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Principles for Transitioning to Organic Farming:�Cover Crops

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Authors

Adria Fernandez, Claire Flavin, Kristine Moncada, Constance Carlson and Craig Sheaffer

Updated 2026 (originally published 2017)

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What is a cover crop?

“Crops including grasses, legumes and�forbs for seasonal cover and other conservation�purposes.”

Natural Resources Conservation Service

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Cover crop definition

Typically planted after cash crop harvest
May also be used in fallow years
Reduces time when soil is bare
Also called plowdown or green manure
Plant material is incorporated

Over-wintered rye

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Cover crops on organic farms

Not required for organic, but valued in rotations
Contribute to biological approach to pest, weed and disease management

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Cover crops in organic systems

Reduce erosion from wind and water
Increase soil organic matter content
Capture and recycle or redistribute nutrients in the soil
Promote biological nitrogen fixation
Suppress weeds
Retains soil moisture
Minimize and reduce soil compaction

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Cover crops overview

Benefits
Cover crop options
Meeting your goals
Establishment and termination
Rotations
Economics

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Benefits of cover cropping

Soil health
Improved water quality
Weed control
Pest and disease control
Enhanced nutrient cycling

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Farmers’ thoughts on the biggest benefits

Top 3 results when farmers were asked to “Name the single biggest benefit you receive from cover crops…” in the SARE Cover Crop Survey in 2015-16

Improves soil health
Erosion control
Increases organic matter

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Increased soil organic matter

Incorporating cover crops adds biomass
Biomass is processed by microbes into soil organic matter

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Compacted soil without cover crop

Roots have trouble penetrating
Soils can’t absorb water easily
Can lead to more runoff, erosion and less subsoil moisture

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Soil with cover crop

Reduces compactions
Creates paths for water to infiltrate

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Improved water quality

Reduced sediment runoff
Retention of nutrients on farm
Catch crops – hold nitrogen and phosphorus to prevent pollution

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Improved nutrient cycling

Capture of excess nutrients
Biological nitrogen fixation by legumes
Biomass decomposition increases microbial activity leading to faster crop residue breakdown

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Improved weed control

Compete with weeds
Allelopathy – chemicals that suppress weeds

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Reduced pests and disease

A honeybee pollinating a cover crop

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Cover crop risks

Increased management, labor and seed costs
Depletion of soil moisture or nutrients
Interference with cash crop establishment

Hairy vetch cover overgrowing corn crop

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Cover crop species

Winter rye and hairy vetch mix

Narration: To make cover cropping work for you, you will need to choose cover crops and practices that can benefit your main crops while minimizing the potential risks. An enormous range of plant species can potentially be used as cover crops. However, in practice, there are only a handful that most farmers find practical for use in the Upper Midwest. To maximize benefit and minimize risk, you’ll want to start by thinking about what purpose you want the cover crop to serve and where you want it to fit in your rotation. This allows you to consider the set of crops suitable for a given purpose, and select one with a growth period that fits your cropping schedule. <In this picture, we show winter rye and hairy vetch plants growing together in a cover crop mix.>

Image: Craig Sheaffer, University of Minnesota

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Cover crop characteristics

Legume, grass or broadleaf
Overwintering vs. winter-killed

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Cover crops for northern environments

Constraints – short growing seasons, harsh winter conditions
Common cover crops: winter rye, annual ryegrass, spring oats, hairy vetch, red clover, brassicas

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Winter rye

Cool-season annual grass
Very winter-hardy
Suppresses weeds
Can be used for spring grazing or harvested for grain
High water use

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Annual ryegrass

Quick to establish, even at cool temperatures
Winter-kills; no need to terminate
Provides winter soil protection and spring water infiltration
Moderate water use

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Spring oat

Quick-growing in fall
Winter-kills
Moderate water use
Inexpensive, low risk
Can be seeded into standing soybean

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Hairy vetch

Strong nitrogen fixer
Overwinters, though somewhat unreliably
Low-medium water use

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Red clover

Short-lived perennial legume
Often grown as forage, but can be used as cover crop
Can be underseeded with small grains
Good winter-hardiness
Nitrogen source

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Brassicas

Mustards, turnips, rapeseed/canola, radishes
Rapid fall growth, then winter-kill
Tender biomass degrades quickly
Sometimes used as biofumigants

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Cover crop mixtures

Common two-species mixtures are hairy vetch/winter rye and peas/oats
May be difficult to get all components to establish

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Consider goals in selecting cover crops

Provide nitrogen
Scavenge nitrogen
Build soil organic matter
Control erosion
Improve soil structure
Suppress weeds
Control disease
Provide for beneficial insects

