Turfgrass Growth and Development

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Turfgrass Growth and Development

• Dr. Matt Fagerness
• KSU Turfgrass Extension

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Outline

• Characteristics of all grasses
• Photosynthetic adaptations among grasses
• Turfgrass ecology
• Turfgrass responses to cultural practices
• Turfgrass responses to stress

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Grasses

• Monocot group of plants literally meaning one
  seed leaf
• Dicots (broadleaf plants) two seed leaves

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Characteristics of Grasses

• Basal growing point (crown), which is surrounded
  by compressed stems and leaves
• Secondary shoots (tillers) arise from the crown,
  not branches from the main stalk (corn vs. wheat)
• Fibrous root system with no discernible taproot
• Parallel veins on leaves (no netlike appearance)
• Flowers are small and non-showy

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Outline

• Characteristics of all grasses
• Photosynthetic adaptations among grasses
• Turfgrass ecology
• Turfgrass responses to cultural practices
• Turfgrass responses to stress

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Warm- vs. Cool-Season Grasses

• What exactly does this terminology refer to,
  aside from the obvious times of year in which
  they thrive?
• Heat tolerance? YES
• Drought tolerance? YES
• Water requirements and use efficiency? YES
• But why? PHOTOSYNTHESIS

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Photosynthesis Review

• Basic formula
• carbon dioxidewaterlight (TAMH) sugaroxygen
• Other key players
• Rubisco enzyme binds carbon dioxide or oxygen
• Chloroplasts organelles in cells where all this
  happens
• Phloem conducting tissue which relocates newly
  made food

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Photosynthesis Cool-Season Grasses
Carbon dioxide
Oxygen and carbon dioxide compete for the same
chemical reaction. If oxygen wins, no food is
produced and photosynthesis is less efficient.
Oxygen
Oxygen
Carbon dioxide
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Photosynthesis Warm-Season Grasses
Carbon dioxide
Chlorophyll containing cells are adjacent to the
phloem. Carbon dioxide is shuttled into these
cells and oxygen is not. Result more efficiency.
Oxygen
Oxygen
Carbon dioxide
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Photosynthesis and Water Use

• Because water is a substrate for photosynthesis,
  more efficient photosynthesis means greater water
  use efficiency and reduced water requirements
• Not coincidentally, warm-season grasses require
  less than do cool-season species

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Water Conserving Turfgrasses
Bermudagrass Zoysia Buffalograss
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Turfgrasses Requiring More Water
Kentucky bluegrass Perennial
ryegrass
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Practical Considerations Summer Turfgrass Water
Requirements

• Most turfgrasses will perform better when
  irrigated. The distinction comes when a species
  can or can not survive without water.
• Buffalograss can survive without any water.
• Bermuda and zoysia can survive extended time
  periods without water with limited visual impact.
• Tall fescue can survive reasonable amounts of
  time without water but will show signs of drought
  stress.
• Perennial ryegrass and bluegrass will die without
  water.

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Outline

• Characteristics of all grasses
• Photosynthetic adaptations among grasses
• Turfgrass ecology
• Turfgrass responses to cultural practices
• Turfgrass responses to stress

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Natural Laws of Plant Ecology

• Competition no two plants can truly have access
  to the same resources. Therefore, there is a
  constant seesaw effect to try to find balance.
• Succession plant communities initially will
  favor one species or group of species but will
  gradually shift to a different, more permanent
  mix.
• Ex. Year 1cropland gets abandoned, Year 10
  weeds and grasses, Year 20-50 pine forest, Year
  50-beyond hardwood forest

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Managed Turfgrass Defies Ecology!

• The way we select and manage turfgrasses is
  against the grain of these laws of ecology
• turfgrass is rarely a climax or permanent species
  in nature (tallgrass prairie a close
  approximation)
• maintenance of turfgrass is artificial and fights
  the natural tendencies of nature
• environmental stress and pest problems in
  turfgrass are natures way of pointing this out
  to us

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Turfgrass is a Limited Perennial

• Most turfgrasses are intended perennial crops
  but plants undergo constant recycling
• Phytomer individual shoot unit, produced
  periodically by a turfgrass plant every 2-4
  weeks.
• When we mow, leaves dont regrow the cut portion
  rather, it is replaced by new phytomer(s)

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Phytomer Pros and Cons

• Pros
• allow turfgrasses to withstand mowing and other
  mechanical injury
• allow for recovery from disease and insect injury
• Cons
• plants act as moving conveyor belts for water and
  nutrients
• we have the option to loop this belt or leave it
  going in one direction

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Turfgrass Community Dynamics

• Turfgrass plants compete for light, water,
  nutrients, and available space. Their competitors
  include
• other turfgrass plants (planting density is
  critical)
• weeds
• other plants (shrubs, trees, etc.)
• debris (leaves, piles of clippings)

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Seed Label
Weedy grass seed introduces competition to a
turfgrass stand.
Good Not so Good
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Outline

• Characteristics of all grasses
• Photosynthetic adaptations among grasses
• Turfgrass ecology
• Turfgrass responses to cultural practices
• Turfgrass responses to stress

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Mowing- What Does It Do?

