Summary The Economics of Spot Sprays – Sprayers 101 sprayers101.com
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"Sprayers 101" covers the economics of spot sprays, discussing their benefits in terms of cost-saving by targeting weeds, but also mentioning that some companies charge fees for this service.
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Key Points
- Spot sprays can save product by only spraying the weeds instead of the whole field.
- User fees for spot sprays can complicate the cost equation.
- The cost of spot sprays is influenced by the herbicide price, algorithm fees, and potential misses.
- Spot sprays with no background run the risk of misses and potential yield loss.
- Spot sprays can reduce crop exposure to herbicides with low crop safety.
Summaries
36 word summary
"The Economics of Spot Sprays" is covered in "Sprayers 101," which discusses spray application, calibration, maintenance, nozzle selection, and specialty sprayers. Spot sprays save costs by targeting weeds, but some companies charge fees for spot spray
83 word summary
The Economics of Spot Sprays is a topic discussed in the document "Sprayers 101." The article covers various aspects of spray application, including general concepts, calibration, cleaning and maintenance, and nozzle selection. It also provides information on specialty sprayers
Spot sprays offer the potential for cost savings by only spraying weeds instead of the entire field. However, some companies charge user fees for the use of their spot spray detection algorithms, which can affect the cost equation. The fees range from $3 to
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The Economics of Spot Sprays Sprayers
101
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The Economics of Spot Sprays
Posted on
September 11, 2023
(September 14, 2023)
by
Tom Wolf (Nozzle_Guy)
About Tom Wolf (Nozzle_Guy)
Tom Wolf is based in Saskatoon, SK and has 33 years research experience in the spraying business. He obtained his BSA (1987) and M.Sc. (1991) in Plant Science at the University of Manitoba, and his Ph.D. (1996) in Agronomy from the Ohio State University. Tom focuses on practical advice that is research-based to improve the efficiency of producers.
See all posts by
Tom Wolf (Nozzle_Guy)
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 Rometrons WeedIT and Trimbles WeedSeeker, no fees are charged.
Fees essentially identify a pesticide price point below which spot sprays are not economical. Lets 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 lets 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 thats not the whole story. Spot sprays arent perfect. Companies are quoting a minimum weed size of about diameter (say, 6 mm), below which the plant cant 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 werent 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 its offset by the yield benefit of removing the weeds. Spot spraying can also open up new uses for herbicides with low crop safety.
Lets assume the yield benefit of avoiding phytotoxicity to the crop is $10 per acre. Well 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, its 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.
Ive 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.
Im 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.
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