irrigation of wine grapes
TRANSCRIPT
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Regulated Deficit Irrigation of Quality Wine Grapes«
By Praveen J. GaikwadViticulturist and Consultant
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Vine Use (Water use)
Water Supply :
Irrigation
In season Rain
Soil Stored Water
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Soil Water Reservoir
Soil water holding capacity:
Soil Texture
Soil Structure
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Root Zone Depth
Root limiting conditions Rootstock performance
Previous irrigation cycles
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Quality Improvement Ideas:
Crop load management (thinning)
Canopy Management (leaf removal) Crop selection (Drop)
Water deficit (Timing and severity)
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Benefits of Irrigation Scheduling:
Reduced costs (Energy and water)
Control of Excess Vegetative Growth Reduced cost of leaf removal
Reduced disease
Increased fruit quality Reduced environmental risks
Reduced fertilizer losses (deep percolation)
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Irrigation management philosophy:
Controlled water deficits can improve fruit
quality with little effect on yield.
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Irrigation of quality wine grapes
Determine : when to begin , how much to
apply. Achieve predictable response
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Effect of water supply on Vine:
Beneficial and harmful depending on timing
and severity. Moderate Deficit- close stomata to limit water
loss. Reduction in vegetative growth.
Longer deficit- limited photosynthesis and
production of sugar.
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Measuring Soil Moisture
Soil Probe / soil sampling
Tensiometers Electric resistance blocks
Neutron Probes
Dielectric soil moisture sensors
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Deficit Irrigation
Vegetative Growth ± can reduce
Improved color ± can increase Juice characteristics- can increase
Yield ± may reduce
Water volume costs ± will reduce
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Timing of water deficits:
Early season deficit (Pruning time) ±
uncommon, because high moisture in soil,low demand by plant.
Midseason deficit ± possible in low rainfall
areas
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Veraison to harvest irrigation
Excess supply: growth of lateral shoot-
competitive sink for photosynthate, delay infruit maturity.
Full Water potential: reduced wine colour.
Severe deficit: senescence of lower, interior
leaves, reduced sugar accumulation.
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Deficit from veraison to harvest:
Moderate deficit: slightly smaller berries with
more color, character, sugar. White varieties maximum yield at moderate
deficit :60-70 % Full water potential.
Reds decrease yield but improve character
and color. Increased rate of sugar
accumulation, early harvest.
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Deficit Threshold Irrigation:
Decide the threshold- predetermined level of
midday water deficit ± to begin irrigation. Goal ± improve fruit quality and minimize
yield reduction.
Shoot length
Shoot tip condition
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Midday leaf water potential
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To be continued«
Next :
Selecting appropriate deficit threshold.Selecting post threshold RDI %
Estimating Full Potential Water use byEvapotranspiration ref values, Crop
Coefficient. ETo X Kc = FPW (ETc)Calculating amount of water to apply using DTI
/ RDI
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Net Irrigation requirement =
Full Potential Water use X 60% RDI ± Effective
In season Rainfall ± Soil Contribution.