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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

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
daicon radish
Not a traditional radish

Being marketed as biological compaction relief

Some evidence of increased microbiological activity as a cover crop

Daicon Radish
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 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
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
  • Bottom line
  • Seed and establishment not cheap
thank you