Progress report for ONC25-162
Project Information
Growing cover crops (CCs) after corn harvest can be challenging due to Wisconsin’s short post-harvest growing season. Interseeding CCs into corn has gained the interest of row crop and dairy/livestock producers as a method to establish CCs earlier. In addition to soil health benefits provided by CCs, there are opportunities to utilize CCs as an alternative forage crop. Grazing and harvesting don't necessarily compromise other ecosystem services of CCs and can help make them profitable. However, as with many conservation practices, on-farm research and demonstration (R&D) is necessary to overcome interseeding management hurdles and promote adoption.
This proposal seeks to build and support a coordinated R&D network between Wisconsin’s producer-led watershed groups (PLWGs) to advance cover crop interseeding. This project will identify best management practices for broadcast-interseeding CCs into corn using drones, assess the impact that interseeded CCs have on corn yield, measure CC biomass and forage quality, and determine if the forage produced has an economic value that may compensate for possible increased costs. Importantly, this pilot project will empower the PLWG program to assess whether conducting coordinated research across watershed groups adds value to the program’s overall mission and future direction.
- Quantify corn yield and measure soil health parameters in conventional and CC interseeding systems on eight farms in four Wisconsin watersheds.
- Measure CC biomass and forage quality. Determine if using CCs as an alternative forage has economic value that may compensate for increased costs incurred or corn yield drag.
- Hold field days at collaborator farms during CC interseeding and post-corn harvest to encourage peer-to-peer learning and successful farmer-led leadership.
- Report project results via the PLWG’s website, Extension articles, and at PLWG meetings.
- Develop a model of coordinated PLWG R&D projects that collaboratively address questions about sustainable agricultural practices in Wisconsin.
Cooperators
- (Educator and Researcher)
- (Educator and Researcher)
- (Educator and Researcher)
- (Educator and Researcher)
Research
Background
The short and unpredictable growing season following corn harvest in Wisconsin and the Upper Midwest can make it challenging to establish and grow cover crops, leaving many fields without living cover through late fall and spring. Interseeding cover crops into standing corn is a practical alternative because it moves seeding earlier in the season, increasing the chance of establishing cover and producing biomass after corn harvest. This approach aligns with sustainable agriculture goals by reducing fallow periods that can contribute to erosion and nutrient losses while supporting longer-term soil health improvements.
Despite growing producer interest, interseeding adoption is constrained by uncertainty about best management practices under Wisconsin conditions. Seeding method is a key barrier: many interseeding options require ground equipment to pass through a growing crop, which can cause crop damage and contribute to soil compaction, particularly when soils are wet. Drone-based broadcast seeding is a newer approach in the region that can address these constraints by enabling seeding during narrow windows and in field conditions that limit ground equipment, while avoiding wheel traffic through standing corn. Drone “prop-wash” may also improve seed-to-soil contact relative to some conventional aerial broadcast applications, potentially supporting more consistent establishment.
Interseeding timing also involves tradeoffs. We initially focused on early interseeding during corn vegetative stages (V3–V7) to establish cover crops before canopy closure and extend the effective growing window. Early seeding, however, can be limited by soil moisture at planting, herbicide compatibility, and the risk of corn-cover competition when conditions favor rapid cover crop growth. During discussions with farmers, a subset of participants were interested in later interseeding during corn drydown for reducing competition with corn and avoiding herbicide residual constraints. Generally, earlier vegetative interseeding can enhance fall establishment in some contexts, while late interseeding can improve subsequent spring biomass for winter-hardy species. Because these tradeoffs directly affect producer decisions, we broadened the scope slightly to explore both early and late interseeding timings with the group to generate more practical, locally relevant guidance.
Finally, while cover crops provide conservation benefits, they also add direct costs for seed, planting, and termination, and producers may be hesitant without clearer short-term returns. Evaluating interseeded cover crops as a value-added forage resource alongside agronomic and soil health outcomes can help determine whether forage value can offset potential costs and reduce adoption risk for grain farmers.
