Understanding Forage Plant Growth and Grazing Management

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Understanding Forage Plant Growth and Grazing
Management

• Chris Teutsch
• Southern Piedmont AREC
• Blackstone, VA

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Starting and Stopping Grazing
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Topics

• Physiology vital processes taking place in the
  plant
• Morphology form and structure of the plant
• How the physiology and morphology of plants
  relate to grazing management

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Photosynthesis

• Converts light energy to chemical energy
• light, chloroplast
• CO2 H2O SUGAR O2
• Major Pathways
• C3 (cool-season grasses)
• adapted to cooler temperatures
• growth in spring and fall
• C4 (warm-season grasses)
• more efficient at higher temperatures
• more efficient water use

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Growth Curves for Common Forages
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Plant Morphology

• Grasses
• bunch type
• tall fescue, orchardgrass
• tillers upward forms clump
• sod formers
• bermudagrass, Ky Bluegrass
• has rhizomes or stolons
• forms dense sod
• Growth Habit
• erect hay
• prostrate pasture

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Structures of Grasses Legumes

• Root System
• Legume tap
• Grass fibrous
• Rhizome
• stem below soil
• stores CHO
• spreading
• Stolon
• stem above soil
• stores CHO
• spreading

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Defoliation

• What is needed for regrowth?
• ENERGY
• Where does this energy come from?
• leaf area remaining
• stored carbohydrates

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Nonstructural Carbohydrates

• Stored substances that provided energy for
  regrowth and persistence
• Factors affecting carbohydrate reserves
• sunlight, water, nutrients, CO2, temperature
• environmental stress, defoliation

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Location of Carbohydrate Reserves
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Carbohydrate Cycling in Alfalfa

• 100 dependent on stored CHOs
• Decrease until 6-8
• Return to precut level by early bloom
• Allow 30-35 d rest
• Cut at 2 inches
• most legumes have similar cycle

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Grass Regrowth

• Reproductive Growth
• Cool-season grasses once per year
• Warm-season grasses repeatedly
• Collar present no regrowth
• Still photosynthesizing
• Combination of leaf area and CHOs

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Carbohydrate and Leaf Area Interactions
Rotational Grazed
Continuously Grazed
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What is going on Underground?

• Removing 50 of shoots stops root growth
• Single removal of 90 of shoots stopped root
  growth for 17 days
• 3 clippings/week root growth never resumed
• Root growth did not stop when 40 or less of
  shoots were removed

(F.J. Crider. 1955. Root-growth stoppage. USDA
Tech. Bul. 1102.)
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Morphology and Physiology in Relation to Grazing
Management
High Leaf Area High NSC Higher Yields
Faster Recovery
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Botanical Composition

• Low cutting height favors plants more dependent
  on CHOs for regrowth
• High cutting height favors plants more dependent
  on leaf area for regrowth

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Conclusion

• Understanding forage plant growth allows
  producers to maximize pasture production and
  forage quality while maintaining botanical
  composition and persistence of perennial pasture
  species.

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Starting and Stopping Grazing