Project Details:

Title:
Fall-Seeded Cover Crop Tolerance to Soybean Herbicides

Parent Project: Fall-Seeded Cover Crop Tolerance to Herbicides
Checkoff Organization:North Dakota Soybean Council
Categories:Crop management systems, Weed control, Sustainability
Organization Project Code:QSSB
Project Year:2020
Lead Principal Investigator:Greg Endres (North Dakota State University)
Co-Principal Investigators:
Michael Ostlie (North Dakota State University)
Keywords:

Information and Results

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Project Summary

ND crop acreage that includes cover crops appears to be rapidly expanding due to benefits including reduction in soil erosion, soil moisture management, weed suppression, and long-term improvement in soil productivity. Management and input costs are involved with incorporating cover crops into a cropping system, that normally includes soybean. Information to assist with successful establishment of cover crops would be beneficial to farmers. A risk often overlooked is herbicide residual that can greatly reduce cover crop stands. This study will provide information that will help soybean farmers successfully establish cover crops in the fall following soybean production. The information on tolerance of selected cool-season cover crops to commonly used soybean herbicides with soil residual will be widely available and useful for ND farmers and crop advisers.

Project Objectives

Document the tolerance of selected fall-planted cover crops following the normally timed application of soybean PRE- and POST-applied herbicides that have soil residual. Data will be compiled across several site-years to generate a reference table published in the ND Weed Control Guide (NDSU Extension circular W253).

Project Deliverables

Progress of Work

Updated November 25, 2019:
Completed work:
• Fargo, 2019: Trial was successfully established. Soybean were planted late May followed by application of soil-applied herbicides (metribuzin, sulfentrazone, flumioxazin, pyroxasulfone, and imazamox) and POST herbicides (dicamba, fomesafen, imazamox, and glufosinate) at labeled rates for soybean. Soybean were terminated by mowing late August. Cover crops (turnip, lentil, radish, flax, field pea, winter rye, and barley) were planted perpendicular to herbicide strips on September 6. Due to excessive fall rain (September=4.2 inches; October=3.5 inches), the trial was partially flooded and abandoned as viable data could not be generated.
• Carrington, 2019: Trial was conducted at the Research Extension Center. Soybean were planted May 20 followed by application of soil-applied herbicides [metribuzin (Sencor), sulfentrazone (Spartan), flumioxazin (Valor), pyroxasulfone (Zidua), and imazethapyr (Pursuit)] on May 21 and POST herbicides [dicamba (Engenia) and fomesafen (Flexstar)] on June 18. Soybean (R5-6 growth stage) were terminated by mowing on August 20. Cover crops (turnip, radish, flax, field pea, winter rye, and barley) were planted perpendicular to herbicide strips August 30. Cover crops were visually evaluated for plant injury (plant biomass/stand reduction) on September 20 and October 9.
Preliminary results:
Carrington: Field pea was tolerant of all herbicides. All herbicides caused injury to select cover crops. Plant injury exceeding 10%: barley = Valor; rye = Zidua; flax = Sencor; radish = Sencor, Spartan, Zidua and Flexstar; and turnip = Sencor and Zidua.
Work to be completed:
• Research reports written and published in ‘2019 ND Weed Control Research’ and ND Soybean Council annual research report.
• Data to be presented during 2020 NDSU Weed Workshop (January; Fargo) and other NDSU Extension soybean production and cover crop meetings and tours. Research paper to be tentatively presented in March, 2020 at Western Society of Weed Science annual meeting.

Final Project Results

Updated June 18, 2020:

View uploaded report Word file

Fall-seeded cover crop tolerance to soybean herbicides
Why the research is important to ND soybean farmers:
The goal of this project is to build a NDSU database on late-season planted cover crop tolerance to early season applied soybean herbicides that have soil residues. This database will aid farmers and crop advisers as plans are made for adding cover crops into their cropping system.

Research conducted:
• Carrington, 2019: ‘AG03X7’ soybean were planted May 20 followed by application of soil-applied herbicides (Pursuit, Sencor, Spartan, Valor and Zidua) on May 21 and POST herbicides (Engenia and Flexstar) on June 18. Soybean (R5-6 growth stages) were terminated by mowing on August 20. Cover crops (turnip, radish, flax, field pea, winter rye, and barley) were planted perpendicular to herbicide strips August 30 and evaluated for plant injury on September 20 and October 9.
• Fargo, 2019: Soybean were planted; soil- and foliar-herbicides applied; and cover crops were planted September 6. However, data was not generated from the trial as it was abandoned due to fall flooding.
Research findings:
• Carrington: All herbicides caused cover crop injury (biomass and/or stand reduction). Field pea was tolerant of all herbicides. Plant injury >20% occurred with radish and turnip from Sencor, and radish from Spartan and Zidua.
Benefits/Recommendations to ND soybean farmers and industry:
Research reports for the Carrington trial was written and published in ‘2019 ND Weed Control Research’ (www.ag.ndsu.edu/weeds/nd-weed-control-research). After field study is tentatively completed in 2020, a table will be published in ‘2021 ND Weed Control Guide’ as a reference for farmers and crops advisers when selecting cover crops for fall establishment following soybean. This database will aid in successful establishment of fall cover crops, which will reduce soil erosion, help manage soil moisture, increase long-term productivity of soil, plus other benefits.

Benefit to Soybean Farmers

If farmers are including cover crops in their farm management plans, the data generated from this study will aid in increasing their success with establishing cover crops following soybean production. By increasing the potential to successfully establish cover crops, this provides the benefits of a fall cover crop that includes reducing soil erosion, increasing long-term soil productivity, soil water management, reducing weed competition, etc. The information gained from the data will aid farmers in correctly selecting cover crop species after herbicide application in soybean. Extra costs of replacement seed and replanting will be avoided by proper cover crop selection. Effective establishment and use of cover crops will aid in a more sustainable environment for soybean and other crop production.

Performance Metrics

Project Years