Diapositiva 1

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SAVING WATER IN IRRIGATION CAN IT BE DONE? Elias
Fereres Institute for Sustainable Agriculture
(CSIC) and Univ. of Cordoba, Spain
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IMPROVING THE EFFICIENCY OF WATER USE REQUIRES A
MULTIDICIPLINARY APPROACH, COMBINING SCIENCES AND
ENGINEERING APPLICATIONS
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EFFICIENCY OF WATER USE IS OFTEN LIMITED BY
FACTORS OTHER THAN WATER,
RAINFED
IMPROVING MANAGEMENT AT ALL LEVELS IS MOST
CRITICAL
Sadras Angus
Gonzalez Mateos
IRRIGATED
IRRIGATED
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MODERNIZATION/REHABILITATION NEW
INFRASTRUCTURES vs. IMPROVED MANAGEMENT
(flexibility of operation, multi-year storage,
water pricing, etc..)
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Uniformity of water application
Photo Courtesy Dr. D. Goldhamer, UCDavis
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Efficiency and the critical role of uniformity of
water distribution The need for assessing
irrigation performance
THE EFFICIENCY PATH IS TO GO FROM CURVE A TO C,
NOT TO B
C
TARGET WATER DEPTH
Fereres Gonzalez
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EFFECTS OF IRRIGATION UNIFORMITY ON THE RELATION
BETWEEN YIELD AND IRRIGATION WATER
As uniformity decreases, more water is needed to
achieve high yields
Fereres et al., 1993, ICSC, Ames, Iowa.
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Options available
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Under Water scarcity, Reduce Water Consumption
(ET)
Therefore decrease
E and/or T
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DEFICIT IRRIGATION APPLICATIONS BELOW CROP
WATER REQUIREMENTS (ET) (Soil water deficits may
or may not cause crop water deficits and
reduction in ET) REGULATED DEFICIT IRRIGATION
(RDI) PLANNED CROP WATER DEFICITS AT SPECIFIC
DEVELOPMENTAL STAGES. (Crop water stress occurs
at certain stages ET may or may not be reduced
significantly RISKS increased)
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Pistachio Nut Development
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Five-year peach experiment in Cordoba, where RDI
and SDI were compared to full irrigation in both
DI treatments, 66 of the full was applied
Soriano Fereres
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Sometimes RDI may not be the best strategy
Almond yields (kg/ha)
APPLIED WATER mm
Goldhamer et al., 2006
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Mature Navel Oranges San Joaquin Valley 3
Season Mean
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Mature Navel Oranges San Joaquin Valley 3
Season Mean
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RDI experiment in Pistachio in Madera Co.,
Calif., where ET was measured with different
methods, to assess the true water savings of RDI.
Iniesta et al., 2008
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COTTON YIELD RESPONSE TO WATER IN SOUTHERN
SPAIN The yield-response function was generated
for wet (R), normal (N), and dry (D) years, using
a computer simulation model.
Garcia-Vila et al
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AquaCrop a simulation model of water-limited
crop production, currently being developed in FAO
by P. Steduto et al.,
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FARM INCOME AS A FUNCTION OF APPLIED WATER AND
WATER COSTS Cotton gross income in Southern Spain
under current CAP of the EU
Water costs
Yield threshold for EC subsidy (2600 kg/ha)
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Spain, RDI strategy
Profits (/ha)
MODERATE RESTRICTIONS (60 of FI)
Water Allocation 3000m3/ha (1ac/ft)
Income (FI) (/ha) Maize 919.3 Cotton 813.0 Whe
at 520.1
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Agua consumida / Agua requerida
ASSESSING IRRIGATION PERFORMANCE
Relative Irrigation Supply
(Lorite et al., Irrig.Sci., 2004)
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Satellite-based estimation of consumptive use
(ET) for planning and for performance
assessment. (SEBAL, METRIC, etc.,)
Large variations in Crop ET among farms
Lorite et al., 2007
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Limitations of satellite imagery Time interval
(every 14 days), problems with thermal sensors,
pixel size, etc..
Goal monitoring irrigation management
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Citrus San Joaquin Valley
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What indicator of stress??
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Problems with point observations the spatial
variability
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THE Crop Water Stress Index, (CWSI) ALSO WORKS
ON TREES!
Testi et al., 2008
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Maize
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Flights over a field of 30 maize cultivars
replicated three times, showing images of canopy
temperature diferential where variations among
cultivars are detected prior to irrigation
L. Suarez et al.,
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Stomatal conductance and canopy temperatures of
two maize cultivars
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Another stress indicator based on reflectance PRI
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WORKS AT THE CANOPY LEVEL AS WELL
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Suarez et al., submitted
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