Download Turfgrass Physiology for the Sports Turf Manager

Turfgrass Physiology for
the Sports Turf Manager
Tony Koski
Extension Turf Specialist
Colorado State University
Fort Collins, CO
http://csuturf.colostate.edu
[email protected]
What will we talk about?
• Photosynthesis…why it’s important for the sports
turf manager to understand
• The difference between warm-season and coolseason grasses (and weeds)…and why it
matters…for weed control, fertilization, irrigation,
shade tolerance, and where you plant them?
• What plant hormones are…why they are
important…and how/why we manipulate them
for our benefit?
• Why biostimulants sometimes work…and
sometimes don’t (or it seems that way, anyway)?
Some Sound-Alike Definitions
Photosynthesis
Harvesting of light energy and conversion into a usable chemical
form of energy
Respiration
Use or oxidation of stored carbon compounds to provide energy for
growth and plant maintenance
Photorespiration
Reduction in carbon fixation capability seen in C3 plants when
internal leaf oxygen levels increase
Transpiration
Movement of water from the soil through the plant, being lost
through the stomates as water vapor
What will we talk about?
• Photosynthesis…why it’s important for the
sports turf manager to understand
• The difference between warm-season and coolseason grasses (and weeds)…and why it
matters…for weed control, fertilization, irrigation,
shade tolerance, and where you plant them?
• What plant hormones are…why they are
important…and how/why we manipulate them
for our benefit?
• Why biostimulants sometimes work…and
sometimes don’t (or it seems that way, anyway)?
CARBON
DIOXIDE
Carbohydrates
“sugar”
Stored Energy
Photosynthesis >>>>>> Energy
• Growth (leaves, roots, rhizomes,
stolons, tillers, flowers, seed)
• Wear/traffic tolerance… and
recovery
• Nutrient absorption
• Nitrogen metabolism
• Amino acid, protein production
• Hormone production
• Heat, cold, drought, salinity
tolerance
• Disease resistance
Temperatures Favoring Photosynthesis
and Dry Matter Production
C3 Grasses
60-77 F (crown temperature)
C4 Grasses
85-117 F (crown temperature)
What Can the Turf Manager do to Favor
Photosynthesis?
M OWING A FFECTS
R OOT G ROWTH

Lower mowing heights
remove more
photosynthetic tissue

Lower mowing heights
require more
frequent mowing

Lower mowing heights
reduce root depth
and health
Mowing Height Affects Weed Seed
Germination and Weed Vigor
Consequences of Poor Irrigation
Coverage on Sports Turf
•
•
•
•
•
Inconsistent wear and recovery
Inconsistent nutrient use
Inconsistent hardness
Inconsistent footing
Increased potential for disease
and weeds
• WHY? CAUSE? Plants unable to
produce sufficient energy to
maintain vigor and growth
Pod 2 – Two weeks later
Mow Frequently…Especially in the Spring
• The “1/3 rule”: avoid
cutting off more than
1/3 of the turf’s height at
any single mowing
• Healthier for the grass
• Fewer pest problems
• Lawn looks nicer after
mowing
Light Quantity AND Quality
The Problem of Shade





Trees reduce the amount of
light
Trees filter out blue-violet
and orange-red wavelengths,
known as Photosynthetically
Active Radiation (PAR)
Tree roots compete for water
and nutrients
Turf remains moist longer in
shade, increasing potential
for disease
C3 grasses tolerate shade
much better than do C4
grasses
Potential Problems with High Light Intensity
ROS = reactive oxygen species (peroxides, free radicals)
Tenacity (mesotrione) on Nimblewill
What is photorespiration?
The Problem of Photorespiration





Photorespiration in C3 plants is favored by
constant high (>80 F) root zone and air
temperatures, long days, bright sunlight, poor air
movement, drought stress
C3 plants close stomates to reduce transpirational
water loss; O2 accumulates (relative to CO2),
reducing efficiency of CO2 fixation
CO2 fixation in C4 leaves occurs in bundle sheath
cells, where O2 concentration is kept low
C3 grasses may be up to 50% less efficient in
CO2 fixation than C4 plants under the same
conditions
Turf plants use more energy than is produced by
photosynthesis