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Nitrogen fixers and scavengers

Legumes fix nitrogen
Should be planted with appropriate Rhizobium inoculant
Grasses and broadleaves can scavenge nitrogen

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Nitrogen (N) credits from cover crops

Alfalfa – 40 to 100 pounds of nitrogen per acre
Red clover – 40 to 80 pounds of nitrogen per acre
Hairy vetch – 40 to 90 pounds of nitrogen per acre
Source: Laboski & Peters, 2012

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Building soil organic matter

High biomass crops
Winter-hardy to enable spring growth
Recalcitrant (slow to degrade) materials

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Erosion control

Crops with dense root systems
Thick, fast-growing stands

Eroded topsoil

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Improved soil structure

Strong, deep-penetrating crop roots
Brassicas such as tillage or oilseed radishes

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Weed control

Smother crop to exclude weeds
Allelopathy – release of chemicals to suppress weeds
Hairy vetch, winter rye, oats, annual ryegrass and brassicas can help control weeds

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Disease control

Interrupt pathogen growth environment by planting non-host species
Choose cover crops from different families
Brassicas may have limited suppressive effect on fungal pathogens

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Habitat and food for beneficial insects

Flowering crops feed pollinators and attract predatory insects

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Midwest Cover Crop Selection Tool

m idwestcovercrops.org/selector-tools/

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Seed sourcing

Available from commercial seed suppliers
Varieties may not be specified
Choose local sources for winter-hardiness

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Establishing cover crops

Winter rye – mid-July to early October
Annual ryegrass and spring oat – mid-August
Hairy vetch and red clover – early August
Brassicas – August

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Planting methods

Drilling
Broadcasting, with or without incorporation
Aerial or overhead seeding; generally better for smaller-seeded crops

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Typical planting methods

When farmers were asked their typical cover crop seeding method in the SARE Cover Crop Survey in 2022-2023, the percent responses were:

44.1% Drill
31.8% Broadcast by ground
12.7% Broadcast by air (aerial)
11.4% Row crop planter or other

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Methods matter!

Broadcast

Broadcast and incorporate

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Seeding rates in pounds/acre

Species	Broadcast	Drilled
Winter rye	90-160	60-120
Annual ryegrass	20-30	10-20
Spring oat	100-140	80-110
Hairy vetch	25-40	15-20
Red clover	10-12	8-10
Brassicas	8-30	5-13

From Managing Cover Crops Profitably, SARE, 2007

Narration: You should check with your seed supplier for recommended planting rates, but in general, higher rates will be needed if you are broadcasting seed onto the soil surface versus drilling or incorporating the seed. <In this table of cover crop seeding rates, the winter rye broadcast seeding rate is 90 to 160 pounds per acre and 60 to 120 for drilling. The annual ryegrass broadcast seeding rate is 20 to 30 pounds per acre and 10 to 20 for drilling. The spring oat broadcast seeding rate is 100 to 140 pounds per acre and 80 to 110 for drilling. The hairy vetch broadcast seeding rate is 25 to 40 pounds per acre and 15 to 20 for drilling. The red clover broadcast seeding rate is 10 to 12 pounds per acre and 8 to 10 for drilling. The brassica broadcast seeding rate is 8 to 30 pounds per acre and 5 to 13 for drilling. This data is from Sare's Managing Cover Crops Profitably publication in 2007.>

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Terminating cover crops

Achieve full kill
Prevent damage from allelopathy and planting interference by residues to the following crop

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Preferred termination methods

From a NRCS survey in 2014, percent of respondents and their preferred cover crop termination:

49% Tillage
20% Winter kill
19% Mow
12% Other

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Termination method and regrowth risk

Implement used	Incorporation?	Risk of regrowth
Moldboard plow	Yes	Low
Chisel plow	Yes	Moderate
Disking	No	Moderate
Flail chop	No	Moderate
Rotary mow	No	High
Roll and crimp	No	High

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Establishing the following crop

Terminate cover crops before desired planting date

1 week if incorporated
10 days if surface residue

Some crops (e.g. soybean) tolerate fresh cover crop residue well

Soybean in winter rye residue

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Cover crops in organic no-till

Must be terminated at correct stage
Can delay soil warming
Can make surviving weeds difficult to manage