Methods
On-farm strip trials were conducted at eight locations across Wisconsin, spanning multiple corn-producing regions and four producer-led watershed group areas. Field sites were selected by cooperating farmers and strip dimensions were scaled to the width and length of each farm’s equipment. Farmers made all routine crop management decisions (e.g., hybrid, fertility, pest management, and harvest operations), while project personnel coordinated cover crop treatments and standardized measurement protocols across farms. Corn was planted in 30-inch rows in early May (exact dates varied by farm; 5/8-5/16) at populations ranging from 28,000- 32,000. All farms have been using cover crops and reduced/no-tillage for years. All fields that participated in this study were no-till fields.
The primary comparison at all locations was corn with no interseeded cover crop (control) versus corn with a cereal rye cover crop interseeded by a drone (60 lbs/ac) at the V4 corn growth stage (26-May to 12-June depending on farm). A subset of five farms also implemented a late-interseeding treatment where cereal rye was interseeded (60 lbs/ac) into corn at corn physiological maturity (R6; 3-September to 16-September) to compare early- versus late-interseeding strategies. To reflect farmer interest and operational goals, additional species treatments were implemented at select farms, including annual ryegrass (13 lbs/ac) at two farms, triticale (60 lbs/ac) at one farm, and a multi-species mix (red clover (30%), radish (25%), turnip (15%), dwarf essex rape (15%), trophy rape seed (15%)) at one farm. Drones were used to interseed all cover crops.
Trials were established as replicated strip trials in a randomized complete block design with 2–4 replications (most commonly 4) depending on farmer preference and spatial constraints. Strip length varied among locations based on each farmer’s equipment and field dimensions and ranged from 200 to 500 ft. Plot widths varied due to similar factors and ranged from 40 to 60 ft. In total, 27 control replications and 27 V4 cereal rye interseeding replications were established across sites. A subset of farms also established a late-interseeding cereal rye treatment (n = 15). Additional farmer-selected species trials included V4 annual ryegrass (n = 5), a V4 multi-species mix (n = 4), and V4 triticale (n = 1; demonstration).
Prior to interseeding, soil samples (0-6") were collected as field-level composite samples from each field to establish baseline values for microbial respiration, aggregate stability, and basic fertility (including SOM and pH).Follow-up soil sampling by treatment and replication will occur in spring 2026 to assess any short-term treatment effects on microbial respiration, aggregate stability, or basic fertility.
Plots were assessed for cover crop emergence, establishment, and percent cover (estimated using Canopeo) approximately 30 d following V4 interseeding. Following corn harvest, cover crop aboveground biomass was sampled using three 2-ft² quadrats randomly located within each strip. Cover crop height was measured from 5 plants in each quadrat. Biomass was clipped at the soil surface, weighed in the field to quantify biomass production, and submitted to an analytical lab for forage quality analysis. Percent dry matter was used to convert fresh biomass weights to dry matter (DM) biomass. Cover crop height was also recorded and percent cover was estimated using Canopeo.
Corn grain yield was collected at harvest (30-October to 18-November depending on farm) for all treatments using on-farm yield monitors (calibrated by farmers according to their standard practices) or with weigh wagons. Yield was collected from the full-length treatment strips (excluding headlands), and grain yield was adjusted to 15.5% moisture for reporting and analysis.
Baseline soil health
Baseline soil health indicators varied substantially across the nine sampled fields, reflecting a wide range of starting conditions among participating farms (Table 1). Soil microbial respiration ranged from 19 to 212 ppm (median 81 ppm), while soil organic matter ranged from 2.1 to 6.0% (median 3.8%). Across sites, soil respiration was strongly positively related to soil organic matter (Fig. 1), consistent with expectations that higher organic matter supports greater microbial activity. Soil health benchmarks developed for Wisconsin indicate an average microbial respiration value of 42 (15-62 ppm) for sandy soils and a value of 68 (33-98 ppm) for medium/fine-textured soils (Fig. 2). Soil pH spanned 5.1–7.0, indicating that most sites were near neutral but one field was notably more acidic. Routine fertility metrics were also variable, with Mehlich-3 P ranging from 53–118 ppm and NH₄OAc K from 101–258 ppm.
