mark greenspan, ph.d., cpag, cca advanced viticulture, … - irrigation... · sap flow,...
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Mark Greenspan, Ph.D., CPAg, CCAAdvanced Viticulture, Inc.
www.AdvancedVit.com
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To discuss a simple irrigation
management scheme
• based on continuous soil moisture
measurements
• focusing on soil moisture dynamics
• in conjunction with plant moisture status
Water conservation
• high vine WUE
• precise, efficient irrigation
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Allow vines to deplete rain-fed soil moisture to encourage deep and extensive rooting
Impose mild stress on vines to put them in a state of high water use efficiency
Monitor vine stress to create sufficient stress, but not excessive stress
Use soil moisture monitoring to precisely apply irrigation.
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• Identify effective root
zone
• Track rainfed moisture
depletion
• Determine actual
depth of irrigations
• Indicate onset of vine
stress
• Determine exactly
how long irrigations
take to become
depleted
• Precisely irrigate
Plant moisture
• How does vine
respond to soil
moisture content?
• Identify water-use
efficient state/range
• Avoid excessive vine
stress
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Monitoring is “feedback” used to adjust
irrigation schedule
Methods include:• Visual Indicators – shoot elongation rates, shoot
tips, droopy tendrils, leaf sun-avoidance, basal
leaf senscence
• Plant water status instruments:
Pressure Chamber
Porometer
Sap flow, dendrometry, surface renewal
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Rapid Growth Slowing Growth Almost Stopped Stopped Dead Tip
5 4 3 2 1
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Pressure Chamber
Porometer
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Pressure chamber• Measures “suction” in the xylem vessels• Advantages: Portability; repeatability; ruggedness• Disadvantages: No indication of vine physiological response; reading depends
on time since last irrigation, grape variety, daytime conditions, etc.
Measurement can be misleading on its own
• IMPORTANT: Place leaves in plastic bags immediately before removal and during measurement
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omPorometer
• Measures stomatal conductance (facility of pores to transpire water)
• Advantages: Portability; vine response to water status; indirect indication of photosynthesis
• Disadvantages: More delicate instrument; sensitive to environmental conditions; more variability than leaf water potential measurements
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What are stomata?
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Suzy Y. Rogiers*, Dennis H. Greer, Ron J. Hutton and Joe J. Landsberg
Journal of Experimental Botany, Vol. 60, No. 13, pp. 3751–3763, 2009
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Porometer/Stomatal Conductance - Units are in mmol/m2/s
450 400 350 300 250 200 150 100 50 0500
“Luxury” Mid-Range Mod.
Stress
Stress Extreme
Stress
Slight
Stress
9 10 11 12 13 14 15 16 17 188
“Luxury” Mid-Range
Mod.
Stress Stress
Extreme
Stress
Slight
StressShoot stopping
Pressure Chamber/Leaf Water Potential (-bars)
High WUE
Range
Red target White target
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Measure at multiple levels to determine
depth of irrigation
Measure continuously
Use to determine nominal irrigation volume
per application
Use to determine nominal irrigation
interval between applications
Use in conjunction with plant moisture
status measurements to precisely adjust
intervals per changing weather conditions
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Soil matric
potential sensors
Soil water content sensors &
probes
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20
Relative permittivity
of water is
About 80x that of air
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Stair-steps
indicate
day/night water
pattern
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Upper
limit of
RAW
Lower
limit of
RAW
Set a reference
volume for
refill point
Progressive
stress reflected
in slope
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ETo = 4.42”
Kc = 0.5
ETc = 2.21”= 66 gal/vine
Actual Irrigation: 12 gallons/vine
18% of Etc
Possible IF vines are in high WUE range
Cab. Sauv, 8’ x 6’ spacing, south Napa
County, 3rd leaf
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Vin
e W
ate
r S
tress
Budbreak Bloom & Fruit Set
Veraison Maturity
“Magic Window”
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About 2 weeks prior to veraison and
through complete veraison
Achieving moderate stress:• Reduces and stops vegetative growth
• Puts vines in high water use efficiency range
(important for low irrigation volumes)
• Stimulates production of ripening enzymes in fruit
• Most effective in red varieties
• Allows for flavor ripeness at lower brix
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Soil Moisture
• Measure continuously, and at several depths
• Use multi-level to determine proper volume, THEN
• Use to sum/average graph to determine intervals as
season progresses
• Irrigation scheduling adjusted to soil characteristics
using these tools
Plant moisture status
• Measure to track stress and adjust refill point and
irrigation intervals as needed
Mark Greenspan, Ph.D.Advanced Viticulture, Inc.
Windsor, California707-838-3805
Web: www.AdvancedVit.comEmail: [email protected]