Interseeded Cover Crops in Corn: Can interseeding a cover crop provide enough forage to offset cover cropping costs?

Key Project Details

• Interseeding allows for early cover crop establishment and growth, having the potential to provide sufficient forage to offset costs.
• Evaluate the effect of interseeding a cover crop of your choice on forage inventory, soil protection, corn yield and overall profitability.
• Project includes a routine soil test, cover crop sampling and forage quality analysis (estimated minimum budget: $230 per field), with option to include additional expenses, sampling costs, and incentive payments in the budget.
• Interested in taking a deeper dive into interseeding cover crops? This project includes optional research packages so farmers can further explore topics that support management decisions on their farms. They include opportunities to investigate soil nutrients, pest pressure, interseeding comparisons, corn row spacing, or second-year interseeding impacts.

Project Background

Interseeding is a method used to establish cover crops earlier in the growing season by planting cover crops when corn is still growing.

While it may overcome barriers related to cover crop establishment following corn harvest and allow for improved biomass production, investigating this practice will improve our understanding of interseeding benefits, tradeoffs and strategies for successful implementation.

This research trial aims to address the question, “Can interseeding a cover crop provide sufficient forage to offset any cover cropping costs?”, while collecting insights from participating farmers on challenges they face and how they are managing their cover crops to find success.

As a collaborative producer-led research trial, results will provide relevant insights for your operation and contribute to a wider effort to support the advancement of conservation throughout the state.

Why Participate?

Learn through data from your farm! See how interseeding works on your farm and what it means for your conservation goals and profitability. Interested in taking a deeper dive into interseeding cover crops? The project includes optional research packages to tailor the project to your goals.

Connect with other participating farmers to hear what they are trying, how your results compare, and where others are finding success with interseeding cover crops.

Contribute to a larger effort to support farmer-led conservation solutions and resources that can benefit other Wisconsin farmers. Results from this project will be aggregated, analyzed, and shared to support other farmers with successful interseeding.

Interseeded Cover Crops in Corn: Farmer-Led Research Project Summary

What will I learn?

The project evaluates the effect of interseeding a cover crop on crop yield, forage inventory, soil protection and economic return. Participating farms are encouraged to investigate cover crop species and interseeding methods that are relevant to their goals and operations to support farmer-driven interseeding insights.

Baseline Requirements

Treatments: Compare an interseeded cover crop and a “no cover crop” control

Layout: a minimum of three replicates is recommended (i.e., repeating interseeded cover crop and no cover crop strips at least three times in the field)

Data collection: routine soil test, cover crop biomass & forage quality, and corn yield

Tailor to your goals: Take a deeper dive into interseeded cover crops with optional research packages to better support management decisions on your farm. Investigate soil nutrients, pest pressure, interseeding comparisons, corn row spacing, or second-year interseeding impacts.

Field and Management Considerations

This project can be implemented on any corn field and management decisions on cover crop management, fertilizer, herbicides, etc are up to the participating farmer, but should be consistent across the entire trial (i.e., the plots should be treated the same except for the interseeding).

Participants are encouraged to select cover crop species, seeding rate, and method (ex: broadcast via drone, spreader, drilled, etc) that are most relevant to their goals and operations.

We recommend that cover crops are interseeded earlier in the season (V2-V7 growth stage) to provide sufficient time for cover crop forage production.

Interseeding cover crops can be challenging for fields with high weed pressure and requires special attention to herbicide products and their residuals, cover crop species selection, and timing for successful cover crop interseeding. Planning and discussing with our team or your agronomist are recommended for the best results.

Extension’s on-farm research team is here to assist along the way. For those participating in the project, you will receive technical support with setting up the trial, implementing it, and collecting relevant data. General guidance on trial layout and data collection is included below as you consider this project, but more details and technical support will be provided directly to those participating.

Trial Layout

Our goal is to keep producer-led research trials simple and practical for participating farmers. Including multiple “test strips” in a field can provide an accessible way to implement these trials while still providing quality data to address the objectives of this project.