Table 1. Baseline soil health data summary. SC=South Central WI; NW=Northwest WI; C= Central WI; NC=North Central WI.
| Farm ID* | Region | Soil respiration (ppm) | Soil pH | Organic Matter (%) | Mehlich-3P (ppm)** | NH4OAc K (ppm) | Aggregate Stability |
| 1 | SC | 30 | 6.5 | 2.3 | 107 | 101 | 0.41 |
| 2 | SC | 19 | 6.9 | 2.1 | 53 | 147 | 0.48 |
| 3 | SC | 74 | 5.1 | 3.2 | 58 | 258 | 0.4 |
| 4 | SC | 212 | 6.9 | 6 | 69 | 147 | 0.48 |
| 5 | NW | 81 | 6.2 | 4 | 64 | 239 | |
| 6 | NW | 88 | 6 | 3.8 | 118 | 226 | |
| 7 | C | 25 | 6.8 | 2.5 | 76 | 212 | |
| 8 | NC | 128 | 6.6 | 3.8 | 54 | 137 | 0.43 |
*Sampled fields are identified by arbitrary numbers 1-8 for maintaining anonymity.**Most soil test for phosphorus in Wisconsin are measured in Bray-1 which are usually less than M3.
Cover crop emergence
Table 2. Percent cover approximately 30 DAI for cover crops interseeded into corn grain at the V4 corn growth stage.
| Farm ID | Percent cover (%) | ||
| Cereal rye | Annual ryegrass | Multi-species mix | |
| 1 | 31.68 | - | - |
| 2 | 24.59 | - | - |
| 3 | 39.9 | - | - |
| 4 | 15.52 | 51.52 | - |
| 5 | 20.24 | 16.27 | - |
| 6 | 17.89 | - | - |
| 7 | 27.7 | - | - |
| 8 | 28.9 | - | NA |
Cover crops established at all sites (Table 2). Measured approximately 30 days after interseeding (DAI), cereal rye and annual ryegrass percent cover ranged from 15.52% to 39.90% and 16.27% to 51.52% respectively. There were significant weed escapes at site 7 and V4 cereal rye establishment was spotty.
We calculated total precipitation (inches), daily maximum soil moisture at 2 inches (volumetric water content, %), and daily maximum soil temperature at 2 inches (F) during the interseeding window, which we defined as 7 day before interseeding and 30 DAI (Table 3). Data were collected from the WiscoNet network of weather stations located throughout Wisconsin using the nearest measurement station to each farm. True on-farm conditions may have varied.
Table 3. Total precipitation (inches), average daily maximum soil moisture at 2 inches (volumetric water content, %), average daily maximum soil temperature at 2 inches (F) during the V4 corn growth stage interseeding window.
| Farm ID | WiscoNet station | Average daily maximum soil moisture (%) | Total rain (in) | Average daily maximum soil temperature (F) | Days between cover crop interseeding and corn harvest |
| 1 | Verona | 39 | 7.95 | 77 | 141 |
| 2 | Verona | 39 | 7.95 | 77 | NA |
| 3 | Porter | 36 | 4.79 | 84 | 160 |
| 4 | Arlington | 38 | 5.1 | 69 | 154 |
| 5 | Montana | 35 | 6.29 | 67 | 147 |
| 6 | Montana | 35 | 6.29 | 67 | 147 |
| 7 | Grand Marsh | 11 | 5.54 | 90 | 146 |
| 8 | Marshfield | 47 | 4.62 | 75 | 126 |
Using a drone to interseed cereal rye at the V4 corn growth stage successfully initiated cover crop stands at all farms, but the magnitude and uniformity of emergence was influenced by local conditions. Variability in establishment among farms and cover crop species was consistent with contrasting field conditions during the interseeding window. Across farms, soil moisture ranged from 11-47%, soil temperature 67-90F, and total rainfall 4.62-7.95 in. Consistent with other research from the upper Midwest, rainfall during the interseeding period promoted cover crop emergence. There was, however, still variation in establishment, potentially due to differences in soil moisture and temperature. For example, farm 7 had weed escapes and spotty cereal rye establishment, coinciding with the lowest soil moisture and the highest soil temperature observed during the interseeding window. Farm 3 had the lowest total rain, but still maintained a relatively high percent cover 30 DAI. Baseline soil health indicators also differed widely among fields, indicating variable starting conditions that may contribute to farm-to-farm differences in early cover crop performance.
Late-interseeded (R6 corn growth stage) cereal rye cover crops were assessed after corn harvest. For that subset of farms, we calculated total precipitation (inches), daily maximum soil moisture at 2 inches (volumetric water content, %), and daily maximum soil temperature at 2 inches (F) during the interseeding window (Table 4).
