Evaluating "Flex Ear" Corn Varieties for Agronomic and Conservation Performance

Progress report for ONE20-379

Project Type: Partnership
Funds awarded in 2020: $29,363.00
Projected End Date: 12/31/2022
Grant Recipient: University of Vermont Extension
Region: Northeast
State: Vermont
Project Leader:
Jeffrey Sanders
University of Vermont Extension
Dr. Heather Darby
University of Vermont Extension
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Project Information


Although widely adopted, barriers remain to establishing a successful interseeded cover crop. Cover crop growth can be inhibited by the inability of light to penetrate the corn canopy cover which impedes cover crop photosynthesis. Shade from the corn canopy can be reduced with lower corn populations or leaf architecture that is more vertical. Understandably, farmers are reluctant to decrease corn populations in order to promote cover crop growth out of concern about decreasing crop yield. Flex ear or indeterminate hybrids may be able to offset yield decline with higher quality while also promoting cover crop growth with more vertical leaf architecture.

The project proposed here will provide information in identified research gaps on varietal differences in “flex” or indeterminate corn hybrids, and the impact of corn populations on both corn yield and cover crop success. In on-farm research conducted over two years using rigorous scientific methods, six corn varieties will be evaluated for yield and quality at seeding rates of 26K, 30K, and 34K. Cover crop success of interseeded cover crops will be determined by cover crop biomass after cash crop harvest. Light infiltration will be measured bi-weekly using LI-COR Sensor to determine if there is a relationship between cash crop shade and cover crop growth.  Research results of data analyzed with robust statistical methods will be presented in a technical report, factsheet, webinar, and at field days, workshops, and conferences. Over 500 stakeholders will be reached through materials presented online, in print, and in-person.

Project Objectives:

Broad Objective. This project seeks to support farmers in building sustainable cropping systems while maintaining yields and economic viability.

Objective 1. Identify corn varieties and seeding rates that meet cash crop yield and cover crop biomass goals.

Objective 2. To identify indeterminate corn varieties suitable for Northeast production.

Objective 3. Determine the profitability of the cropping system, calculating the cost of corn seed, cover crop seed, corn yield, cover crop termination (if applicable), and purchased feed (to offset lost corn yield). This information can be used to choose varieties that meet the farmer’s conservation and profitability goals.

Objective 4. Create outreach with farmer-friendly technical reports, factsheets, webinars, and via presentations at field days and the Northeast Cover Crop Council Conference. Over 200 farmers, agribusiness personnel, technical service providers, and other stakeholders will be reached.




Over the years, corn cropping systems have primarily prioritized yields over ideal land stewardship practices. Climate change challenges this system in the Northeast because of the increase in high-intensity rainfalls resulting in an increase in crop failures, soil loss, and nutrient runoff. Implementing conservation practices like cover cropping can build soil health, retain crop nutrients, protect water quality, and stabilize crop yields. Interseeding cover crops is a common way to lengthen the window of opportunity for growth especially in areas with short growing seasons. Although widely adopted, barriers within the corn production system have minimized the successful establishment of interseeded cover crops.

In an attempt to maximize yields, silage corn is planted at denser populations which reduces the amount of sunlight reaching the soil, inhibiting cover crop growth. Corn varieties that perform best at high seeding rates are those promoted by seed companies. As a result, determinate hybrids are the most common type purchased and planted on the landscape. Determinate hybrids have corn ears with a determined maximum size. In contrast, indeterminate or “flex” ear hybrids are not widely advertised or known about by the farming community.  Flex hybrids can grow to a larger ear size depending on environmental conditions. As an example if the corn population is reduced a flex hybrid will compensate by increasing ear size whereas the non-flex types will keep the same ear size. Flex hybrids also tend to have an upright leaf architecture.  Hence the integration of flex hybrids onto farms may help promote the growth of interseeded cover crops , but research is needed.