In particular, since yield is inherently variable even under the same management, replicating treatments is a way to confidently understand if any difference in yield is due to the interseeded cover crop rather than just natural variability.

Trial Layout Recommendations

Replicating (i.e., repeating) each treatment at least three times

Plot dimensions: Full-field test strips that are at least three widths of the combine will be easiest for harvest data collection. If using a yield monitor, plots or test strips should be a minimum of 350ft for yield monitor accuracy.

Consider cover crop seeding equipment when developing a trial layout. If drone seeding, work with the drone operator to achieve a good swath width for the cover crop seed and trial layout.

Example layouts are below, but we can work together to set up a trial that works for you, your fields, and equipment.

Timeline

Time of Year	Project Activities
Winter	Planning: select field, trial layout, cover crop species, and herbicide plan
Spring Before Harvest	Routine soil test Corn planting
In-Season	Interseeding (recommend when corn is V2-V7): including interseeded cover crop and no cover crop comparison strips – Take photos and observations of residue and field conditions Field visits, observations & photos. Key times include: at cover crop planting, 30 days after planting, mid-season, and prior to harvest.
Pre-Harvest	Prepare for harvest data collection (organize for a weigh wagon, scales, or calibrate yield monitor) Harvest and record yield data for each cover crop and no cover crop strip
Late Fall	Fall cover crop sampling, photos & forage quality analysis (prior to killing frost) Complete field history, management, and trial observation survey. Share field and lab results for analysis. Discuss individual & project-wide results
Spring After Harvest	Recommended for overwintering cover crops Spring cover crop sampling, photos & forage quality analysis (prior to termination)

Data Collection for this Project

Field measurements, farmer-reported management information, and any observations are used to meet the objectives of this trial, interpret individual trial results, and support wider recommendations developed from research results.

• Routine soil test
• Cover crop sampling and forage quality: including photos, cover crop biomass & forage quality
• Corn yield: using a calibrated yield monitor, weigh wagon, or scales
• Field management data (including field history, management details, and any other observations)
• Optional data: explore optional research packages or discuss with our team if there are other measurements you are interested in.

Participants will receive data collection sheets and guidance on submitting data, which will be analyzed and summarized into a research report by UW-Madison Extension. At the end of the season, participants and partners will review and discuss individual results and connect with other participants about project-wide results.  

Budget Considerations

Groups are encouraged to budget for this project to best meet their goals and priorities. All projects should budget for a routine soil test, cover crop forage quality analysis (fall and spring, if applicable), shipping of samples, and any sampling equipment.

For a trial with three replications, the estimated cost for the minimum required data collection is $230 per trial. Given that analysis fees are subject to increase, groups are encouraged to reach out to their lab of choice for up-to-date costs.

In addition, groups are encouraged to budget for any additional expenses they wish to cover. This may include farmer participant stipends or incentive payments, labor for trial set-up or sampling, mileage, cover crop seed and management expenses, field day activities, or other additional measurements. Any questions on eligible costs can be directed to the specific grant or funder, if applicable.

Optional Research Packages

Interested in taking a deeper dive into interseeding cover crops into corn? Tailor this research trial to answer your interseeding questions by adding one or more of the below options to the baseline project: 

Interseeded Cover Crops and Nutrient Dynamics

Track soil nutrients and/or cover crop nutrient uptake to evaluate nutrient dynamics for your field and conditions. Add on any of the following measurements to better address your questions.