Table 4. Total precipitation (inches), average daily maximum soil moisture at 2 inches (volumetric water content, %), average daily maximum soil temperature at 2 inches (F) during the R6 corn growth stage interseeding window.
| Farm ID | WiscoNet station | Average daily maximum soil moisture (%) | Total rain (in) | Average daily maximum soil temperature (F) | Days between cover crop interseeding and corn harvest |
| 1 | Verona | 18 | 1.03 | 71 | 45 |
| 3 | Porter | 26 | 1.1 | 72 | 64 |
| 4 | Arlington | 30 | 2.11 | 65 | 57 |
| 8 | Marshfield | 32 | 3.04 | 63 | 70 |
Cover crop fall biomass and ground cover
Cover crops successfully established but as the season progressed growth, vigor, and stand diminished at all farms. Survival from summer stands was minimal for the V4 interseeded cereal rye at farms 2, 5, 6, 7, and 8 and the sparse growth prevented fall sampling at these locations.Farm 2 had a thick mat of cereal rye cover crop that was terminated in spring 2025 prior to interseeding, which likely prevented good seed to soil contact and could have reduced seed imbibition and germination and inhibited light interception by newly emerged seedlings. Other studies in the Midwest have shown that in conservation tillage systems with crop residue greater than 30% had poor cover crop stand density with aerial broadcast interseeding. Cereal rye interseeded at V4 corn and the late-interseeded cereal rye persisted until fall at farms 1, 3, and 4 (n=11). Annual ryegrass at farms 4 and 5 (n=5) and the multi-species mix at farm 8 (n=4) interseeded at the V4 corn growth stage persisted until fall. Cover crop fall sampling data from these farms were used in analyses.
Fall biomass (DM T/ac) did not exceed 0.5 DM T/ac for any cover crop treatment. The multi-species mix had the most biomass and greatest green cover by fall sampling. There was no advantage to interseeding cereal rye at V4 corn compared to waiting until mid-September. The late-interseeded cereal rye had 3-times more fall biomass compared to V4 interseeded cereal rye, despite half as many days between cover crop interseeding and corn harvest. Despite there being less total rainfall during the interseeding window for late-interseeded cereal rye, soil moisture was still relatively high which could have aided cereal rye germination during the late interseeding period. Annual ryegrass interseeded at V4 corn outperformed cereal rye, regardless of interseeding timing, in terms of fall biomass and ground cover. The cover crop species that were most successful by fall sampling were annual cover crops that will purportedly winterkill in Wisconsin, compared to overwintering cereal rye. Annual covers may be better suited for interseeding due to quick growth and being more shade tolerant compared to cereal rye.
Percent cover decreased from 30 DAI measurements to the fall measurements, which suggests decreased growth and emergence throughout the season. This could be due to corn shading preventing growth after establishment. Additionally, a really good crop of corn (>200 bu/ac) can out-compete the cover crop, resulting in poor to no cover crop stands after corn harvest. Decreased cover crop light interception may have occurred at these farms due to high corn yields. This could have been the issue with the farms that had no fall biomass to sample, as corn yields in this study averaged 203 bu/ac and were as high as 247 bu/ac.
Corn yield and forage value
Cover crops did not impact corn grain yield. Corn grain yield is lower in the multi-species cover crop strips (farm 8) compared to other plots that had data aggregated across multiple farms. Corn grain yield in the multi-species cover crop strips (159.75 bu/ac) were comparable to the Farm 8 average of 162 bu/ac. Notably, there was no difference between corn grain yield in the control plots compared to the V4 rye interseeding plots. This suggests that interseeding can be implemented without a yield penalty, although cover crop biomass in our study was low and this could have impacted our yield results. Developing recommendations for interseeding will require trials that have more consistent establishment from summer to fall to increase fall biomass and "test" the competition with corn. In our study, it is possible that corn actually outcompeted the cover crop since yields were high.