This project will provide agronomic knowledge to farmers regarding selecting corn hybrids and cultural practices that best balance obtaining viable yields with the conservation benefits of cover cropping. On-farm research trials will be conducted that examine the attributes of indeterminate ear corn silage varieties by quantifying the impact of corn variety and seeding rates both on cash crop yield, cash crop quality, and cover crop biomass. In addition, the profitability of corn varieties in systems that utilize conservation practices will be calculated by estimating reductions in purchased energy sources, and the offset of yield reductions through increased quality. This will result in innovative data on conservation and profitability in corn cropping systems, and educational and outreach materials. A database, factsheet, and technical report will be developed. This information will be available online and in print at field days, workshops, and conferences.

While this question has not been extensively studied, Northwest Crop and Soils have implemented similar on-farm partnerships in corn cover cropping systems. These past successful studies, outreach, and farmer partnerships will inform the project. The innovative research and outreach materials generated by this project will support farmers in building more sustainable farming systems by providing information that helps farmers reach yield, conservation, and viability goals.



Click linked name(s) to expand
  • Tom Machia - Producer
  • Roger Rainville - Producer


Materials and methods:

2020 Update Report:

We have selected the hybrids for the project (see below) and have reviewed the projects implementation plan.  We are in the process of acquiring the actual seed and laying out the plots on paper.  The work of this project will not start on the ground until mid-May 2021.  We are also currently reviewing interseeding other interseeding projects around the country to see it we can utilize any new information in our strategy.  


Objective 1. Conduct research trials to identify corn varieties and seeding rates that meet cash crop yield and cover crop biomass goals.

  1. Trial location and research design.

Collaborating farmers willing to conduct the trials have already been identified. Roger Rainville will host the trial at Borderview Research Farm in Alburgh and Tom Machia will host the trial in one of the most impaired watersheds in the Lake Champlain Basin. Treatments will include six different corn varieties (3 determinate and 3 indeterminate varieties) seeded at 26,000 28,000, 30,000, 32,000, 34,000, and 36,000 plants per acre. The main plots will be seeding rates and subplots will be variety. Agronomic methods will be those commonly used in corn silage systems in the local region. Corn silage varieties will be in the same relative maturity range. This project will utilize the following corn varieties: Determinant (fixed ear) Pioneer P9492, Brevant B95V86AM, and Brevant 97V84AM.  Indeterminant (Flex) ears will include Pioneer P9608, Brevant B97F86AMXT, DeKalb DKC 44-80RIB.    Corn will be interseeded with a cover crop mix at the V4 to V6 leaf stage, at both locations. The cover crop mix will be planted at a rate of 26.5 lbs/acre and consist of annual ryegrass (20 lbs/acre), red clover (5 lbs/acre), and tillage radish (1.5 lbs/acre).

  1. Data collection.

Light infiltration data between cornrows will be taken every other week from corn emergence until harvest with a LI-COR LI-191R Line Quantum Sensor. At emergence, corn populations will be assessed by counting 17.5” in three rows in each plot. Corn plots will be harvested with a tractor and two-row chopper. Yields will be weighed with portable platform scale. A subsample of approximately one pound will be taken from each plot to determine dry matter and forage quality.  A 10 plant subsample of corn will be taken from each plot to determine ear and stalk weights. Cover crop biomass will be sampled by clipping biomass from a total of 3 quadrats (1.5 x 1.5ft) per plot. The clipped biomass will be sorted by species and weighed to determine inter cover crop competition, and weed biomass. To process corn silage samples for analysis, they will be ground with a Wiley mill, then ground with a cyclone sample mill (1mm screen) from the UDY Corporation at UVM’s Cereal Testing Lab. Quality will be determined with FOSS NIRS (near-infrared reflectance spectroscopy) DS2500 Feed and Forage analyzer. Quality metrics will include crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF), 30-hour digestible NDF (NDFD), total digestible nutrients (TDN), and Net Energy-Lactation (NEL).

  1. Data analysis.

The general linear model analysis will be calculated using the general linear model procedure of SAS (SAS Institute, 2008). All treatment factors in this experiment will be considered fixed with the exception of replicates. Mean separation among treatments involving variety and seeding rates will be obtained using the Least Significant Difference procedure when significant F-tests (P<0.10) are observed.


