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4 21 cover crops

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  • 1. Cover Crops
  • 2. Introduction
    • Definitions:
      • Cover crop – a crop planted between main crops to prevent erosion or to be plowed in to enrich the soil
      • Green Manure – a growing crop that is plowed in to enrich the soil
    • The backbone of a sustainable crop system
  • 3. Legumes
    • Able to “fix” nitrogen
    • Nitrogen in atmosphere unavailable for plant use
    • Bacteria in nodules converts inert nitrogen to nitrates
    • Extra nitrogen fertilizer is not required
    • Examples: peas, beans, alfalfa & clovers
  • 4. The Industrial Model
    • Crop planted in spring
    • Pesticides used to control insects and weeds
    • Crop harvested in fall
    • Land left fallow in winter
    • Land fertilized in late winter
    • Land sprayed with herbicides in early spring
    • Crop planted in spring
  • 5. Benefits of Cover Crops
    • Prevent Erosion
    • Improve soil quality
    • Suppress weeds
    • Reduce insects
    • Prevent nutrient leaching
  • 6. Prevent Erosion
    • Roots hold topsoil in place
    • Water & wind strip topsoil from land
    • Sediment clogs waterways
      • Major water pollution problem
    • Tillage exposes soil to erosion
      • Use No-till techniques
  • 7. Improve Soil quality
    • Root depth
      • Deep rooted crops break through compacted subsoils – biological plow
    • Soil aggregates
      • Decomposed organic material (humus) binds mineral portion of soil in stable aggregates
  • 8. Soil quality
    • Soil Organic Matter
      • Replaces organic materials lost in cultivation
    • Soil Fertility
      • Roots of legumes returns fixed nitrogen to the soil
  • 9. Suppress Weeds
    • Cover crops shade soil
      • Blocks sun to low-growing weeds
      • Reduces weed seed germination
    • Residue left after harvest acts as mulch
      • Prevents weed seed contact with soil
    • Allelopathy – some plant roots secrete natural toxins that slow the growth of competitor plants
      • Small grains like ryegrass & sorghum
  • 10. Reduce Insect Problems
    • Provides habitat for diverse insect populations
    • Increases the population of “predator” bugs
  • 11. Prevent nutrient leaching
    • Stops phosphorus pollution from sediment
    • Absorbs excess nitrogen from fertilized crops and returns it in more stable form
  • 12. Cover crop models
    • Winter cover crop
    • Summer green manure crop
    • Living mulch
    • Catch Crop
    • Forage Crop
  • 13. Cover Crop Model
    • Winter cover crop
      • Planted in fall – prevents erosion over the winter
      • Legumes increase soil nitrogen for next summer’s crop
    • Summer green manure crop
      • Plant in late winter - early spring and plow under
      • Increases soil organic matter
      • Legumes add nitrogen
      • Non-legumes smother weeds
  • 14. Others
    • Living mulch
      • Plant vegetables into clover beds
      • Strips of grasses in alley ways between perennial crops
    • Catch crop
      • Plant rye after corn to collect excess nitrogen
    • Forage crop
      • Cover crop grown for grazing
  • 15. Killing cover crops
    • Need to kill the cover crop before you can plant the main crop
      • Pesticide
        • Glyphosate (Round-up) kills all plant material
      • Mowing
        • Mowing at proper stage prevents regrowth
      • Crimping
        • Stalks are bent down and cracked
      • Winter kills
        • Annual cover crops are killed by frost
  • 16. Buckwheat
    • Legume
    • Roots very fibrous but not deep
    • Adds nitrogen to the soil
    • Plant in spring or fall
    • Used to fight weeds
  • 17. Clovers
    • Legumes
    • Live about 2 years
    • Plant in spring or fall
    • Kill & turn under 4 weeks before planting crop
    • Used to
      • Add nitrogen
      • Build soil
      • Resist erosion
      • Fight weeds
  • 18. Cowpeas, soybeans or field peas
    • Legumes
    • Annual
    • Used to:
      • control erosion
      • Build soil nitrogen
  • 19. Sorghum/Sudan grass
    • Very vigorous root growth
    • Used to:
      • Build soil
      • Loosen subsoil
      • Fight pests
  • 20. Winter rye, wheat or oats
    • Winter rye & wheat – grow during the winter
    • Oats and regular wheat grow in spring and fall
    • Annuals (die every year)
    • Extensive root system
    • Grow rapidly in proper season
    • Build soil, fight weeds and pests
  • 21. Root boxes
    • Plant your cover crop
    • Measure weekly:
      • Vegetative height
      • Root depth
  • 22. Wrap - up
    • What difference do you expect in the soil nitrogen levels after the crop is turned under?
    • What do you expect to change when we test the soil again in June?
    • Which plant root structures will penetrate the deepest in the boxes?  
    • How can you protect your garden soil from erosion?

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