• Decreasing mowing height
• increases shoot density (good for greens)
• increases tiller number per unit area
• decreases leaf width
• reduces root growth and root depth
• increases leaf chlorophyll content
• decreases total leaf area (why shorter areas
  appear to be a lighter shade of green)

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Whats in the Bag? Primary Turf Nutrients

• Nitrogen - Used for above-ground growth and good
  green color (soil mobile, nitrate contamination)
• Phosphorus - Used for root growth and formation
  of seeds and fruit (less mobile in soil but can
  contaminate watersheds like nitrate)
• Potassium - Used for basic plant growth and helps
  plants withstand stress (soil mobile)

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Turf MicroNutrients

• Iron- deficiencies can be noticeable in very high
  pH soils
• Chlorine- provides balance for ions like
  potassium
• Boron
• Molybdenum
• Manganese
• Copper
• Zinc

Act as chemical cofactors (catalysts) for plant
enzymes
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Soil Nutrient Cycling
We return valuable nutrients to the soil when
clippings are recycled.
NH4
NO3
NO3
NO3
Fertilizer
NO3
NH4
NH4
NO3
NO3
Soil microbial pool of N
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Irrigation Tips - Soil Wetting
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Irrigation Tips - Turf Use
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Irrigation Tips Practical Considerations

• Deep infrequent irrigation is ideal but only if
  root growth can match it.
• Golf greens in summer have declining root systems
  so irrigating too deep exceeds where the roots
  are.

Spring Summer Fall
Shoot growth Root growth Irrigation amount
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Outline

• Characteristics of all grasses
• Photosynthetic adaptations among grasses
• Turfgrass ecology
• Turfgrass responses to cultural practices
• Turfgrass responses to stress

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Types of Environmental Stress

• Drought stress
• Heat stress
• Cold stress
• Shade stress
• Salinity stress
• Air stress

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Drought Tolerant Turfgrasses
Bermudagrass Tall fescue Buffalograss Zoysia
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Kansas Turfgrasses Most Sensitive to Heat and
Drought
Kentucky bluegrass Perennial
ryegrass
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Drought Stress

• Drought tolerant turfgrasses might be better
  termed drought avoiding turfgrasses
• most water taken up by plants is transpired
  through the leaves (turgidity and cooling)
• the longer turfgrass plants can acquire water
  during drought, the more they can resist high
  temperatures
• warm-season grasses and tall fescue have deeper
  root systems than do drought sensitive species

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Heat Stress

• Heat stress is often confused with drought stress
  but is usually more damaging to turfgrass plants
• drought in the absence of high temperatures gives
  turfgrasses the chance to recover successfully
• heat stress, even when water is plentiful, can
  still result in permanent damage to sensitive
  species
• Why? Key proteins are denatured in extreme heat.

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Cold Stress

• Possible in both warm and cool season turfgrasses
• Types of cold stress
• desiccation (limited by snow cover)
• intercellular (within) freezing (highly lethal)
• intracellular (between) freezing (worse with
  traffic)
• Warm-season turfgrasses are often tricked by
  early spring warmth. Defenses to subsequent cold
  snaps are removed and injury can occur.

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Winter Injury in Bermudagrass
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Shade Stress

• Can be caused by many things
• trees
• fallen leaves
• foreign objects
• Symptoms
• reduced shoot density
• longer, thinner leaves reaching for the light
• diminished root system

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Species Perform Variably in Shade

• Warm-season grasses suffer in shade
• prefer highly efficient levels of photosynthesis
• Fescues perform best in shade
• fine fescues are more shade tolerant but tall
  fescue presents the total package

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Salinity Stress

• Rarely a direct stress to turfgrass plants but
  often results in drought stress
• Caused by
• high cation (calcium, magnesium, sodium) levels
  in soil or in applied irrigation water
• Effectively reduces soil water available to
  turfgrass plants

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Water Follows a Salt Gradient
When soil water is high in salt, there is no
direction for it to go!!
Soil Roots Leaves
Salt
Salt Salt Salt Water Water Water
Salt Salt Salt Salt Salt Water
Water Water Water Water Water
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Air Stress

• Not a true environmental stress but refers to the
  effects of low air movement
• often most prominent on putting greens
• increased in summer
• decreased transpiration and increased canopy
  humidity
• often manifested as heat stress or disease
  outbreaks
• fans and partial or complete tree removal can
  make a huge difference

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