78 mph) to achieve the 2,000 L/ha some labels require. If the sprayer tank held 1,500 litres (~400 US gallons) that would mean doing 0.75 hectares (1.9 acres) to a tank compared to the normal 3 hectares (7.5 acres). That would be four times as long, without considering the time for the extra refills.
Alternately, but related to slowing down, is double-pass spraying. In this case the tank is mixed at half-rate and the operator makes a pass through the field. Then, a second half-rate tank is applied immediately afterwards, ideally driving from the opposite direction. This effectively gives a full rate of product in a higher volume of water.
2. Re-nozzle
When slowing down is not enough (or not an option), some growers elect to re-nozzle. It may be tempting to increase the operating pressure to increase output on existing nozzles, but that makes finer droplets which tend to drift off target. The largest hollow-cone nozzles will only emit ~870 L/ha at 5.0 km/h (93 gpa at 3.1 mph) and that’s at 125 psi, which many trailed sprayers cannot manage. Further, many labels indicate a need for Coarse droplets in a drench, and hollow cones cannot produce such large droplets.
There are a limited number of flat fan nozzles that can achieve sufficiently high rates, and even then they must be used at slightly slower travel speeds. For example, the TeeJet AI11008 used at 70 psi will apply 145 gpa (~ 1,350 L/ha) with a Very Coarse spray quality at 4 mph (6.4 km/h). Driving slower can rise those volumes considerably. Alternately, streamer nozzles (e.g. TeeJet’s 5 or 7 hole StreamJets) require lower pressures (up to 60 psi) to emit as much as 2,310 L/ha at 5.0 km/h (247 gpa at 3.1 mph). The grower can maintain their travel speed, but will still have to refill more often.
3. “Wash In” the spray
Still another choice is to apply the product using the existing sprayer set-up, using a typical carrier volume, just prior to a rain event or sprinkler (not drip line) irrigation. For example, if the grower normally applies 500 L/ha (53.5 gpa), they would continue to do so. If the grower is relying on rain to wash the product in, it should be sufficient precipitation to move the product to the desired soil depth. Where sprinklers are an option, this can be controlled, and the depth of infiltration tested with a soil probe. Washing in the spray should take place as soon after application as possible to ensure the product is distributed evenly into the soil.
Thanks to Pam Fisher, former OMAFRA Berry Crop Specialist, and Anne Verhallen, former OMAFRA Soil Management Specialist, for their contributions to this article.
February 26, 2024
The Economics of Spot Sprays
At first glance, spot sprays are a no-brainer. Why spray a whole field when you can save product by spraying just the weeds?
But then the first commercial green-on-green systems introduced user fees, complicating the cost equation. Companies sell the hardware, and charge a fee for use of their detection algorithms.
Currently, costs range from $3 to $4 per acre, and this fee is either applied once per season (no matter how many times the algorithm is used on a specific field) or each time the system is deployed. As of September, 2023, Bilberry (via Agrifac as AICPlus, but also via Goldacres in Australia and Dammann in the EU) was using the former approach, and John Deere with See & Spray Ultimate in the US was using the latter. Greeneye is not charging fees. For Green-on-Brown systems, the likes of Rometron’s WeedIT and Trimble’s WeedSeeker, no fees are charged. In the summer of 2024, John Deere announced they would only be charging fees on acres that were not sprayed, i.e., areas in a field in which the weed sensing technology identified no reason to turn on a nozzle. The fee question is likely not quite settled yet.
Fees essentially identify a pesticide price point below which spot sprays are not economical. Let’s take an example of a $4.00 per acre price of herbicide, broadcast (column 1 in Table 1). The “Gross Cost” of the broadcast treatment is simply the cost of the herbicide. For a spot spray, if a specific field requires just 25% of the herbicide (a 75% saving), the herbicide cost is $1/acre (column 2). Add a $4.00 per acre algorithm fee, the Gross Cost is $5.00 per acre. Broadcast spraying would cost $4.00 per acre, less than the spot spray cost. The cost for herbicide at which spot sprays become economically interesting is therefore above $5.00 per acre.
The gross cost of a spot spray pass can be calculated as follows:
Gross cost = (pesticide price * use rate) + use fee
Where “use rate” is the proportion of the field sprayed with the product.