Forage quality analysis was conducted and then used with UW-Extension's hay market report to obtain the value of the fall biomass as a forage to determine if using CCs as an alternative forage has economic value that may compensate for increased costs incurred for establishment and maintenance or corn yield drag. Since we did not observe corn yield drag in this study, it is perhaps best thought of as an opportunity to recoup cover crop seed cost. Using the value of $20.57/acre seed cost for cereal rye and $16/acre seed cost for annual ryegrass reported from farmers that participate in the Wisconsin Cover Crop Data Network, only annual ryegrass had enough value as a forage to recoup the cost/acre of seed, which does not include the cost to establish (e.g., pay the drone operator). As one farmer put it, "there is high quality food out there, just not enough of it to justify fall harvest or grazing". Annual ryegrass interseeded at V4 corn has more potential as a fall forage compared to cereal rye interseeded at V4.
Table 5. Forage analysis results by cover crop treatment. Forage quality analysis was conducted and then used with UW-Extension's February 17, 2026 hay market report to obtain the value of the fall biomass as a forage. Value was calculated using the average price per ton ($120) for prime (RFQ >151) for large square bales. CP= Crude Protein, NDFD48=Neutral Detergent Fiber Digestibility at 48 hours, RFV=Relative Feed Value, RFQ=Relative Forage Quality, Ca=Calcium., P=Phosphorus, Mg=Magnesium, K=Potassium, S=Sulfur, Cl=Chloride
| Cover Crop Treatment | CP | Lignin | NDFD48 | RFV | RFQ | Milk/Ton | Ca | P | Mg | K | S | Cl | Value ($/acre) |
| V4 cereal rye | 22.04 | 1.51 | 78.40 | 131.45 | 162.49 | 2857.64 | 0.55 | 0.38 | 0.30 | 3.54 | 0.38 | 1.12 | 1.52 |
| V4 annual ryegrass | 20.28 | 1.59 | 79.70 | 160.79 | 224.67 | 3693.20 | 0.77 | 0.42 | 0.29 | 3.13 | 0.30 | 0.69 | 31.16 |
| Late-interseeded cereal rye | 23.81 | 1.51 | 78.23 | 145.36 | 176.48 | 3003.27 | 0.65 | 0.42 | 0.33 | 3.52 | 0.41 | 1.23 | 5.78 |
| V4 multi-species mix | 20.35 | 3.16 | 40.19 | 220.98 | 186.92 | 2872.75 | 1.52 | 0.33 | 0.40 | 3.18 | 0.30 | 0.66 | 42.60 |
Additional spring biomass and forage sampling will further clarify the economic value of these systems.
Educational & Outreach Activities
Participation summary:
Our team engaged in a range of education and outreach activities in support of the project, with particular emphasis on on‑farm demonstrations and peer-to-peer learning. In 2025, two field days were held at collaborating farms to showcase project objectives, discuss emerging data, and demonstrate drone-based interseeding technologies in real-world conditions.
The first field day was hosted in early June 2025 by Bill Powers and the Farmers of the Lemonweir Valley, a producer-led watershed group. Twenty-five farmers attended, along with county staff, community members, and their families. During the event, UW–Extension personnel presented baseline soil sampling results and discussed how those data compare to statewide soil health benchmarks. Powers shared his interest in drone interseeding and how it fits into his farm’s conservation goals. Heisler and Jones highlighted the broader value of producer-led watershed groups collaborating on research as a means to accelerate innovation and build shared learning networks. The event also featured a live drone interseeding demonstration in the project plots. Attendees had the opportunity to ask questions directly to the operator, observe the interseeding process in real time, and walk the plots after seeding. Printed handouts summarizing baseline soil sampling findings and contextualizing them with Wisconsin soil health benchmarks were distributed to every participant.
A second field day took place in September 2025, hosted by Pat Socha and the Eau Pleine Partnership for Integrated Conservation. More than 50 farmers and community members participated. As in June, UW–Extension and DATCP staff reviewed project objectives and baseline soil data. Attendees were then invited into the field to evaluate cover crop growth in the plots interseeded earlier in the summer and compare corn stands between interseeded and control treatments. This field day also included a live demonstration of drone interseeding into corn at leaf-drop—an opportunity driven by Socha’s interest in how timing influences interseeding success in grain corn. These repeated live demonstrations across the 2025 field days proved to be a critical educational approach, allowing farmers to observe, question, and experience this emerging application method firsthand. They also provided drone operators with valuable insight into the types of services and operational flexibility farmers need.
