2019
Multi-Applications of Dicamba on Non-Dicamba Tolerant Soybeans
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Contributor/Checkoff:
North Dakota Soybean Council
Category:
Sustainable Production
Keywords:
AgricultureCrop protectionHerbicide
Parent Project:
This is the first year of this project.
Lead Principal Investigator:
Paulo Flores, North Dakota State University
Co-Principal Investigators:
Project Code:
QSSB
Contributing Organization (Checkoff):
North Dakota Soybean Council
$27,111
Institution Funded:
North Dakota State University
$27,111
Brief Project Summary:

Since the release of dicamba tolerant soybeans, many fields have been affected by growth regulator symptoms, and the trait has since faced heavy regulatory scrutiny. While dicamba symptoms readily affected fields previously, it is unclear how much yields were impacted from injury. This project was created to track the extent of damage from injury to yield; to determine if symptoms can be measured accurately through remote sensing; and to test the validity of plant tissue tests in confirming dicamba application, and identify any changes to subsequent seed viability.

Key Benefactors:
farmers, agronomists, applicators, extension specialists

Information And Results
Final Project Results

Update:

View uploaded report Word file

Research Conducted
A herbicide drift study was conducted to test microrates of dicamba on conventional soybean performance. Spectral data were collected to test methods for visualizing dicamba injury in a field. Images were analyzed with four different vegetation indices.
These data were prepared for presentations at the Wild World of Weeds Workshop and Western Society of Weed Science. These data were also published in the CREC Annual Report and on Twitter (@agronomizeNDSU).
Why the Research is Important to ND Soybean Farmers
Soybeans are inherently extremely sensitive to dicamba. This project was created to track the impact of injury to yield, determine if symptoms can be measured with an aerial image, and identify any changes to subsequent seed viability.
While dicamba symptoms readily affected fields in 2017 and 2018, it is less clear how much yields were impacted as a result of the injury. In many cases injury appeared with little to no observed yield loss, but not true in other instances. Local data is important here to demonstrate realistic yield and quality expectations once visual symptoms are observed.

Final Findings of the Research
Only the highest rate of dicamba, with and without glyphosate, reduced yield (Table 1). That same rate also caused an extreme delay in plant maturity where the plants only matured due to frost. Even with up to 25% injury to the plants, the yield was not reduced, similar to previous years’ work.
Vegetation indices were analyzed by comparison to visual injury and yield 20 days after herbicide application. The relationship between visual symptoms and analyzed imagery was strong. Among the indices used, NDVI, NDRE, and GNDVI all generated nearly identical relationships to yield and injury. The Excess Green (ExGr) index had a consistently lower correlation, however, the relationships were still good.

Benefits/Recommendations to North Dakota Soybean Farmers and Industry
Dicamba symptoms do not dictate a decline in soybean yield. One of the keys is whether the growing points remained healthy. Affected plants were still shorter, but continued to grow. The highest dose caused severe stunting and no new growth until late in the season. There was no loss of germination due to any dose of dicamba tested.
Aerial images appears to be suitable for measuring dicamba injury. The Excess Green index, which was calculated from a color image with a Phantom 4 Pro, could be used to quantify the area affected by dicamba injury.

The United Soybean Research Retention policy will display final reports with the project once completed but working files will be purged after three years. And financial information after seven years. All pertinent information is in the final report or if you want more information, please contact the project lead at your state soybean organization or principal investigator listed on the project.