Root decline
Reduced water and nutrient uptake
Reduced disease and insect resistance
Reduced traffic tolerance and recovery
How Are Growing Conditions Different?
Growing C3 Grass in the Arid Southwest




Low humidity allows for
better transpirational
cooling; better exchange
of air in canopy
Cool nights reduce
respiration rates
More favorable energy
balance within the plant
Less disease than in
humid areas
What will we talk about?
• Photosynthesis…why it’s important for the sports turf
manager to understand
• The difference between warm-season and coolseason grasses (and weeds)…and why it matters…for
weed control, fertilization, irrigation, shade tolerance,
and where you plant them?
• What plant hormones are…why they are
important…and how/why we manipulate them for our
benefit?
• Why biostimulants sometimes work…and sometimes
don’t (or it seems that way, anyway)?
mid-October in
Fort Collins
Buffalograss
(C4)
Tall fescue (C3)
Differences Between C3 and C4 Grasses
C3 Grasses






CO2 compensation
concentration 30-70 ppm
Photosynthesis depressed by
oxygen
CO2 released in light
(photorespiration)
Maximum photosynthetic rate
requires ¼ to ½ full sunlight
Net photosynthetic activity is
slight to high
Energy stored as simple
sugars and fructosans
C4 Grasses






CO2 compensation
concentration <10 ppm
Photosynthesis NOT
depressed by oxygen
CO2 NOT released in light (NO
photorespiration)
Maximum photosythetic rate
requires FULL SUNLIGHT
Net photosynthetic activity is
high to very high
Energy stored as starch
Cool-Season (C3) Species
 Bluegrasses, ryegrass, fescues,
bentgrasses are cool-season turf
species
 Dandelion, thistle, bindweed
are cool-season broadleaf
weeds
 Quackgrass, bromegrass, annual
bluegrass are perennial weedy
grasses
 Grow best (and are easiest to
control) during spring and fall
C4 Summer Annual and Perennial Weeds
Annual grasses crabgrass, foxtails,
goosegrass, barnyardgrass
 Annual dicots purslane, spurge
 Perennial grasses bermudagrass,
zoysiagrass, nimblewill, windmillgrass
 Aggressive competitors with C3
grasses during the summer months

C3 vs C4 Differences in Water Use





C3 grasses must leave stomates open
longer than C4 grasses to capture CO2
Open stomates lose more water
C4 grasses use less water per unit of
CO2 fixed (more dry matter production
using less water)
C3 grasses are more easily drought
stressed during warm weather
When C3 grasses CLOSE stomates in
response to drought, photorespiration
becomes a problem (decreased carbon
fixation and dry matter production – as
compared to C4 under the same
conditions)
What is photorespiration?
Transition Zone






Winters may be severe
enough to kill warm-season
grasses
and/or
Summers may be warm
enough to cause problems for
cool-season species
Best grasses for the transition
zone:
turf-type tall fescue
zoysiagrass
buffalograss
cold-hardy bermudagrasses
Nitrogen
•
•
•
•
•
•
•
Chlorophyll
DNA
RNA
ATP
Enzymes
Amino acids
Proteins
Turfgrass Nitrogen Cycle

“Organics”
Grass clippings
Volatilization (NH3)
Urea
Ammonium

Organic
Urea

Soil
Organic
Nitrogen



NH4+
Denitrification
N2 , N2O

Nitrate

Plant
uptake
NO3-


Microbial
uptake

Nitrate Leaching


Clipping Removal
Nitrogen Conversions
 Urea hydrolysis
 Nitrification
 Plant uptake
 Microbial uptake
 Decomposition
 Mineralization
Nitrogen Losses