• Low effort: requires additional soil or plant sampling
• Soil nitrate and ammonium: Did the interseeded cover crop impact soil nitrogen availability throughout the season or residual nitrate following corn, which would otherwise be at risk of leaching? Measuring soil nitrate and ammonium throughout the season can provide insights to better understand potential water quality benefits, yield impacts and future nitrogen management considerations.
• Soil samples are taken for each interseeded cover crop and no cover crop test strip throughout the season: in-season (0-1’), post-harvest (0-1’, 1-2’), in the fall prior to the first winter freeze (0-1’, 1-2’), and, for overwintering cover crops, spring pre-plant (0-1’, 1-2’). (estimated budget for additional sampling is $750 per trial).
• Other soil nutrients: Did the interseeded cover crop impact other soil nutrient levels? Add-on other soil nutrient packages of your choosing (ex: routine, Haney, etc). Soil samples are taken for each interseeded cover crop and no cover crop test strip after corn harvest and prior to the first winter freeze.
• Cover crop nutrient uptake: How much nutrients did the cover crop take up? Analyze cover crop nutrient concentrations prior to the first killing frost or termination. (estimated budget for additional sampling is $150 per trial)

Interseeded Cover Crop and Pest Pressure

Evaluate pest pressure throughout the season to better understand the benefits and risks of integrating cover crops.

While cover crops have the potential to suppress weed pressure, there are unknowns of how other pests, like slugs, respond in high-residue conservation cropping systems. Evaluating weed, slug, and other observational pest pressure across the interseeded cover crop and no cover crop treatments can provide insights on how cover crops can be an effective pest management tool for your operation.

• Low effort: requires additional in-field assessments and observations throughout the season
• Visual assessments of weed pressure and early-season slug monitoring will be conducted in each cover crop and no cover crop test strip. Slug monitoring requires weekly visits to count slugs on the traps (visit SlugNet for more information).
• No additional sampling costs if participants register through SlugNet to receive supplies for no additional cost.

Interseeded Cover Crop Comparison

Explore different cover crop species, varieties, seeding rates, or interseeding approaches to fine-tune interseeding for your system and goals.

This project compares three treatments:

1. No cover crop (the “control”)
2. Interseed cover crop #1
3. Interseeded cover crop #2 on corn yield, cover crop biomass, and forage quality.  

• Medium effort: requires additional cover crop treatment and sampling for both cover crops in the fall and spring, if projects include overwintering cover crops.
• Examples of interseeding cover crop comparisons include:
  • Cover crop species (ex: single vs. multispecies mix)
  • Cover crop varieties of the same species
  • Seeding rate
  • Interseeding method (ex: drone vs. drill)
  • Interseeding timing
• Estimated budget for required sampling: $460 per trial for routine soil test and forage quality analysis for both interseeded cover crops in the fall and spring (if cover crops overwinter).

Corn Row Spacing and Interseeding Cover Crops

Explore how corn row spacing impacts interseeded cover crop performance, forage inventory, and profitability.

• High effort: requires two corn row spacings (e.g., 30 in. vs. 60 in.) in addition to the interseeded cover crop and no cover crop treatments.
• Trial layout: balancing an additional management practice can be challenging in an on-farm research trial, and recommended trial layout will be dependent on your equipment, interseeding method, field, and preferences.
• Estimated budget for required sampling: $460 per trial for routine soil test and forage quality analysis for both interseeded cover crops in the fall and spring (if cover crops overwinter).

Interseeded Cover Crop Impact on Following Crop

Does the interseeded cover crop impact the following year’s crop?

• Medium effort: requires maintaining interseeded cover crop test strip locations and yield data collection for the following year’s cash crop.
• No additional sampling costs

Unsure if this project is right for you? Reach out to our team for more information on what you will learn, how to implement the project, or how to budget for it in an upcoming grant.

About Collaborative Producer-Led Research and Demonstration Projects

This project is a collaborative effort of Wisconsin farmers, DATCP’s Producer-Led Watershed Protection Grant Program, UW-Madison Division of Extension, and many local partners and collaborators to support producer-led research, demonstration, and education. Protocols are designed with producers to support farmer-driven conservation solutions, farmer-to-farmer learning, and coordinated data on conservation practice performance across Wisconsin.

Thank you to the Farmer Working Group for their support in developing this protocol.