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Funded Project

Funding Program: IPM Enhancement Grants

Project Title: Cover Crop Interseeding to Manage Herbicide-Resistant Weeds

Project Directors (PDs): Erin Haramoto [1] Tim Phillips [2]

Lead State: KY Lead Organization: University of Kentucky

Undesignated Funding: $27,921

Start Date: Mar-01-2016 End Date: Feb-28-2017

Pests Involved: Marestail

Site/Commodity: soybeans

Area of Emphasis: integrated weed management

Summary: This project explores a potential solution to a practical challenge of using cover crops as part of an integrated weed management program. Such integrated programs contribute to the management of herbicide resistant weeds, which are major problems in grain crop production in Kentucky and throughout the Southern region. Glyphosate-resistant marestail is now widespread in the south and is very difficult to control in no-till soybeans. This weed traditionally emerges in the early spring, though cohorts of fall emerging marestail have been noted recently in Kentucky and other Southern states, necessitating additional fall herbicide applications. Integrating cover cropping with good chemical control may contribute to management of this species (and other winter annuals) as marestail is sensitive to competition when small. However, there are challenges to integrated management of this weed. Timing of cover crop establishment relative to weed emergence is critical. Cover crops are typically drilled after cash crop harvest. Depending on residue cover, soil moisture, and ambient temperature, cover crop establishment and early growth may be limited severely in the fall and ground cover may be slow to develop. If marestail emerges prior to or soon after harvest, it may be well-established by the time the cover crop is established and may not be effectively out-competed. Cover crop interseeding is a technique in which cover crop seed is sown into a standing cash crop. A modified grain drill that plants cover crops into corn when it is about 1 tall has been developed by researchers and extension agents in Pennsylvania. Since seeds are sown directly into the ground, establishment is less reliant on soil moisture conditions than broadcast seed. Establishing cover crops in this way may improve their competitive ability against weeds, help further protect soil from erosion as continuous ground cover is maintained, and improve excess nutrient capture. This proposal seeks to generate baseline data on this approach in the Southern region. We also seek to draw on the expertise of the forage breeding program at the University of Kentucky to identify cover crop species that are suited to Kentucky and will work well when interseeded (e.g. they are shade tolerant and have low moisture requirements to limit competition with the cash crop). This technique is a great example of Integrated Pest Managementa science-based approach to pest management that addresses environmental, economic, and human health concerns through the potential reduction in herbicide use and improvements in the overall sustainability of weed management. If this technique proves viable in Kentucky, it could reduce or eliminate the need for fall burndown herbicide applications if winter annual weeds are successfully managed by an early-established competitive cover crop stand; contribute to managing glyphosate-resistant fall-emerging marestail and other herbicide resistant winter annuals weeds; and improve delivery of other ecosystem services provided by winter cover crops, including excess nutrient capture, soil erosion prevention, and maintenance of soil organic matter levels. Objectives: Outputs: " Experimentally demonstrate interseeding as a viable option for establishing cover crops into standing grain cash crops in Kentucky " Collect baseline data on cover crop interseeding in the Southern region, including cover crop establishment, competition with corn crop, and over-wintering " Collect baseline data on interseeded cover crops ability to suppress marestail and other winter annual weeds " Collect baseline data on how different species and cultivars adapted to Kentucky respond when interseeded into a corn crop " Demonstrate interseeder unit in late-planted corn (for demonstration purposes only) at Corn, Soybean, and Tobacco Field Day in Princeton, KY (July 2016) and show interseeded cover crop stand in experiments Outcomes: " Increased awareness and eventual adoption of interseeding " Change in existing knowledge base about interseeding in this region " Change awareness of cover crops as a tool for managing winter annual weeds " Expand list of options that are available for interseeding " Grower innovation around interseedinguse of regionally-adapted varieties, integration of grazing, cutting for forage, other region-specific activities " Baseline data used to leverage AFRI grant

Final Report:

Outcomes Outcome 1, learning: * We were not able to demonstrate this technique and these experiments at the field day due to stormy weather. * We will collect data on baseline knowledge about this technique as we begin to survey Kentucky growers about cover cropping Outcome 2, action: * To our knowledge, there has not yet been changes in action that have resulted from this project. Outcome 3, condition: * To our knowledge, there has not yet been a change in condition as a result of this project.

Outputs Output 1, Activities: * Research activities— *Planted corn, applied herbicides to subplot treatments in one experiment, interseeded cover crops in both experiments *Collected data on cover crop establishment, weed community, and corn development *harvested corn and drilled cereal rye as an additional treatment in one experiment *continued with data collection on weed community, cover crop survival over winter *terminated cover crop and planted soybeans in both experiments * Corn, Soybean, and Tobacco Field Day (July 28, 2016) *attempted to demonstrate interseeder and highlight research trial, but field day was held indoors due to stormy weather *trial was discussed in talk on the use of cover crops to suppress weeds Output 2, Publications: * none yet Output 3, other products and services: * annual ryegrass and orchardgrass both established well, but the stand of both declined over the hot, dry summer * by the spring of 2017, cereal rye drilled after harvest produced the most biomass. Orchardgrass produced intermediate amounts of biomass, while annual ryegrass did not produce much biomass. * where interseeded cover crop stands were adequate, the ground was covered most of the winter. However, thin stands led to much bare soil * some of the other entries tested showed promise, though none produced as much biomass as orchardgrass * corn yield was not affected by the interseeded cover crops * weed biomass at corn harvest was similar in all cover crop treatments. The following spring, weed biomass was lowest in plots with cereal rye, intermediate in plots with orchardgrass, and highest in those with annual ryegrass or no cover crop Output 4, Ways you publicized your project: * Aside from the field day, this project was publicized at the PI’s departmental two-year review seminar Output 5, secured funding for further projects: * Kentucky Soybean Promotion Board, Optimizing winter cover crops for weed management in soybeans, $39,993, 7/1/17-6/30/18 * USDA-NIFA, Optimizing cropping systems for resilience to stress: role of maturity group selection and cover crops on yield, weeds, insects, and microbes (Awarded to University of Nebraska, Ohio State University, and University of Kentucky), $461,187; University of Kentucky portion is $110,640, 3/15/17-2/28/19 Output 6, unsecured funding for further projects: * USDA-NIFA (Crop Protection and Pest Management), Integrated management techniques to combat potential shifts in horseweed emergence, application completed and submitted May 2017, $324,992 requested * Southern Sustainable Agriculture Research and Education (SARE), Integrating livestock into cropping systems: cover crop grazing in corn/soybean rotations, pre-proposal completed and submitted June 2017, $300,000 requested Output 7, incomplete objectives: none

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