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Pasture Ecology

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Pasture Ecology ANSC 110 August 31, 2010 * Environmental stressors drought, cold or excess rainfall Seed disbursal cling to the body of grazing animals and ... – PowerPoint PPT presentation

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Title: Pasture Ecology


1
Pasture Ecology
  • ANSC 110
  • August 31, 2010

2
Pasture Ecology
  • Ecology- Interrelationships of grasses, legumes,
    weeds, and grazing animals with their environment
  • Categories
  • Non-living components
  • Plants that capture solar energy
  • Herbivore/Carnivore consumers
  • Decomposers

3
Why do we care?
  • Some plants are better able to adapt to the
    environment than their neighbors
  • Has a HUGE impact on pasture quality
  • By understanding ecology, we can better implement
    management techniques

4
What influences pasture ecology?
  • Energy
  • Water Temperature
  • Pasture site
  • Space available
  • Competition
  • Grazing habits
  • Plant anatomy
  • Soil characteristics
  • Decomposers/Pests

5
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6
Energy
  • Energy runs the show
  • Free energy in the form of sunlight
  • Manage pasture to maximize sunlight
  • Increase leaves/surface area
  • Increase size of leaves
  • Increase length of growing season

7
Solar Energy
Volume of plants
Area of leaf
Duration of growth
Savory, 1988
8
Energy Through Sunlight
  • Sunlight is single most important influence on
    pasture yield
  • Light collection is influenced by
  • Forage species
  • Leaf angle
  • Canopy density
  • Leaf aging
  • Availability of water and nutrients in soil

9
Competition for sunlight
  • When another plant shades its neighbor, the
    photosynthesis rate of that neighbor declines
  • Competition for sunlight decreases at
  • Early growth in spring
  • Re-growth after grazing/cutting

10
Competitive advantage
  • Sunlight is not like a soil nutrient
  • Must be used instantaneously
  • Once gone, gone forever
  • Position of leaves gives plants the competitive
    advantage
  • Leaves that are above the canopy will get more
    sunlight than those below

11
Water
  • Rainfall is primary water source for pastures
  • Irregular rainfall ? deficient or excessive soil
    water
  • Direct effect on plant productivity and
    persistence

12
Drought
13
Drought
  • Plant leaf area decreases
  • Plant root growth increases
  • Decreased ability to take up nutrients

14
Drought
  • Ability of legumes to fix N decreases
  • Carbohydrate storage supplies decrease
  • Nutrient levels highest at surface

15
Wet conditions
  • Too wet ? plant growth slows
  • Water fills soil pockets, excluding oxygen needed
    by plant roots
  • Fungal root disease organisms will thrive and
    damage roots
  • Longer recovery periods after wet conditions are
    needed before grazing

16
Temperature
  • Second most important influence
  • Plants are adapted to certain climatic conditions
  • 68 F
  • Plants that can adapt to temperature fluctuations
    will do better

17
Temperature
  • Mean annual air temperature for our zone (Zone D
    in textbook) is 58 F

18
Pasture Site
  • Forage crops cannot escape the locations in which
    they are growing
  • Location influences affect pasture composition
    and growth
  • Important factors to consider
  • Elevation
  • Soil type
  • Drainage
  • Slope and exposure

19
Space Available
  • Space within pasture is limited
  • Bare spaces allow growth of unwanted weeds
  • As space becomes more limited so does
  • Moisture
  • Light
  • Nutrients needed for growth

20
Competition
  • When all necessary growth factors are in
    abundance, competition doesnt play a part in
    pasture ecology
  • Low supply of one vital nutrient will cause
    competition among forage species

21
Competition
  • Water
  • Nutrients
  • Light
  • Carbon Dioxide
  • Oxygen
  • Environmental stressors
  • Means of pollination/seed disbursal

22
Competition
  • Success of a single plant depends on how well its
    characteristics
  • Match the demands of the environment
  • Allow it to cope with stresses as compared to
    neighboring plants
  • Increase the competitiveness of the desired
    species and/or decrease the competitiveness of
    the undesirable species

23
What makes a plant a successful competitor?
  • The plant that can
  • Draw on the limited factor
  • Do so quickly
  • Usually able to grow more roots and leaves
  • Adaptable to several environmental conditions