Beyond field days, project findings were also shared at the Wisconsin Water and Soil Health (WWASH) Conference in Wisconsin Dells on December 16, 2025. WWASH is Wisconsin’s premier statewide soil health conference and drew more than 300 attendees in 2025, historically with farmers comprising roughly half of participants. At the conference, Jones facilitated a roundtable session where he presented project results and engaged participants in discussions about the opportunities and challenges associated with interseeding cover crops. He distributed a detailed handout summarizing project findings, including data exploring how interseeded cover crops may support forage production. The session encouraged dialogue among farmers, conservation professionals, and agency staff and helped elevate awareness of drone interseeding as a developing tool for integrating cover crops in Wisconsin’s cropping systems.
Learning Outcomes
Project Outcomes
This project is contributing to agricultural sustainability by evaluating interseeded cover crops as a strategy to improve soil health, diversify forage resources, and maintain crop productivity in Wisconsin grain systems. Although the project is still in progress, preliminary results demonstrate promising economic, environmental, and social benefits for participating farmers and the broader agricultural community.
From an economic perspective, early findings suggest that interseeding cover crops into corn can be implemented without negatively impacting corn grain yield under certain conditions. Yield data reported thus far from cooperating farms indicate that interseeded cereal rye treatments performed similarly to the no-cover control in several locations where cover crops successfully established. These findings reduce adoption risk by demonstrating that, when successfully established, cover crop interseeding may be integrated into existing production systems without sacrificing cash crop profitability. Additionally, several interseeded cover crop treatments produced measurable biomass with high relative forage quality, indicating potential value as supplemental livestock feed. While fall biomass production was variable (and not able to be measured at some sites) and often limited for cereal rye, non-overwintering annual ryegrass and multi-species cover crop treatments generated greater forage biomass with high feed quality, highlighting opportunities for producers to offset cover crop establishment costs through forage utilization. However, there must be sufficient fall biomass production which was not always the case. Additional spring biomass and forage sampling will further clarify the economic value of these systems.
Environmentally, this project supports sustainability by promoting continuous living cover and reducing periods of fallow soil following corn grain harvest. Although fall establishment varied among sites due to environmental and management factors, half the locations demonstrated successful cover crop establishment through fall, which contributes to erosion reduction, improved nutrient retention, and enhanced soil biological activity. Spring soil health tests will be used to quantify these services. By evaluating multiple cover crop species and different establishment timings across diverse farm environments, the project is helping identify management strategies that improve establishment reliability. Planned spring 2026 sampling will provide further insight into soil health indicators such as microbial activity and aggregate stability, which are expected to respond positively to increased plant diversity and extended periods of soil cover.
Socially, this project is strengthening farmer-led research networks and supporting peer-to-peer learning across Wisconsin’s producer-led watershed groups. The coordinated multi-farm research approach allows farmers to evaluate conservation practices under real-world conditions while contributing to shared learning across watersheds. Farmer collaborators are actively engaged in research design, implementation, and evaluation, increasing the relevance and credibility of project findings. Outreach activities, including field days and educational materials, are facilitating knowledge transfer and assessing feasibility of interseeding systems. Even challenges encountered during the first year, such as variable establishment success, have provided valuable learning opportunities that inform adaptive management and future research priorities.
As the project continues, additional yield data, spring biomass measurements, forage quality analyses, and soil health assessments will provide a more comprehensive evaluation of sustainability outcomes. Additionally, knowledge gained from this project will be used to inform an update of the Midwest Cover Crop Council's cover crop selector tool for Wisconsin, specifically the addition of an early season interseeding goal. The collaborative framework developed through this project is expected to support long-term adoption of conservation cropping practices and strengthen partnerships between producer-led watershed groups, ultimately advancing the resilience and sustainability of Wisconsin agricultural systems.
A grain and livestock farmer from southern Wisconsin was impressed with the annual ryegrass interseeding performance and preferred that species over cereal rye, especially for fall grazing potential.
A farmer from south central Wisconsin connected with a farmer from northwest Wisconsin to discuss a method about interseeding while broadcasting urea, taking advantage of peer-to-peer learning opportunities and building experience.
Farmers were active in making observations in the plots during the growing season, and a couple of farmers noted that heavy rain after interseeding moved the seeds and stand establishment was less uniform and "clumpy" in many areas. These types of field-level observations are critical for success with new practices, and aren't necessarily captured in the data.