Grass Physiology ó Grazing Management · 2017. 6. 29. · A prescription for grazing: üPasture...
Transcript of Grass Physiology ó Grazing Management · 2017. 6. 29. · A prescription for grazing: üPasture...
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Geoff Brink USDA – Agricultural Research Service
Grass Physiology ó
Grazing Management
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Bunch Rhizomatous Orchardgrass Reed canarygrass Tall fescue Smooth bromegrass Meadow fescue Kentucky bluegrass Timothy Quackgrass Festulolium Meadow bromegrass Ryegrasses
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Primary tiller
Axillary bud Growing point
Orchardgrass (bunch)
Secondary tillers
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Quackgrass (rhizomatous)
Growing point
Primary tiller
Rhizome
Secondary tiller
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Growing point – the leaf producing “engine”
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1st leaf 2nd leaf
Orchardgrass (bunch)
3rd leaf 4th (1st) leaf
5th (2nd) leaf 6th (3rd) leaf
7th (4th) leaf
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Days of growth
Pasture production
0 10 20 30 40 50 60
Vegetative stage 10 – 16 in. tall 3 – 4 leaves
(max photosynthesis)
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Days of growth
0 10 20 30 40 50 60
Mature stage > 20 in. tall 4 – 5 leaves
(senescence)
Pasture production
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Carbohydrates Produced by leaves; stored in stem bases, rhizomes, and roots.
• Keep plant alive during stress (after grazing, night, drought, winter). • Needed to grow new leaves, tillers, roots.
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The plant’s “to-do list” after grazing
3. Grow new tillers
1. Produce new leaves
2. Replace fine roots
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3 – 4 in. residue
leaf area
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1 – 2 in. residue
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Residue (in.)
No. grazing events
Average rotation time
(days)
Average rotation yield
(lb/acre)
Annual yield
(lb/acre)
Date grass reached 12 in.
next year
1½ 4 44 1250 5000 May 11
3 6 32 900 5400 May 4
6 6 24 750 4500 April 28
Residue effects on vegetative orchardgrass
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0
50
100
150
200
250
6 3 1
Tillers (no./ft2)
Residue effects on meadow fescue survival
Residue height (in.)
25% loss
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Residue (in.)
No. grazing events
Average rotation (days)
Annual yield (lb/acre)
3 3 73 6400
6 3 62 5700
12 3 60 5500
Residue effects on mature orchardgrass.
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Residue height and hay harvest
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4 in. residue 2 in. residue
Meadow fescue after cutting for hay for 2 years.
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The dog days of summer,
and the perils of winter.
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0
250
500
750
1000
1250
1500
May Jun Jul Aug Sep Oct
6"12"
July grazing ht. Yield (lb/A)
Grazing frequency effects on orchardgrass yield
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600
700
800
900
1000
1100
1200
May June August
6 in.2 in.
Residue height of last grazing (October) and orchardgrass yield in 2012.
Yield (lb/A)
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Wrong time
Too often
Too short
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A prescription for grazing:
ü Pasture productivity and persistence of vegetative grass will likely be reduced in the current season and/or the next by grazing to a short residue.
ü The negative effects of grazing vegetative grass to a short residue will be amplified when grass is stressed (previous grazing, drought, winter).