24
Grazing Habits
  • Intensity and frequency can have a tremendous
    affect on competitive ability of many pasture
    plants
  • Pasture species vary greatly in their tolerance
    to grazing

25
Grazing Horses
  • Animals ? more complex pasture
  • Selective grazing
  • Manure and urine
  • Treading - Walking, running, jumping, lying down,
    scratching, pawing

26
Management
  • Plant height especially during leaf development
    and elongation
  • Grazing frequency
  • Grazing intensity
  • Soil fertility

27
Management
  • Weedy pastures
  • Understocked lax grazing
  • Overgrazing

28
Management
  • Clover and grass
  • High N from urine and fertilizer ? grass growth,
    shading of clover
  • More frequent grazing ? no shading of clover,
    increased competitive ability

29
Overgrazing
  • Not necessarily number of animals
  • More a function of the time that animals are
    exposed to plants
  • An overgrazed pasture is one that grows from root
    energy rather than solar energy
  • Continuous grazing or inflexible rotational
    grazing without enough paddocks

30
Plant Anatomy
  • Plant roots have a huge effect on pasture
    productivity
  • Water absorption
  • Nutrient absorption
  • Nutrient storage
  • Root temperature soil temperature
  • Rhizomes or stolons?
  • Taproot?

31
Plant Anatomy
  • If overgrazing occurs, regrowth depletes food
    reserves and weakens the plants
  • Methods plants use to cope with being grazed
  • Spines, thick hairs, waxes, tough leaves
  • Chemicals to deter grazing

32
Grazings effect on roots
  • If pasture is grazed during adverse conditions,
    animals will preferentially avoid weeds
  • About ½ of pasture plant growth is in the roots!

33
Soil Characteristics
  • Microorganisms
  • Earthworms
  • Nematodes
  • Nutrients

34
Soil Characteristics
  • Various soil nutrients levels favor different
    plant species
  • Knowing general fertility requirements of various
    pasture plants has practical application

35
Microorganisms
  • Found near the roots
  • Presence of soil organisms helps reduce nitrogen
    loss through leaching
  • Root area of soil is different because
  • Release of organic materials from roots
  • Uptake of nutrients by roots improved

36
Rhizobium Bacteria
  • Nodulate the legume root
  • To form a small knoblike outgrowth on the roots
    of many leguminous plants
  • Symbiotic relationship with plant
  • Requires certain soil nutrients and pH

37
Earthworms
38
Earthworms
  • Pasture production can be as much as 25 higher
    on earthworm-containing fields
  • Aerate and loosen soil
  • Incorporate dead pasture plants
  • Break down manure quickly
  • Eat nematodes that could harm clover roots

39
Earthworms
  • Move 20-30 tons of soil per acre per year!
  • Application of urea (fertilizer) can cut
    earthworm numbers in half
  • Use ammonium nitrate instead
  • Soil pH below 5.6 is unfavorable
  • Herbicides, insecticides can kill them
  • Need plant cover (no bare soil)

40
Nematodes
  • Beneficial and important
  • Lead to rapid decay and incorporation of organic
    matter in the soil
  • Nutrient cycling
  • Feed on bacteria, fungi and soil protozoa
  • Pathogenic forms are kept in check by predatory
    nematodes (in soils that are in good condition)

41
Pests
  • Weeds
  • Forbs (example pigweed)
  • Noxious weeds (causes injury, has a bad taste or
    is poisonous)
  • Insects
  • Grasshoppers, locusts, crickets, aphids, etc.
  • Control by not overgrazing, provide birdhouses,
    add poultry to pasture

42
Pests
  • Diseases
  • About 45 disease affect pasture plants
  • Mixed populations is best control
  • Avoid overgrazing
  • Rabbits, hares and rodents
  • Favored by overgrazing
  • Encourage abundant diversified wildlife (i.e.
    foxes, owls, eagles, even snakes)

43
Things to Remember
  • Only a slight change in a particular
    environmental factor may determine death or
    survival of an individual plant
  • Good management decisions have major impacts on
    pasture productivity, persistence, and livestock
    performance
  • Many factors that influence pastures can in some
    way be affected by management
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