Objective 2. To identify indeterminate corn varieties suitable for Northeast production.

Dr. Heather Darby works closely with University of Maine, Cornell University, and Penn State University to develop and host corn variety evaluation trials. The trials are held annually in conjunction with seed companies, nutrition companies, and farmers. Each year there are over 200 corn hybrids evaluated for yield and quality across the region.  An analysis of these yearly results will be conducted to search for indeterminate (flex ear) corn hybrids that also rank high for yield and quality. The analysis will be composed into a quick reference table that allows farmers to easily search for varieties that meet their agronomic goals and also have indeterminate characteristics.  It will be housed on UVM’s Northwest Crops and Soils Program website and shared with collaborating programs.

Objective 3. Determine the profitability of the cropping system.

From the farmer's perspective, it will be important to determine whether the use of these hybrids in their cropping systems will be profitable.  This proposal will use the Ohio State University's Enterprise budget tool which generates a corn silage production budget to calculate the profitability of each of the hybrids used in this project.  The tool can be located at https://ag.purdue.edu/commercialag/home/resource/2018/05/corn-silage-production-budget/.   The tool will utilize inputs including but not limited to; the cost of cash crop seed, fixed costs for cover crop seed and field operations (labor, equipment, and fuel costs for field preparation, planting corn, planting a cover crop, fertility applications (fertilizer and/or manure), weed control (tillage or chemical), and harvest costs.  The output from this worksheet will provide a clear way to evaluate how these hybrids perform on the trial farms.  UVM Extension staff will work with the farmers to complete the spreadsheets and then share the data with stakeholders.  

Objective 4. Provide educational resources.

Results will be published in farmer-friendly technical reports, factsheets, webinars, and presentations at field days and the Northeast Cover Crop Council Conference. Over 400 farmers, agribusiness personnel, technical service providers, and other stakeholders will be reached each year of the grant.  See the Outreach section for more detail.


Participation Summary

Education & Outreach Activities and Participation Summary

Participation Summary:

Education/outreach description:

The NWCS Program has a well-established and extensive outreach program. Technical reports dating back to 2012 are available on the Program’s website.  The Annual Field day draws over 225 attendees. The Program’s YouTube channel has over 300 videos with 2400 subscribers and 937,915 views. NWCS has several webinar series that focuses on tile drainage, cover crops, and no-till. Other educational efforts the NWCS has engaged in include courses for Custom Manure Applicator Certification, Required Agricultural Practices for Small Farm Operations, and an Agricultural and Water Quality Curriculum for high school technical centers. Hence the project team has vast experience and networks to distribute the project information locally, regionally, and  nationally.

The information developed through on-farm research will be delivered to farmers and other stakeholders through a diverse mix-media outreach program. The outreach materials that will be developed include:

1. a technical report that documents research results in a farmer friendly format;

2. a factsheet focused on corn variety selection and profitability analysis for successful cover crops;

3. a quick reference table that highlights the yield and quality of indeterminate corn hybrids available in the Northeast;

3. a 3 part webinar series focused on modifying corn practices (including variety, herbicide management, and population) for cover crop success.

In addition to outreach materials a field day will be held at the Machia farm to highlight project results and other cover crop and corn strategies for the northeast. The field day will be held in the fall of 2022. The UVM Crop and Soil Annual Field Day (held at Borderview Farm in late July) will also highlight the project results and allow farmers to observe corn and cover crop strategies. Lastly, the project results will be delivered at the UVM No-Till & Cover Crop Symposium held in Burlington each February. We expect that over 400 stakeholders will be reached through these events.

As applicable, materials will be posted on the Northwest Crops and Soils Program website (https://www.uvm.edu/extension/nwcrops), available at events (field days, conferences, workshops, etc.), advertised on social media pages, and uploaded to the Program’s YouTube channel (https://www.youtube.com/user/cropsoilsvteam/)


Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.