Grass Growth and Pasture Management Part of the Ruminant Livestock: Facing New Economic Realities...
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Transcript of Grass Growth and Pasture Management Part of the Ruminant Livestock: Facing New Economic Realities...
Grass Growth and Pasture Management
Part of the Ruminant Livestock: Facing New Economic Realities Meetings
Grass Plant Tillers
RhizomeTiller
CrownTiller
LeadTiller
Seed head
Source: L.L. ManskeNorth 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
0 20 40 60 80 100
80%
70%
60%
50%
40%
30%
20%
10%
% LeafRemoved
Percentage Root Growth StoppageSource: 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 jointing
2-3
Timothy Pre or late jointing
4
Managing Grazing Height
Grass Legume Mixtures
Species Pre-graze inches
Post-graze 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 grass
bud 2 - 3
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
Period of fast plant growth (days)
Period of slow plant growth (days)
0 5 10 15 20 25
0 10 20 30 40 50
Lbs.
DM / acre
Optimum
Rest
Period
Source: CraigSaxe, Universityof WisconsinExtension
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?