Narration: In recent years, there has been quite a bit of research toward the development of organic no-till methods, in which heavy cover crop stands, generally rye and/or vetch, are killed by mowing or roller-crimping and left in place to serve as a weed-suppressing mulch, into which the following crop is directly planted. These techniques have proved successful in some regions but can be challenging in northern environments with short growing seasons. Cover crops must be terminated at the right maturity stage to prevent regrowth, which is sometimes too late to allow timely cash crop planting. A thick layer of mulch can also delay soil warming, and weeds that succeed in penetrating the mulch layer can be very difficult to manage. However, many farmers have expressed interest in the prospect of cover-crop-based organic no-till, and research is ongoing. <This image shows a rye cover crop with high biomass in the process of being roller-crimped and producing a very thick mulch on the field soil surface.>

Image: University of Minnesota

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Corn-soybean with rye cover

Year 1: Corn with rye
Year 2: Soybean
Good option during transition

Narration: Finding ways to fit cover crops into your rotation is a little like putting together a jigsaw puzzle. We’ll look a little bit at how cover crops can be used to diversify corn-and-soy-based rotations. One of the most common cover cropping practices in corn-soy systems is planting rye after the corn crop. Winter rye seed can be drilled into corn stubble, or is sometimes broadcast into a standing corn crop to allow the rye to establish before corn harvest. <This image shows rows of young rye seedlings growing between rows of corn plants.> The rye is then terminated in the spring before soybean planting. This can be helpful as the rye will suppress early-emerging weeds before soybean planting, and soybeans are very tolerant of cereal rye residue, so their establishment should not be adversely affected. A corn-rye-soy rotation can be a good foundation for a farmer transitioning to organic.

Image: Reagan Noland

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Corn-soybean-small grain with rye and vetch covers

Year 1: Corn with rye
Year 2: Soybean
Year 3: Small grain-hairy vetch
Legume provides nitrogen (N) for subsequent corn crop

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Corn-soybean-small grain with underseeded clover

Year 1: Corn
Year 2: Soybean
Year 3: Small grain underseeded with red clover
Used successfully by many organic farmers

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Quote from a farmer…

“ We raise short-season crops. For us, that has meant raising organic dry edible beans, sweet corn, or peas. It allows us to raise more cover crops that get closer to full biomass production before termination.”

– Jon Luhman, MN

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Cover crop profitability

From SARE Cover Crop Survey in 2015-2016, percent of respondents and their experience with cover crop profitability:

34.5% “Not enough data or experience to tell”
33.7% “Cover crops increase profitability”
26.1% “Cover crops do not affect profitability”
5.7% “Cover crops decrease profitability”

Narration: With cover cropping, like with any new practice, you’ll want to assess how it will affect your farm’s bottom line before you get started. <A survey was conducted in 2015 to 2016 by SARE that included a question on cover crop profitability.> Of the cover crop-using farmers surveyed by SARE, about a third said that cover crops increased their overall profitability, while less than 6% reported a decrease in profitability. The rest reported that cover crops did not affect profitability, or they did not have enough data or experience to tell. <The exact percentages for each response found in the survey were 34.5% for “Not enough data or experience to tell”, 33.7% for “Cover crops increase profitability”, 26.1% for “Cover crops do not affect profitability”, and 5.7% for “Cover crops decrease profitability”.> The effects of cover crops on your farm’s profitability will depend on the balance of costs and returns that you obtain from cover cropping.

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Cover crop costs

For both planting and termination
Seed cost
Equipment
Fuel
Labor and/or custom work

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Cover crop returns

Yield benefit (rotation effect)
Nitrogen credit
Soil protection
Government incentives

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Cropping Systems Calculator

Land Stewardship Project
Excel tool to calculate costs
Available at landstewardshipproject.org

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Conclusions

Clarify your goals or objectives
Identify the best time and place for a cover crop in your system
Choose well-established practices
Experiment on small acreage
Investigate funding opportunities

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Cover crop funding opportunities

Environmental Quality Incentives Program (EQIP)
Conservation Stewardship Program (CSP)
Contact your local Extension or NRCS office for currently available opportunities

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Acknowledgement – Organic Transitions Program

This project is supported by the U.S. Department of Agriculture, National Institute of Food and Agriculture, Organic Transitions Program under award number 2013-51106-21005.

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Acknowledgement – TOPP

This project is supported by the U.S. Department of Agriculture, Agricultural Marketing Service, National Organic Program under the Transition to Organic Partnership Program (TOPP) in the Midwest region.

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Disclaimer

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and should not be construed to represent any official USDA or U.S. Government determination or policy.

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Equal opportunity statement

The University of Minnesota shall provide equal access to and opportunity in its programs, facilities, and employment without regard to race, color, creed, religion, national origin, gender, age, marital status, familial status, disability, public assistance status, membership or activity in a local commission created for the purpose of dealing with discrimination, veteran status, sexual orientation, gender identity, or gender expression.

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For more information

Please see organicag.umn.edu for more information about this project.