Table 1: Spray cost scenarios for low value crops and herbicides
Now let’s assume a weedy field, one in which only a 50% saving is possible (column 3). Herbicide cost is now $2/acre, added to the $4.00 algorithm fee, for a total cost of $6.00 per acre (column 3). The weedier the field, the higher the herbicide price needs to be for a spot spray to be justifiable. Spot sprays without fees, on the other hand, allow the user to keep all the savings (columns 4 & 5), and will be the most economical option no matter the herbicide cost.
But that’s not the whole story. Spot sprays aren’t perfect. Companies are quoting a minimum weed size of about ¼” diameter (say, 6 mm), below which the plant can’t be detected. Some weeds are invisible due to shading by crop residue or other plants.
The technological answer to this problem is to implement a low-rate broadcast spray in the background. The lower rate is sufficient to kill the smallest weeds, but it reduces the overall savings. Current systems are capable of doing this due to their use of PWM valves that can deliver broadcast and spot sprays at the same time from the same nozzles.
Use of a background spray adds to the herbicide costs. If a 30% broadcast background spray were used in this example, it would add $4.00 * 0.3 = $1.20 to the cost (not shown in table). The assumption is that the lower rate broadcast would easily kill the smallest weeds that were undetected, without adding to the likelihood of resistance development from under-dosing. The assumption is also that large weeds weren’t undetected.
Users who opt for a spot spray with no background run the risk of having misses that would not be incurred with a broadcast spray. The cost of these misses depends on the situation. In some cases, it is inconsequential. A tiny weed may not cause much harm if the crop is larger and growing vigorously.
But what if the weed is competitive, and could ultimately cause yield loss? A re-spray may be required. What if this weed later causes harvesting difficulties that may necessitate a desiccation spray? What if it is resistant, and its seed production causes problems in the future? Those costs need to be considered.
In this case, we are assuming the cost of a miss at a conservative $5.00 per acre, which could be the cost of operating the sprayer for a re-spray. The cost would apply to all spot sprays equally, but not to the broadcast spray. Now the broadcast spray, still at $4.00 per acre, is the most economical.
There are also potential benefits to consider. One is the yield loss caused by the application of a herbicide with low crop safety. Think of Status (dicamba and diflufenzopyr) in corn, or metribuzin in lentils. Limiting the exposure of the crop to the herbicide reduces the potential yield loss. We rarely consider this effect because it is quite uncommon, but when it does occur it’s offset by the yield benefit of removing the weeds. Spot spraying can also open up new uses for herbicides with low crop safety.
Let’s assume the yield benefit of avoiding phytotoxicity to the crop is $10 per acre. We’ll apply this saving to the proportion of the field that is not sprayed. The spot sprays regain their advantage, but only in cases where the weed density was low or no fees were charged (“Crop Health Benefit”, Table 1). Where weeds were sprayed in larger proportions of the field area, yield benefits were reduced.
We repeat the whole exercise for a higher value crop, with more expensive treatments but also higher penalties for misses and greater crop phytotoxicity costs.
First considering only the “Gross Cost” scenario, the advantage of the spot sprays grows in this scenario (Table 2). But when the cost of a miss is added, it’s surprisingly close. As in the lower cost example in Table 1, the broadcast spray remains relatively competitive even with higher costs.
Table 2: Spray costs for higher value herbicides and crops
When we add a potential crop health benefit of $20/acre, the spot sprays regain their larger advantage.
Using the herbicide price as the variable and plotting the broadcast and spot spray costs, the place where these lines cross is the herbicide cost below which the broadcast application is most economical. In the example below, the use fee was $4.00, and the miss cost was $5.00. As expected, the “no fee” situation was always more economical than broadcast when no miss costs were added. As algorithm and miss costs were added, herbicide prices needed to be above $5.00 and $14.00, respectively for the spot sprays to be more economical than the broadcast application.
Figure 1: Spot spray costs as a function of herbicide prices, assuming a 20% spot spray use rate, with $4.00 algorithm fee or $5.00 miss cost added.
