Cover Crop Seeding and Management

  • Cover crop selection is somewhat dependent on the environment and growing season.
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  • Broadcasting by air or ground and drilling are primary methods of seeding.
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  • Proper cover crop termination is important for the future success of the following cash crop.
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Cover Crop Selection

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A number of different crops are potentially available for use as a cover crop depending on the growing season and environment where the crop is to be planted. Cover crops can include legumes (red, berseem, mammoth red, white, alsike, crimson, and sweet clovers, annual medics, cowpea, hairy vetch, alfalfa, birdsfoot trefoil), grasses (annual ryegrass, cereal rye, oats, wheat, sorghum-sudangrass, triticale, barley, rye), brassicas (oilseed radish, mustards, forage turnips, rape, canola) and other broadleaves such as buckwheat. Each species has benefits and disadvantages and must be managed accordingly. The legumes can potentially provide additional nitrogen (Table 1). An excellent tool to help determine which cover crop is best suited for a field is The Cover Crop Decision Tool - Field Crops, which is available from the Midwest Cover Crops Council (www.mccc.msu.edu/index.htm). 

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Methods for Seeding Cover Crops

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Several methods and variations within the methods can be used to seed cover crops. The weight and size of cover crop seeds can vary greatly; therefore, the seeding equipment and management practices should be matched with the seed.1

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  • Broadcasting by Air - Best adapted to larger seeded species, allows for overseeding or interseeding into existing crops, especially when soils are too wet for ground seeding (Figure 1).
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  • Ground-based Broadcasting - Most used seeding method and tends to be a very accurate. Spinners, drop tubes, or air pressure equipment can be used. However, due to heavier seeds traveling farther than lighter seeds the metering system should be set appropriately to develop the desired seeding pattern. 
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  • Incorporation - If possible, better stands are produced with light incorporation.
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  • Drilling - In the central Corn Belt, drilling after harvest is the preferred time and type of seeding. The legume/grass box on a drill works well for small-seeded cover crops while the standard box is best adapted to larger seeds. No-till operations are a good fit for drills. 
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Regardless of the seeding method, seeder calibration is necessary for each type of seed. Seeding rates for various cover crops are provided in Table 1.2 In many situations, combinations of two or more cover crop species are seeded together; therefore, The rate for each species within the combination is generally less than their single rate recommendations. Seeding rates may also be different for geographical areas, as an example, oilseed radish alone is being seeded in the 8 - 10 lb/acre range in some areas. Local agronomists can help with seeding recommendations. The steps to follow for ground-based calibration are:
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  • Determine the application rate in (lb/acre).
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  • Fill the seeder.
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  • Determine the spread width knowing the spread width will be less than the actual width the seeds are spread.  Allow for consistent overlap.
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  • Set the seeder opening to the desired setting.
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  • Operate the seeder in a stationary location and collect seed being applied for one minute.
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  • Calculate the area that would have been seeded (if moving) and use the formula: length in feet of area seeded (tractor speed converted to distance traveled in one minute) X spread width in feet/43,560 = acres seeded.
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  • Divide the pounds collected by the area seeded to obtain the actual seeder output in lb/acre.
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  • Make adjustments to tractor speed and/or seeder setting and repeat steps 5-7 to change application rate to the desired amount.1
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Figure 1. Aerially seeded annual ryegrass and radish.
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  Table 1. Cover Crop Seeding Rates and Depths, Life Cycle, and Nitrogen Values. 
Species
 Seeding Rate
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 (lb/acre)
 Seeding Depth if Planted (inches)
 Nitrogen Valuea
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 (lb/acre)
 Life Cycle
 Annual medic
 10 - 39
 .25 to .5
 40 - 100
Summer annual
 Berseem clover
   9 - 20
 .25 to .5
 60 - 90
Summer annual
 Crimson clover
 12 - 20
 .25 to .5
 50 - 60
Summer annual
 Field peas
 70 - 150
 1.0 to 2.0
 30 - 100
Summer annual
 Hairy vetch
 25 - 40
 .5 to 2.0
 60 - 180
Winter annual
 Mammouth red clover
 8 - 15
 .25 to .5
 60 - 70
Biennial
 Sweetclover (yellow) (SC)
 8 - 15
 .25 to .5
 70 - 90
Biennial
 Alfalfa
 9 - 25
 .25 to .5
 50 - 150
Perennial
 White clover
 5 - 7
 .25 to .5
 60 - 100
Perennial
 Medium red clover (MRC)
 10 - 15
 .25 to .5
 60 - 70
Perennial
 Alsike clover
 4 - 10
 .25 to .5
 60 - 70
Biennial/
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Perennial
 Birdsfoot trefoil
 5 - 10
 .25 to .5
 40 - 100
Perennial
 60/40 Mix MRC/SC
 8 - 15
 .25 to .5
 60 - 90
Biennial/
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Perennial
 Buckwheat
 36 - 60
 .25 to .5
 NA
Summer annual
 Forage turnips
 3 - 5
 .25 to .5
 NA
Summer annual
 Oats
 34 - 68
 1.0 to 2.0
 NA
Summer annual
 Oilseed radish
 15 - 25
 .25 to .5
 NA
Summer annual
 Rape
 3 - 8
 .25 to .5
 NA
Summer annual
 Annual Ryegrass
 15 - 25
 .25 to .5
 NA
Winter annual
 Barley
 48 - 96
 1.0 to 2.0
 NA
Winter annual
Cereal Rye
 28 - 112
 .5 to 1.0
 NA
Winter annual
 Triticale
 60 - 120
 .5 to 1.0
 NA
Winter annual
 Wheat
 60 - 120
 .5 to 1.0
 NA
Winter annual
aDepends on cover crop density and rate of decomposition.
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Source: Mutch, D.R. and Martin, T.E. Michigan field crop ecology - cover crops. What are cover crops? (Managing Cover Crops Profitably. Sustainable Agriculture Publications - USDA).
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Time of Seeding

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Overseeding or interseeding should occur when there is enough available light for the cover crop seed to germinate and become established, but late enough that it does not compete with the growing crop. In the northern U.S. and Canada, recommendations based on research suggest that legumes should be seeded between corn growth stages of V-4 and V-6, while annual ryegrass should be seeded between V-6 to V-8.2 In the central Corn Belt overseeding in corn generally occurs at black layer as the crop begins to senesce. In soybean, overseeding is best accomplished when leaves begin to turn yellow. Overseeding may not be recommended if soils are too dry to adequately establish a stand.

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Frost-seeding occurs when the cover crop is seeded in late winter to very early spring such as red clover being seeded into wheat in March or earlier depending on geographical location. Seeding can also be accomplished pre- or post-season when the cover crop is seeded before a late-season crop or after the prior crop has been harvested.

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Cover Crop Termination

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Chemical control with a tank mix of a Roundup® brand agricultural herbicide product and 2,4-D ester can provide effective control. Applications should be made to the cover crop when its stage of growth is best for control. Individual state recommendations should be followed.

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