Nitrate leaching
Denitrification
Volatilization
Clipping removal
Cool Season Turfgrass Root and Shoot Growth
Top growth
Root growth
Root Growth
High Spring N
Winter
Spring
Summer
Autumn
When Should I Fertilize?
Cool-season grasses
 fall
 late spring
 little in summer
Bluegrasses, fescues, ryegrass,
bentgrasses
Commercial Lawn Care
When Should I Fertilize?
Buffalograss lawns!!!
Warm-season grasses
 Late May/June and July
 Avoid late summer & fall
 Early spring fertilization
encourages weeds and
doesn’t promote earlier
green-up
Fertilize once or twice annually
What will we talk about?
• Photosynthesis…why it’s important for the sports
turf manager to understand
• The difference between warm-season and coolseason grasses (and weeds)…and why it
matters…for weed control, fertilization, irrigation,
shade tolerance, and where you plant them?
• What plant hormones are…why they are
important…and how/why we manipulate them
for our benefit?
• Why biostimulants sometimes work…and
sometimes don’t (or it seems that way, anyway)?
Potential Problems with High Light Intensity
ROS = reactive oxygen species (peroxides, free radicals)
Patriot Bermudagrass in West Lafayette, IN
Huang, Rutgers University
Trinexapac-ethyl: Anti-Gibberelin PGR
•
•
•
•
•
•
•
•
•
ArmorTech
Goldwing
Governor (dry)
Groom
Primeraone
Primo Maxx
Provair
T-Nex
T-Pac
Primo/TE Use Questions
I use trinexapac ethyl/Primo:
a. Monthly or more often during the growing
season
b. Maybe 1-2 times annually
c. Very rarely
d. I don’t use TE/Primo
Primo/TE Use Questions
I apply trinexapac ethyl/Primo (approximately):
a. Weekly
b. Every 2 weeks
c. Monthly/every 4 weeks
Primo/TE Use Questions
When I use TE/Primo, I usually use this rate:
a. Less than 0.125 oz/1000 (5.5 oz/acre)
b. 0.25 oz (11 oz/acre)
c. 0.5 oz (22 oz/acre)
d. Not sure
PGR Effects on Sports Turf Quality
• Increased density
(tillering)
• Better overseeding
success
• Enhanced shade
tolerance
• Earlier spring green-up
• Enhanced carbohydrate
status
• Better stress tolerance
Reduced internode length
Trinexapac-ethyl Effects on Turf Quality
TE Suppression Varies with Turf Species
TE Timing…Does the Calendar Work?
Correlation of GDDs with TE Suppression
U. Wisconsin (Soldat) Growing Degree Day
Model for TE/Primo Application
Assumptions
• Model restarts with a Primo application
• Minimum temperature is 0 C (NOT F!), with no
maximum temperature
• Get average daily temperature in degrees C
• Just add average daily temperatures together
• Re-apply TE when you hit 200 GDDs
• Turns out to be about 200 GDDs when using Base
50 F model as well (Average daily F – 50)
How Can the Sports Turf Manager Use the
TE “Rebound Effect”?
Weather Channel GDD Calculator is Easy to
Use…But Doesn’t do Centigrade
Does Height of Cut Affect TE Effectiveness?
Doug Soldat, University of Wisconsin
Primo/TE to Reduce Stress?
• Zeatin riboside is a
cytokinin
• Cytokinins are
important for:
• promoting shoot and
root growth, retarding
senescence
• TE use can
enhance/promote
production of this
cytokinin
What will we talk about?
• Photosynthesis…why it’s important for the sports
turf manager to understand
• The difference between warm-season and coolseason grasses (and weeds)…and why it
matters…for weed control, fertilization, irrigation,
shade tolerance, and where you plant them?
• What plant hormones are…why they are
important…and how/why we manipulate them for
our benefit?
• Why biostimulants sometimes work…and
sometimes don’t (or it seems that way, anyway)?
Does it all…Is that possible?
What is a “biostimulant”?
• an organic material
• applied in small quantities
• enhances plant growth
and development
• the response cannot be
attributed to application
of traditional plant
nutrients
Biostimulants, Phytohormones
•
•
•
•
•
•
•
cytokinins
amino acids
phosphites
silicon
glycoproteins
salicylic acid
Also referred to as
“elicitors”
• Used to be…and still are
called…”snake oils”
Potential Problems with High Light Intensity
ROS = reactive oxygen species (peroxides, free radicals)
Reducing Effects of Summer Decline
• Improve air circulation
(fans)
• Subair
• Syringing (to cool)
• Biostimulants???
How and why does exogenous (i.e., applied) cytokinin work?
• increases the in-plant
(endogenous) natural
production of
antioxidants
• in plants, antioxidants atocopherol (vitamin E)
and ascorbic acid (vitamin
C) are concentrated in the
chloroplast and protect
the photosynthetic
apparatus when a plant is
subjected to stress
• scavenging free radicals
Oh PLEASE catch
it! No…not you…
awww wrong guy!
CSU Turf Program Web Site
http://csuturf.colostate.edu
Diagnosing iron (Fe) deficiency
•
•
•
•
•
Patchy yellowing of turf
Turf may thin
Youngest leaves usually affected
first
Becomes worse with nitrogen
fertilization, high moisture
Promoted by:
–
–
–
–
–
–
Excess N rates
High (>7) soil pH
Very wet or dry soils
Saline soils
Compaction
Any conditions that reduce root
health
– Species and cultivar sensitivities
Foliar nutrients (like urea, iron) are
absorbed into the leaf through:
A.
B.
C.
D.
E.
Nanopores
Stomates
Xylem
Guard cells
The amount of beer I had last night will not
allow me to answer at this time; ask me later
Nutrient Absorption into Nanopores
• Monovalent (K+) easier
than divalent (Fe +2)
• UNCHARGED molecules
(like urea) move easily
• High concentration can
overcome repulsion of
CHARGED molecules
• Uptake is greater when
nutrients are in solution
Spray Solution Effects on Ion Absorption
Concentration
– Increased uptake with
increasing concentration
– High concentration may
injure leaf surface
Surfactant use
– Beneficial in most cases
– Critical in some cases
Solution pH
– Slightly acidic to neutral
is best
Complexing and Chelating Agents for Metal Ions
• Positively charged metal
ions can’t easily enter
nanopores
• Complexing/chelating
results in a neutral to
slightly negative molecule
• Neutral molecule can
move easily through a
nanopore
Organic Complexing and Chelating Agents
•
•
•
•
•
Amino acids
Fulvic acids
Lignosulfonates
Citric acid
Humic acids/humates
Iron amino acid
Complexing and Chelating Agents for Metal Ions
Complexing and Chelating Agents for Metal Ions
Shade Effects on Foliar Nutrient Uptake
• Initial foliar uptake of
nutrients is slowed in
shade
• After 6 hours, shaded turf
is equal to or better than
full sun
• Shaded turf should be
mowed first; delay
irrigation following
application by at least 6
hours
Iron Source Effect on Chlorosis
(Ryan Goss, New Mexico State University)
T HE P ROBLEM WITH S CALPING

