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Grass Growth and Pasture Management

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					Grass Growth and Pasture
      Management


            Part of the Ruminant
              Livestock: Facing
              New Economic
              Realities Meetings
      Grass Plant Tillers
                                        Seed head




                               Lead
                                                    Rhizome
                               Tiller
                                                    Tiller

                      Crown
                      Tiller




Source: L.L. Manske
North Dakota State
University
            Grass Physiology
• Cool season grasses initiate flower buds on the
  crown when exposed to low temperatures and
  long nights.
• Carbohydrates are stored late in the growing
  season (fall management is critical).
• In the spring, new growth is initiated from the
  crown using carbohydrate reserves stored in the
  roots, rhizomes, stolens, and/or stem bases.
• As day length increases throughout spring, at
  some point a flowering response is triggered.
          Grass Physiology
• Not all tillers produced by the plant are
  reproductive tillers, but…
• Because reproductive tillers grow taller than
  the vegetative tillers they shade out the
  vegetative tillers and in addition…
• As seed heads develop they produce plant
  hormones that retard the development of
  other vegetative tillers
           Grass Physiology
• Removing the seed head by grazing or
  clipping will promote development of
  vegetative tillers
• Because most cool season grasses require
  cool temperatures and long nights to once
  again develop reproductive tillers, after seed
  heads are removed, vegetative growth is
  produced for the remainder of the year
     UNDERSTANDING PLANT
           GROWTH
•   Light
•   Roots/Carbohydrate Reserves
•   Temperature
•   Water
•   Fertility/Nutrients
PLANT REGROWTH AFTER
HARVEST

• From Carbohydrates Produced by
  Remaining Leaf Area

• From Carbohydrate Reserves
   Defoliation Stresses Forage
              Plants
• Reduces or eliminates photosynthesis

• Stops nutrient uptake from the soil

• In legumes, nitrogen fixation stops within
  hours of harvest
         Leaf Removal vs. Root Growth
          10%
          20%
          30%
          40%
 % Leaf 50%
Removed
          60%
          70%
          80%

                0            20        40       60          80   100
                          Percentage Root Growth Stoppage
   Source: Crider, 1955
         Grazing Principle

For Rapid Regrowth:
Take Half
Leave Half

(By weight/volume: recognize forage is
  denser towards base of plant)
    What You Leave Behind…
• Affects re-growth rate
• Affects root growth
• Affects soil temperature
• Affects organic matter
• Affects water infiltration rate and water-
  holding capacity
• Affects nutrient cycling
        Animal Intake and Pasture
                Residual
• Forage Systems Research Center work has found
  about 80% of the variation in grazing intake is
  correlated with post-grazing residual.
• When forage mass drops below a critical level,
  intake is restricted
• In other words, the reason the top end of graziers
  are getting better animal performance compared to
  lower end graziers is because they know when to
  get their livestock out of a pasture paddock.
       Managing Grazing Heights:
      Pure or dominant grass stands
Species              Pre-graze inches   Post-graze
                                        inches
Perennial Ryegrass   6-7                3
Orchardgrass         8-10               3-4
T. Fescue (E+)       5-6                1-2
T. Fescue (E-)       8-10               3-4
Brome grass          Pre or late        2-3
                     jointing
Timothy              Pre or late        4
                     jointing
    Managing Grazing Height
Grass                Legume      Mixtures
Species              Pre-graze   Post-graze
                     inches      inches
Bluegrass/w clover 4-5           1-2

OG/L clover          6-8         2-3
T fescue/L clover    5-8         1.5 - 2
Alfalfa with grass   bud         2-3
Red clover with      bud         2-3
grass
         Grazing Principle

•Provide plants with adequate rest period
  to re-grow to correct grazing height
  Relationship of rest period to pasture
  mass during periods of rapid vs. slow
  growth

Lbs.                                  Optimum

DM / acre                                Rest
                                        Period




            0     5         10        15      20     25
                Period of fast plant growth (days)
                                                          Source: Craig
                                                          Saxe, University
            0     10        20       30      40      50   of Wisconsin
                Period of slow plant growth (days)        Extension
        Rest Period Management
• Paddock number determines flexibility and the
  degree to which the grass plant can be managed.
• For example in a 4 paddock system if my goal is
  not to graze the new re-growth until 8 inches, then
  my rotation flexibility is 12-16 days in the spring
  and 28 to 32 days in the summer
• In a 10 paddock system, rotation flexibility is 10 to
  30 days in the spring and 50 to 70+ days in the
  summer
• More paddocks can result in higher utilization rates
  MANAGEMENT TO OPTIMIZE
  PLANT GROWTH
• Avoid production of seed heads, keep the
  plant vegetative
• Maintain leaf canopy (residual
  management)
• Recharge plant root reserves
• Vary rest periods by season and rainfall
• Frequent shifts of short duration
• Provide adequate soil nutrients
 Growing Season Management
• The reason behind using rest periods and
  residual management is to increase
  productivity and to put the grazier in the
  position to extend the grazing season
  through:
• Quicker green up in the spring
• Quicker recovery from drought
• Fall/Winter grazing?
Management Changes?

				
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posted:5/29/2012
language:English
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