This exercise is not intended to declare winners and losers. Its purpose if simply to initiate a discussion about the overall cost of various approaches. What if owners of spot sprayers make, on average, more passes over the field? What would the value of a lighter, cheaper sprayer be on their bottom line? With less expensive sprayers, the fixed cost of a spray, or a re-spray would drop. Is there a benefit from reduced soil compaction? What if the use of more complex tank mixes, necessitated by resistance, jeopardizes crop safety? The benefit of spot sprays would increase.
Continued development of nozzles specifically for spot spraying, as well as better boom levelling, will improve spot spray economics because the smaller width and length of an applied band that stable booms allow will increase savings. As these take hold, they will tilt the calculations in favour of the spot sprays.
I’ve often repeated that the savings created by spot sprays ought to be re-invested in herbicide tank mixes, with a goal to prolong the utility of herbicides before resistance develops. This could ultimately create the biggest long-term return on investment because once herbicides are no longer effective, alternative strategies will be needed.
I’m as hopeful as anyone else that agriculture can retain the benefits of effective and safe herbicides for a long time to come. But it will only take one weed on a farm to become resistant to all available herbicides for major change to be necessary. The more time we have to develop these alternatives, the better. Spot sprays are definitely a part of that strategy.
September 11, 2023
Greeneye makes impressive debut
Green-on-green sprayer competes with Blue River and Bilberry
One distinguishing feature of the new agriculture is the rapid development of new technologies. Ideas move from concept to implementation at record pace, helped by an influx of talent and capital into this profitable sector.
Greeneye Technology is an example of this pace. Founded by entrepreneurs who met in the Israeli armed forces, they developed a software platform that identified crops, weeds, and other objects in agricultural fields from drone imagery. They recognized the opportunity to transition their software to a sprayer platform, and in 2017 decided to join the race, most notably competing with Blue River, Bilberry, Carbon Bee, and Xarvio, to create a green-on green spot sprayer.
Greeneye, in an amazing display of efficiency and speed, has been a commercial product for approximately one year in the US and has sold several units in Nebraska, Minnesota and Oklahoma, and next year will expand to North and South Dakota, Iowa, Illinois, Kansas and Texas. Having consulted for the company in its early years, I paid a visit to Peterson Farms Seed near Fargo, ND in early July 2023 to see the sprayer first hand at a field demo. By the way, kudos to PFS for bringing this technology to their customers to see. Have to love a business so committed to the cutting edge.
Figure 1: The Greeneye system was mounted on a Hagie STS 12 sprayer.
The Greeneye system was mounted on a Hagie STS 12 sprayer (1200 US gallon tank) with a custom 120’ boom manufactured for Greeneye by Millenium. Recognizing the agronomic need to broadcast pre-emergence herbicides along with a post-emergent spray, they company retained the existing plumbing system (tank, pump, wet boom) for this purpose. They added a smaller spot spray tank (240 gallons) with its own pump and wet boom for spot spraying.
Figure 2: A smaller spot spray tank was added to the Hagie. If necessary, spray mix can be pumped from the larger tank to this smaller tank.
This approach permits the flexibility of broadcasting a pre-emergent herbicide during burnoff alongside a post spot spray on emerged weeds. The agronomist in me likes this a lot. Broadcast pre-emergent herbicides are an important part of resistance management, particularly in the US.
Figure 3: The second (spot spray) boom is mounted behind the factory wet boom.
The new wet boom has a nozzle spacing of 10”, is fitted with three-nozzle-turret TeeJet bodies. The 10″ spacing allows for higher resolution of the spot spray, increasing potential savings compared to a 20″ spacing.
Figure 4: The spot spray nozzles are mounted at 10″ (25 cm) spacing.
The spray was metered through custom-made TeeJet DG4003 tips using Gevasol solenoids running at a speed-dependent frequency, maximally 100 Hz, with turn compensation.
Figure 5: Solenoids activate the spray when a weed is detected in that nozzle’s lane.
DG Nozzles use a pre-orifice to meter the flow at the rated amount, with an exit orifice slightly larger. This creates a pressure drop, resulting in a lower drift spray.
Figure 6: These Drift Guard nozzles are custom-made for Greeneye by TeeJet.
Figure 7: The blue DG pre-orifice meters the flow at 0.3 US gpm at 40 psi.
Looking at the spray quality and coverage on water-sensitive paper I thought the deposit looked just right. Spot sprays shouldn’t be too fine for risk of displacement from their intended band. We’re not seeing bundled nozzles with other spot spray systems, who leave nozzle selection to the operator. That can pose difficulties and possibly forfeit either weed control or savings.