Violates the 1/3 rule

Visually unattractive

Kills roots

Increases weed and
disease problems
During the active growing season I apply a
plant growth regulator (like Primo):
A.
B.
C.
D.
Frequently (weekly or every couple of weeks)
Infrequently (monthly or less often)
Hardly ever
Never use PGRs
Trinexapac-ethyl enhances traffic tolerance of
turf by:
A.
B.
C.
D.
Increasing turf water use rate
Increasing tiller density and leaf cell density
Reducing photorespiration
Decreasing root length density
W HAT IS A PGR?

Chemicals used to alter the growth of a plant or
plant part

Hormones are substances naturally produced by
plants

Control normal plant functions


Growth—root and shoot

Fruit set and drop
First used in the 1930s: the first discovery and use of
plant growth regulators was with acetylene and
ethylene, which enhanced flower production in
pineapple
A DVANTAGES
OF
PGR S
ON
T URF

Labor savings—fewer hours mowing

Improved operator safety in hard to mow areas

As an edging tool (fence lines, structures in the
landscape)

Reduce mowing and clippings (up to 50%+ for 4+ weeks,
depending on PGR and use rate)

Improved ball lie on golf course fairways

As a means to increase greens speed without lowering
mowing height

More uniform green speed throughout the day

Reduce scalping during extended rainy periods

Enhanced mowing striping patterns
O THER PGR A DVANTAGES

Less mowing means less wear and
downtime of equipment

Mowing equipment performance is
improved due to less force needed to
cut the turf
P OTENTIAL D ISADVANTAGES
OF U SING PGR S

Turf discoloration

Turf death—products are rate sensitive

Increased disease incidence or severity

Reduced traffic tolerance

Slower recovery from wear/damage

They don’t control weeds

Expensive

Unpredictable turf response

Reversing the effect not always easy