Digging In

Cover Crops: Which one should I choose?

Cover Crops: Which one should I choose?

By Lisa Kubik on Thursday, 12 September, 2019

As harvest approaches, we also think about seeding cover crops, if we have not already. What type of cover crop seed you should use depends on your goals.  If your goal is to graze cattle on the cover to extend your grazing days, the seed you choose will be different than if you want to increase the weed control in next year’s crop.  Some cover crops are great at taking up excess nutrients that may be found in the field and others are great at breaking up heavily compacted areas of a field. These goals, as well as other factors, will help to determine the best species, or species mix, to use on your farm.

When choosing the variety of cover crops to plant, there are many ways to get started.  Whether you want your cover crop to live through the winter, kill after a frost, or grow the most biomass in the summer are several ways to look at it. This is determined by your ideal planting time and goals for the crop.

Winter Hardy- These cover crops are generally established in the fall, will live through the winter and add more growth in the spring. Winter hardy crops have to be terminated before planting the next cash crop in the spring. Some of these species are cereal rye, wheat, triticale, barley, and hairy vetch.

  • Cereal Rye 
    • Most widely-used cover crop in the Midwest
    • Soil health benefits: breaks up compaction layers, erosion control, fast biomass growth, grazing and forage potential, nutrient scavenger
    • Caution using before corn, due to high carbon to nitrogen ratios and potential allelopathic effects. Early termination and starter with plenty of nitrogen applied upfront help to minimize nitrogen tie-up. Plant 2 inches deep with a well-closed seed trench to avoid allelopathy.
    • Allowing more spring growth could improve weed control in soybeans
  • Wheat
    • Good option similar to cereal rye, better forage option
    • Slower spring growth and less overall biomass than cereal rye.
    • Soil health benefits: breaks up compaction layers, erosion control, fast biomass growth, grazing and forage potential, nutrient scavenger
  • Triticale
    • A cross between cereal rye and wheat
    • Soil health benefits: breaks up compaction layers, erosion control, fast biomass growth, grazing and forage potential, nutrient scavenger
    • Not as hardy as cereal rye, but generally better than wheat.
    • Mixes well with other species
    • Spring and winter varieties available
  • Barley
    • Simple to grow cover that is commonly used in a mix with other species
    • Soil health benefits: controls erosion, lots of biomass, suppresses weeds
    • Less winter hardy than cereal rye or wheat
    • Less concern in front of corn crop
  • Hairy Vetch
    • Mix with cereal rye for increased weed suppression and increased winter survival of hairy vetch
    • Soil health benefits: source of nitrogen, increases weed control
    • Slow-growing cover crop so seed early for best growth
    • Not a good option for grazing.
    • Terminate before seed production to avoid hard seed

Conditional Winter Hardy- The ability of these covers to overwinter is primarily determined by planting date. Late summer/early fall planting ensures that the plants are able to get well-established before a killing frost.  With that early establishment, these covers are more likely to survive the cold temperatures and continue growing in the spring. In the case of a late establishment or difficult winter, have the potential to lose much of the stand established. Some of these species include annual ryegrass, rapeseed, clovers, most legumes.

  • Annual Ryegrass
    • Produces large amounts of below ground biomass with less above ground growth than cereal rye 
    • Soil health benefits: reduces erosion, surface compaction and scavenges for nutrients
    • Adding oats to the mix could help protect the ryegrass and help it to overwinter
    • Can be difficult to terminate in the spring so timely and proper herbicide applications are needed
    • Thrives in shaded conditions, so good option for interseeding
    • Avoid Italian ryegrass- generally used for forages and are mixed varieties
  • Rapeseed
    • Most found in a cover crop mix
    • Soil health benefits: scavenges for nutrients, reduces some soil-borne pathogens
    • Most-likely will winter kill but is not controlled with glyphosate if it doesn’t
  • Crimson Clover
    • Winter annual that also attracts pollinators and beneficial insects
    • Soil health benefits: great source of nitrogen, builds soil structure, weed suppression
    • Option for livestock grazing or forage
    • Does well mixed with cereal rye or other cover crops
  • White Clover
    • Shortest growing type of clover that tolerates traffic and compaction
    • Soil health benefits: breaks up compaction, moderate nitrogen fixer
    • Does well interseeded, frost seeded, or in a cover crop mix

There are many other types of clover including berseem, alsike, sweet, red, balansa, etc. Each type of clover has different traits and benefits, so make sure you do your research before planting

Winter Kill- These cover crops terminate due to cold temperatures. Many require temperatures in the lower twenties to high teens for termination. Occasionally with a good cover of snow, they will have the potential to overwinter though. Some of the most common winter kill species include oats, turnips, and radishes.

  • Oats
    • Quick-establishing cover for spring or fall
    • Soil health benefits: good erosion control
    • Mix well with other covers as a nurse crop
    • Option to add biomass for grazing mixes
  • Turnips
    • Good option for breaking up compaction
    • Soil health benefits: scavenger for nutrients, suppress weeds, breaks up compaction
    • Not as vigorous in growth as radish, but superior option for grazing, but should not comprise more than 35% of the livestock diet
    • Performs well in a mix with other covers
  • Radishes
    • Rapid growth and a deep tap root
    • Soil health benefits: breaks up compaction, take up nutrients, suppress weeds
    • Best results when planted in a mix late summer/early fall
    • Do not let go to seed
    • After freeze rotting radishes create a strong odor so be cautious in residential areas

Summer Annual- The cover crops in this category are heat-driven and typically are planted early-mid summer.  They cannot handle a frost or freeze, so should not be planted in the fall. These are many times planted as a mix and used for grazing, harvested forage, reducing extreme compaction in areas or preventive planting acres.  Common summer annuals include sorghum, sudangrass, sorghum-sudan, buckwheat, millet, and sun hemp.

  • Sorghum-sudan
    • Extremely fast-growing, good source of forages
    • Soil health benefits: erosion control, nutrient scavenger, builds topsoil, prevents weeds
    • Caution grazing during and after a frost and before plants are 18-36” due to potential for prussic acid poisoning and nitrate toxicity with the right conditions
  • Buckwheat
    • Extremely rapid growth
    • Soil health benefits: suppresses annual weeds and attracts beneficial insects
  • Millet
    • 5 types commonly used in cover crops
    • Soil health benefits: nutrient scavenger, erosion preventer
    • Drought and heat tolerant
    • Good option for grazing or forages if managed correctly, potential nitrate toxicity, some may have prussic acid potential. 
  • Sun Hemp
    • Fast growing tropical legume
    • Soil health benefits: fixes nitrogen, substantial biomass growth, potential to kill soil-borne pathogens
    • Good option for grazing sheep or goats

 

Cover crops are a critical tool for farmers. SHP supports healthy cover crop adoption that is sustainable and works for the farmer. The SHP field team is a resource in helping SHP farmers understand how to adapt to cover crops in their geography.