Effects of defoliation (cutting or grazing on pasture yield

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Effects of defoliation (cutting or grazing on
pasture yield
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Factors

• Cutting frequency
• Cutting intensity
• Timing
• Selection (grazed pastures)

severity
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Effects of cutting frequency on DM yield and
protein content of Napier
Cutting interval (wks) DM Yield (t/ha) Protein content () Protein Yield (t/ha)
3 (17) 10.8 19.4 2.1
4 (13) 14.4 14.5 2.1
6 (9) 18.7 12.1 2.3
7 (7.4) 19.0 11.0 2.1
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Conclusion

• Short cutting interval low yield, but high
  quality
• Long cutting interval high yield but low quality

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Suitable cutting interval

• Cutting interval giving moderately high yield
  with good quality
• Average 4-6 weeks
• Legumes needs longer interval

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Why does yield decline with frequent cutting?

• Reduction in soluble carbohydrate for regrowth
• Reduction in Leaf Area Index (LAI) for
  photosynthesis
• Retardation of root growth

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Measurement of Pasture Yield

• Two types
• Dry matter on offer yield at any one time
• Production Yield yield over a unit time

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Dry matter on offer

• Use sample quadrats (0.5 m x 0.5 m 1m x 0.5 m)
• Place quadrats randomly in field
• Cut all vegetation in quadrat
• Weigh fresh and dry all or sub sample in oven at
  65oC for 48 hours
• Weigh dried sample
• Convert average weight to kg/ha

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End