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Effects of Cover Crop Management on Corn Production. Brian Jones Agronomy Extension Agent 245-5750 brjones8@vt.edu http://www.valleycrops.cses.vt.edu. Benefits of Cover Crops - Review. Cut fertilizer costs “Fix” atmospheric N (legumes)

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Effects of Cover Crop Management on Corn Production

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Effects of cover crop management on corn production

Effects of Cover Crop Management on Corn Production

Brian JonesAgronomy Extension Agent




Benefits of cover crops review

Benefits of Cover Crops - Review

  • Cut fertilizer costs

    • “Fix” atmospheric N (legumes)

    • Scavenge / redistribute nutrients (grasses, some legumes)

    • How much??

      • Big question

      • Depends on: time of killing, season, etc.

      • More later…

Benefits of cover crops review1

Benefits of Cover Crops - Review

  • Suppress weeds / other pests

    • Smother early emerging annuals

    • Competition for water, light and nutrients

    • Root exudates or compounds provide natural chemical and nematode control (sometimes)

    • Encourage beneficial insects

Benefits of cover crops review2

Benefits of Cover Crops - Review

  • Improve yields

    • Increased infiltration (less runoff)

    • Decrease compaction

    • Improve soil structure

    • Increase organic matter

    • Improve nutrient cycling

Benefits of cover crops review3

Benefits of Cover Crops - Review

  • Prevent erosion

    • Dense roots hold soil in place

    • Prevents the “splash” effect

    • Cover over the winter months

Benefits of cover crops review4

Benefits of Cover Crops - Review

  • Conserve soil moisture

    • Residue increases infiltration

      • Surface and root zone

    • Reduce evaporation from bare soil

    • Must avoid killing too late

      • Problem with mechanical control systems

Challenges of cover crops

Challenges of Cover Crops

  • Main Challenge:

    • Fitting them into your system

    • Have to have the feed…

  • Nutrient cycling

    • How much N? May be variable and will need to test (PSNT)

    • N tie up with high C:N cover crops

      • Rye killed late

    • May not see N until following year

Challenges of cover crops1

Challenges of Cover Crops

  • Cropping challenges

    • Allelopathy may affect cash crop

    • Stand / emergence issues

    • Planting equipment adjustments

    • Mechanically killing for some

    • Good environment for harmful insects

    • Cost of production

Challenges of cover crops2

Challenges of Cover Crops

  • Need to understand these questions with our systems and conditions

  • No perfect cover

    • Depends on rotation, needs, etc.

  • Need local research…



  • Quantify the effects of cover crop species on soil fertility and nutrient cycling

  • Determine how cover crop kill date affects cover crop biomass, corn yield and nutrient cycling

  • Part of a larger study looking at low-input cover crop management

  • Funded by the Shenandoah RC&D Council



  • Project established in 2006 in Rockingham County

  • Planted seven different cover crop treatments in fall of 2006

    • Three replications of each

  • Each treatment was killed at three different timings

    • Residue rolled flat

  • Cover crop biomass, soil samples, and cover samples were taken prior to each rolling

  • Corn was planted no-till after each rolling

    • 0 lbs N applied to corn

  • Whole plot was harvested with chopper and yield determined







  • Timing of killing was based on small grain development:

    • May 10 (boot stage)

    • June 1 (soft dough)

    • June 11 (hard dough)

  • Only talk about data from May 10 and June 1 treatment today

    • Latest that most of us will be planting corn

Results cover crop dm and yield

Results: Cover Crop DM and Yield

Results cover crop dm and yield1

Results: Cover Crop DM and Yield



Daicon radish

Not a traditional radish

Being marketed as biological compaction relief

Some evidence of increased microbiological activity as a cover crop

Daicon Radish



Total n from cover crop

Total N from Cover Crop







Available n from cover

Available N From Cover

  • Total N is not all available for mineralization and crop uptake

    • Loss factors include:

      • Volatilization (loss to atmosphere)

      • Immobilization (tied up by bacteria)

      • Leaching (loss to groundwater)

Available n from cover1

Available N From Cover

  • Volatilization losses

    • Depend largely on whether or not cover was incorporated

    • Without incorporating cover crop in our climate figure approximately 50% loss due to volatilization

Available n from cover2

Available N From Cover

  • Immobilization losses

    • Depend largely on the carbon to nitrogen ratio (C:N) of the cover crop species

    • Low C:N (<25) bacteria quickly break down vegetation making N available immediately

    • High C:N (>25) N will become available, but may not be until the following growing season

      • Also, bacteria will tie up soil N in order to digest high carbon residue

      • Often see this with the yellowing of corn in early spring with high residue

Available n from cover3

Net Loss of PANfrom immobilization

Net gain of PANfrom mineralization

Available N From Cover

Available n from cover4

Available N From Cover

Available soil n

Available Soil N

  • Sampled the NO3-N and NH3-N fraction at the time of kill and corn planting to see how much was potentially available

    • These are highly mobile

    • Most of crop uptake

Available soil n1

Available Soil N

Available soil n2

Available Soil N



Crop response

Crop Response

  • So how much N was actually available to the corn crop from our cover crop treatments?

  • Best observed by looking at the plant itself

    • Ear leaf samples show the % N in the plant at silking and provide a good “in-season” analysis of N uptake

Crop response ear leaf n

Crop Response – Ear Leaf N




Crop response silage yield

Crop Response – Silage Yield









  • Bottom line

  • Seed and establishment not cheap

Economics yield advantage

Economics – Yield Advantage

Economics n advantage

Economics – N Advantage

Economics advantage

Economics – $ Advantage

Thank you



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