Undercover with Cover Crops

By: Dr. Jim Smart, Shelly Greving

One of the management practices gaining a lot of attention is the use of cover crops. Like many practices that receive a lot of publicity, there are clear advantages to using them. However, those advantages quickly diminish when they are not managed properly. Cover crops are high atop the current list of trends, but diligent management is essential if you want to capture the benefits and avoid potential headaches.

Soil Fertility

Actively growing plants, which cover soil most of the year, help to maintain or improve soil microbial populations, essentially keeping the soil alive all year. This improves the status of living organisms in the soil and especially increases earthworm populations.

Soil Quality

Following the termination of cover crops, residue breakdown provides a slow release of nutrients that
become available during the cash crop’s growing season.

The residue acts as mulch on the soil surface which allows it to retain moisture, reduce the temperature
of the soil surface, and provide an environment for increased root growth.

During the 2014 National Dealer Seminar Cover Crop Panel, Ag Spectrum associate, Kathleen Holthaus, shared that cover crops additionally help to reduce soil compaction with their strong rooting system. The resulting cavity leaves effective root channels for the next crop.

Weed Management

Cover crops increase the degradation of weed seed on the soil surface, enhance stalk degradation of the prior crop, and suppress weeds. Thick cover crop stands compete well with weeds during their growth period and can prevent most germinated seeds from reproducing. In addition, terminated cover crops may create a thick layer on the soil surface that can be nearly impossible for the weeds to penetrate.

Cover crops have also been used successfully in groves and orchards and when grown between tree rows, the cover crops effectively suppress weed growth.

Water Management

Cover crops reduce erosion and subsequent nutrient and pesticide loads on streams, waterways and lakes. Sedimentation loss from fields contaminates these bodies of water and reduces the nutrient content of the remaining soil. This also impacts the availability of nutrients such as phosphorous, potassium, and nitrogen. 

Retention of these nutrients make them less likely to leach or run-off into lakes or streams and in turn, the cover crop retains the nutrients as it decomposes and becomes available to the cash crop. Remember, GroZyme aids in the decomposition of organic residue, making the nutrients more readily available to the future crop.

Management and Costs

Planting time and management costs can be challenging. Be aware that planting cover crops too late usually leads to less growth, reduced soil cover, and decreased soil benefits. Likewise, late termination of cover crops can lead to spring planting delays, excessive soil moisture, and decreased stands. 

Seed cost and availability are two other challenges growers often face. Planning well in advance and being flexible when selecting the cover crop varieties are two ways to overcome cost and availability barriers.

Potential to Become a Weed

Some species of cover crops have delayed germination due to a hard seed coat not being stratified. Hairy vetch may continue to germinate throughout the summer and become a difficult weed to control in the cash crop planted. Some genotypes of annual ryegrass can be resistant to the herbicide glyphosate and thus could become a problematic weed if not managed properly.

Decrease in Available Soil Moisture

Early spring cover crops may utilize too much moisture, creating a drying effect on the soil.  If ryegrass or cereal rye is not terminated prior to stem joint formation they can provide mulch for the soil, keeping it wetter than normal. This is beneficial during a hot, dry summer, but creates challenges during planting or seeding if the soil remains too wet and enhances soil pathogen growth. 

Proper Termination

Timely termination ahead of spring planting can also be a challenge. Lynn Yost shared that in 2013, they planted several acres of cover crops in southwestern Ohio. However, they lost at least 15-bushel of beans per acre on one farm because it was too wet to get into the fields to terminate. The crop kept growing until it was shoulder high in some places and the soybeans didn’t get planted until the middle of June.

Dr. Darrell Norton, Professor Emeritus in Agronomy and Biological Engineering at Purdue University and former director and researcher at the USDA-ARS Soil Erosion Research Laboratory in West Lafayette, Indiana warned that although cover crops with deep-rooted systems are great at penetrating compaction layers and capturing nitrogen, the plant must still decompose before that nitrogen is available for the cash crop in the spring. He suggests terminating the cover crop at least two weeks prior to planting the cash crop.

Insurance and Aid Eligibility

Farmers should also be aware that raising cover crops could impact their eligibility for crop insurance programs and government aid. To be sure your payments are not affected, consult your local Farm Service Agent before planting.

Achieving Success

To achieve maximum results by using cover crops, it is important to determine the producer’s goals and expectations prior to initiating cover crop usage.

Bill Barga, Ag Spectrum associate in western Ohio, offers that success can be achieved by planting cover crops early in the growing season and terminating properly. With an increased awareness of the difficulties that may occur, proper planning and management techniques, and flexibility, cover crop challenges can be minimized.


When implemented properly, the benefits of planting cover crops are numerous. Based upon the 2012-2013 Cover Crop Survey conducted by CTIC and SARE, these are the primary benefits farmers gain from implementing cover crops.

  • Reduces Soil Compaction
  • Reduces Soil Erosion
  • Scavenges Nitrogen
  • Weed Management
  • Increases Yields for Future Crop
  • Nitrogen Source
  • Fibrous Rooting System
  • Deep Tap Roots
  • Economic Return
  • Decreases Future
    Production Costs
  • Winter Kills Easily
  • Winter Hardiness
  • Reduces Disease
  • Insect Control
  • Wildlife Benefits
  • Enhance Soil Drainage
  • Breaks Down Crop Residue
  • Increases Organic Matter Through Increased Root Production
  • Nematode Control


While the benefits of using cover crops are vast, growers should also consider the difficulties. Based upon the 2012-2013 Cover Crop Survey conducted by the Conservation Technology Information Center (CTIC) and North Central Sustainable Agriculture Research and Education (SARE), these are the primary cover crop challenges farmers experience.

  • Establishment
  • Time/Labor Requirements
    and Increased Management
  • Species Selection
  • Cover Crop Seed Cost
  • Planting/Management Costs
  • Cover Crop Uses Too Much Soil Moisture
  • Availability of Cover Crop Seed
  • Cover Crop Becomes a Weed
  • No Measurable Economic Returns
  • Increased Insect Potential
  • Increases Overall Production Risk
  • Yield Reduction in Following Crop
  • Nitrogen Immobilization
  • Increased Disease Potential

Additional results from the 2012-13 Cover Crop Survey conducted by
CTIC and SARE can be found at