Response to defoliation

1
Response to defoliation

• What is defoliation ??????????????
• Grazing
• Cut
• What are feature in response to defoliation ?
• Frequency ??????? ??????????????????????????????
  ?? / ???
• Intensity ??????????????????????? / ???
• Time in relation to growth stage of pasture
  ?????? ????????????????????????????????????

2
Structure of grass plant
apical / flower primordia
culm
bud tiller primordia
crown
3
STRUCTURE OF LEGUME PLANT
shoot with flower
crown
root with nodule
4
Sward dynamics
Growth new tissue added
Green herbage
Senescence
Decay dead herbage removed by worms
micro-organisms
Dead herbage
Pasture production tissues eaten by stocks
5
New pasture growth
Growth / production (kg DM/ha)
Decay
Net pasture production
900 - 1200
Pasture mass (kg DM/ha)
6
Gumboot technique

• Graze the pasture depending on the availability
  of the herbage and the recovery of the pasture
  after grazed.

7
Grazing vs. Cutting

• Selectivity by animal
• species preference or palatability
• plant parts leaf is more preferable to stem
• Trampling
• Excretion
• Animal behavior grazing vs. browsing

8
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• ??????????????????????????????????????????? ?.
  ???????? ?. ????? ? ???????? ???????????????
  moving shed ??????????????????????????????????????
  ?????????
• ??????????????????????????????? ?.??????? ?.
  ?????????? ???????????????????????????????????????
  ???????????????????????????? ?????????????????????
  ?

9
Plant response to defoliation

• Reserved carbohydrate in stubble
• Effect on growth of root and shoot bud
• LAI to intercepted light
• Mortality of the sward tiller density,
  coverage
• Climatic factors eg. rain, soil moisture,
  temperature ect.

10
Effect of defoliation to physical environment

• grazing regimes
• water run off
• water penitration
• evaporation
• wilting after drought
• frost damage
• growth form

linient less high less quicker less less change
heavy higher less higher less more tillering
11
How do plant survive after defoliation ?

• Less intensity ie removal of leaves or bud
  primordia is not so severe
• Capacity of plant to form new shoot and leaf
• Recruitment through seed
• Recruitment through stolon and rhizome

12
Differences in defoliation intensity are due to

• Cutting height
• Selective grazing
• physical and anatomical form of plant
• chemical substance silica, coumarin
• animals are get use to
• seasonal and palatability of plant

13
Pasture growth vs production under defoliation
regimes

• Desmodium Cynodon
• Cutting intervals intortum dactylon
• (weeks) (ton/ha/yr) ()
• 4 4.2 62 7.0
• 8 6.5 72 9.1
• 12 8.0 81 10.0
• mean over 3 cutting height 3.8 , 7.5, and 15
  cm
• source Jones, R.J. 1973

14
Effecting of defoliation on regrowth and plant
form

• crown , root and LAI
• increase leaf content leafy sward
• enhance branching if cut at juvinile stage
• severe defoliation will decrease reserved CH2O
  and plant vigor
• after cut there will be enough leaf to intercept
  95 of light is desired
• the more Total Available CH2O is better

15
The relationship between intake and pasture
characters
Nutritional limited
Non nutritional limited
Pasture intake (kg DM/ha)
Pasture weight (kg DM/ha), height (cm), post
grazing mass (kg DM/ha)
16
Non-nutritional limited vs Nutritional limited

• pasture structure
• pasture allocation
• grazing behavior of animal
• diet selection
• grazing time
• bite size
• rate of biting

• pasture nutritional quality
• digestibility
• legume component