Figure 8: The spray deposit shows adequate coverage and a good droplet size distribution for good placement accuracy.
Sectional control retains the plumbed resolution at this time, although nozzle-by nozzle resolution is in the pipeline. Cameras are mounted at 1.5 m intervals and can run up to 50 fps. Camera resolution is proprietary, but the company claims that weeds as small as ¼” diameter can be detected. In its current configuration, weed diameters of 1” are detected, leaving smaller weeds for the pre-emergent products. LED lights flash to illuminate the camera field of view, improving image consistency and permitting the system to run at night. The Greeneye system analyzes a captured image just once to make a spray decision, and does not use segmentation in its algorithm.
Figure 9: The camera and lights look ahead to provide the necessary time for the on-board computer to make the required calculations that determines the plant’s identity. Note the aspirated lens cleaner.
Like its competitors, the user can select from individual nozzle activation or, in “windy mode”, the addition of the adjacent two nozzles to create a three nozzle broadcast. The length of the band is automatically selected by the software, with no user input available. Sensitivity adjustments are currently by request to the factory, but will be available for operator control in 2024.
Greeneye provides its own cab monitor that works with the sprayer monitor on sectional control. The Greeneye monitor keeps track of the spray volume usage and provides an ongoing report to the operator.
The software is able to report back whether a detection was a grassy or broadleaf weed, a powerful piece of information for keeping track of weed patches and monitoring for emerging problems. Weed maps are already being produced as a proprietary tool, and will be generally available in 2024.
New Greeneye customers have their sprayer picked up at the yard and transported to Greeneye facility where the new boom, tank, and digital components are installed. The customer receives the converted sprayer, calibrated and ready to go.
In my judgement, the install was clean and tidy. Camera mounts are welded on, and an air jet can be used to keep the lenses dust free. Brackets for the GPU and other control boxes are unobtrusive, although the wiring does get a bit crowded in places. Everything is accessible.
Cost is $239,000 US at time of printing (July 2023). This gets the customer a Greeneye system for a 120 foot boom, a brand new aluminum boom, retrofit of the sprayer to dual tank, installation and warranty. Return on Investment (ROI) for a spot sprayer will depend on farm size and herbicide use. Based on observed savings to date, Greeneye estimates that for a farm larger than 3,000 acres the ROI would typically be less than 2 years.
Greeneye does not charge subscription fees for its algorithms. This last aspect is interesting as John Deere and Bilberry both charge for use of their algorithms on a per acre basis. John Deere, for example, charges $3/acre US for corn, and $4/acre for soybeans and cotton, each time you make a spot spray pass with See & Spray Ultimate.
Available Greeneye algorithms are for Green-on-Brown, and Green-on-Green in corn and soybeans as of July 2023. Cotton and milo will be available in 2024, and Greeneye is working on canola and wheat as well. Like Bilberry, they capture images from the cameras for use in algorithm learning, and accuracy and hit rate should be improving with time. Travel speeds of 15 mph are working well according to Greeneye.
As for performance, the proof will be in the pudding. The company in its wisdom did commission an independent evaluation at the University of Nebraska, Lincoln, and has made a summary of the university report available on its website. According to UNL, broadleaf weed control in corn with the spot sprayer was equivalent to the broadcast treatment, and grassy weed control was slightly less effective. UNL researchers noted herbicide crop injury (“Status”, dicamba + diflufenzopyr) was reduced with the spot spray. Of course, savings will be a function of weed density and the detection threshold chosen by the operator, but the addition of reduced crop injury resulting in greater yields could also be very valuable.
A recent investor and business partner is Farmers Business Network (FBN). FBN sees the opportunity for a spot sprayer to act as a scouting platform that helps evaluate the success of new pest management strategies.
Support on the ground is in the form of US staff with backgrounds in the spraying industry. Software development and digital troubleshooting remains in Israel.
Although I no longer have business links to Greeneye, I was happy to see this sprayer operating as well as it did. I remain convinced that spot sprays will be an essential part of our spraying future, for sustainability and resistance reasons. It is heartening to see these early successes and it will be interesting to see them continue to evolve.
July 28, 2023