⋅ BY JOHN LOVETT ⋅
Like any new technology, there is a learning curve to using it correctly, and the See & Spray from John Deere is no exception. A three-year field trial in Arkansas soybeans showed proper use of the technology can cut post-emergence herbicide use by half and save millions of dollars in expenses.
Researchers with the Arkansas Agricultural Experiment Station started the trial in 2022 using a See & Spray prototype to help determine the precision agriculture system’s capabilities in targeted herbicide applications. The system uses machine learning combined with real-time imagery from cameras to selectively spray herbicide on weeds in row crops.
According to Farm Progress, there are more than a dozen companies with interests in targeted spraying technology, including this system from John Deere.
Jason Norsworthy, Distinguished Professor of weed science for the experiment station, has evaluated the system in test plots at the Northeast Research and Extension Center in Keiser since 2017 as part of his broader research on weed management in Arkansas crops and the growing resistance of agricultural weeds to existing herbicide chemistries. The experiment station is the University of Arkansas System Division of Agriculture’s research arm.
The results of the field trial indicate that the system can offer a short return on investment at the lowest sensitivity setting and allows for a 43% to 59% reduction in herbicide use compared to broadcast applications, in which herbicide is applied across an entire field.
Settings are Key
At higher sensitivity settings, the See & Spray system is less selective about what it sprays when applying herbicide, resulting in more herbicide used. At low sensitivity settings, the system sprays fewer potential weeds and uses less herbicide, but a greater number of weeds are present at harvest.
“When a grower lowers the sensitivity setting, only larger weeds are sprayed, which will result in a reduction in herbicide use in the short term,” Norsworthy said. “However, when subsequent applications within a year are made, those pigweeds missed with the first application could not be controlled in the follow-up application. These escapes produced seed, resulting in an increase in the soil seed bank.”
In the experiment station’s field trial, operating at a low sensitivity setting increased the Palmer amaranth pigweed population by 280% each year.
When the low sensitivity setting was used, researchers observed a slight yield increase of about four bushels of soybean per acre — likely the result of reduced injury to soybean plants from herbicide applications — but it came with a significant increase in Palmer amaranth pigweed.
Based on the long-term results, Arkansas soybean producers could expect herbicide cost savings from 13% to 80%, which would net $1.6 million to $48 million per year on post-emergence herbicide expenditures in Arkansas, the study noted. If using the technology improperly, however, the 280% increase in pigweed each year could result in accelerated herbicide resistance or additional in-season applications, costing Arkansas producers upwards of $60 million per year based on an average cost of $20 per acre for post-emergence herbicide.
How it Works
See & Spray uses visual recognition and machine learning to selectively spray pesticides in crop fields rather than broadcasting chemicals over an entire area.
A series of digital cameras mounted on 120-foot booms affixed to a tractor are used to identify and spot-spray weeds. The original concept was developed by Blue River Technology in California to thin lettuce fields to an ideal plant population. When John Deere acquired Blue River about eight years ago, the concept was expanded to identify and eradicate weeds in row crop agriculture.
For the study that began in 2022, Norsworthy used a See & Spray prototype to measure the year-to-year effects of using single-tank applications that apply both post-emergence and pre-emergence herbicides, also known as residuals.
For his trials, Norsworthy used the Agricultural Test Machine from Blue River, which is a scaled version of the See & Spray Ultimate with dual tanks that allow for broadcast applications of residuals and targeted applications of post-emergence herbicides. By running it as a single tank system, however, he can simulate the See & Spray Premium, which he said is more affordable and the more widely adopted option in Arkansas.
The single-tank and boom system for the Premium model requires producers to either apply residual herbicides through the targeted See & Spray or make two separate passes, where one is for targeted applications of post-emergence herbicides, and the other is a broadcast of the residual herbicides.
Highs and Lows
Norsworthy compared broadcast applications to targeted applications at the lowest and highest spray sensitivity settings. Efforts were prioritized on herbicide savings, weeds present and missed at application, reproductive weed escapes at harvest and grain yield.
At the highest sensitivity setting, targeted spray applications were generally comparable to the standard broadcast application, Norsworthy said. Targeting both residual and post-emergence herbicide chemistries offered the highest return on investment with the See & Spray system, minus the seed bank increase when targeting residuals at a low sensitivity setting.
“All of my data would indicate that using the high-sensitivity setting is best in most scenarios,” Norsworthy said. “If the Ultimate is being used, the residual can be broadcast and the post-emergence herbicide can be targeted. If a Premium is used, the growers need to make multiple passes.”
Norsworthy said his previous studies have shown broadcasting residual herbicides was more effective in controlling weeds than targeting “and in most cases, there are subsequently more weeds present when the residuals are targeted.” At planting, residual herbicides ideally need to be broadcast, he added, “and then the post-emergence herbicide would be targeted.”
Return on Investment
The See & Spray Ultimate can run at 15 miles per hour, but Norsworthy expects the high speed to increase. The maximum speed for the Premium model is about 12 miles per hour. Most of Norsworthy’s small-plot research was done at 8 to 12 miles per hour since he said it is challenging to get a sprayer up to 15 miles per hour without having extremely long fields.
Tristen Avent, Norsworthy’s Ph.D. student in the crop, soil, and environmental sciences department, has been working on economic analyses and breakeven points for the use of both the Premium and Ultimate models.
When assuming a $25,000 See & Spray upgrade cost from a comparable John Deere sprayer and incorporated applicator efficiency, Avent said the high sensitivity setting saved $30.49 per acre over the entire season and posed no increased risk relative to the broadcast method.
If used at both early- and mid-post-emergence in a single season, the buyer could expect the sprayer to pay for itself after treating 819 acres for a $25,000 upgrade or 2,460 acres for a $75,000 upgrade.
For the calculations, Avent said they follow the American Society of Agricultural and Biological Engineers Standards to incorporate machine costs and speed. Avent and Norsworthy are also working with Lanier Nalley, head of the agricultural economics and agribusiness department, to determine the per-acre cost dynamics and produce a variety of scenarios for producers to consider, including ways to use See & Spray, machine and herbicide costs, and efficiency in different crops.
This information is provided by the University of Arkansas System Division of Agriculture
Arkansas Agricultural Experiment Station.
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