crop water management
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Water managementWater management
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EvapoEvapo--transpiration (definitions)transpiration (definitions)a) Evaporation: The process by which wateris changed from the liquidor solid state into the gaseous state.
b) Transpiration: The evaporation of water that pass throughplant
tissue.
c) Evapo-transpiration, ET: It is the sum of the amount of watertranspired by plants and that amount that is evaporated from soil.
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Evapo-transpiration
Transpiration
Evaporation
Rain
Runoff
Drainage
Root Zone Water Storage
Irrigation
Below Root
Zone
Water budgetWater budget
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Water BudgetWater Budget
Input
o Rainfall
o Irrigation
Outputo Transpiration
o Evaporation
o Runoff
o Drainage
Water StorageWater Storage
oo SoilSoil
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Water budgetWater budget
)(
)-(evapo)(
drainagerunoff
iontranspiratirrigationrainstorageSoil
!
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Water management principlesWater management principles
How much water to apply?
When to irrigate?
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How much?How much?
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Weighing lysimeterWeighing lysimeter
Direct estimate and precise of water supplyDirect estimate and precise of water supply
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Ideal SituationIdeal Situation
Soil water balance
drainage
Water supply
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LysimetersLysimeters Direct measurement ofDirect measurement of
EvapoEvapo--TranspirationTranspiration
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M
easu
ring Crop ETM
easu
ring Crop ETInside view of weighing
lysimeter
3 m1995 Soybean
Crop
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How much water is require?How much water is require?
Direct Estimate:
o lysimeters
Indirect estimate: (ET0).
o Climate: Penman monteith
o Class A pan.
o Crop Standard Water loss by grass (tall fescue) 8 15in height. (direct measurement by a Lysimeter).
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Direct Estimate: EvapoDirect Estimate: Evapo--transpiration (ETtranspiration (ET00))
Evapo-transpiration from Crop Standard.
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LysimeterLysimeter
Implementation in the field
Water loss and climate
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Indirect estimate:Indirect estimate:
Penman monteith Class A Pan
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Estimating Crop Water RequirementEstimating Crop Water Requirement
Crop water requirement can be estimatedfrom Class-AEvaporation Pan.
Size:Diameter - 120.7 cmDepth - 25 cm
Location: on a palette, in an open fieldsurrounded by short green grass.
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Class A PanClass A Pan
unpainted galvanized iron
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Types of Evaporation PansTypes of Evaporation Pans
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A Comparison of Standard Open PansA Comparison of Standard Open Pans
Pan Dimensions Pan Coeff icient
US Class A 1.2 m Diameter; 250 mmDeep
0.7 (0.6 to 0.8)
Australian Pan 900 mm Diameter; 900
mm Deep. Large Pan:
1200 mm Diameter and850 mm Deep
0.9 ( 0.6 to 1.2)
BritishTank 1.83 m Square 0.9 (Very Variable)
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Climate: PenmanClimate: Penman--Monteith EquationMonteith Equation
Combination Approach
? Aastapan
rr
recGRE
(
(!
1
/)(
KP
HV
Net Radiation Mass Transfer
Slope of
Sat-vp curvePsychrometric
Constant
density, specific heat
of air
Canopy, atmospheric resistance
Brooks et al., eq. 3.23
VPD
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PotentialPotential EvapoEvapo--transpiration (ETtranspiration (ET00))
Equations like Penmans assume that the vegetated surface iswet enough to be freely evaporating without biotically imposedrestriction. For this condition ETis the Potential
Evapotranspiration (ET0
).
Dozier, 2003
ET0 = amount of water transpired in a unit time by ashort green crop, completely shading the ground surface,ofuniform height, and never short of water(Penman,1948)
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Factors that affect actual ETFactors that affect actual ET
Weather parameters
Crop Characteristics
Management andE
nvironmental
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Weather ParametersWeather Parameters
Radiation
Air temperature
Humidity
Wind speed
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Crop factorsCrop factors
Crop Type
o Variety of Crop
Plant density
o Ground Cover
Development Stage
Crop Height
Crop Rooting Depth
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Management and Environmental FactorsManagement and Environmental Factors
Soil type
o Land fertility
Soil salinity
Waterquality (salinity) Plant health
o Disease and pest management
Type irrigation system.
o Water management (frequency of water supplyand ct.)
oo IrrigationIrrigation efficiencyefficiency
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Crop waterrequirement
2
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EvapoEvapo--transpiration and Croptranspiration and CropCoefficientCoefficient
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ETccrop Evapo-Transpiration
Penman referent cro ETo
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TranspirationTranspiration is related to the plant sizeis related to the plant size
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The transpiration change according theThe transpiration change according theplant size and stageplant size and stage
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Crop coefficients, KCrop coefficients, Kcc
)RHmin 45%, u2 2 m/s foruse with the FAO Penman-MonteithETo
Kce d
M ximum Cr
Heigh (h) (m)
1.05 0.95 0.4
1.05 0.95 0.3
-y
1.05 0.75 0.4
- g ee 1 1 0.3
- see 1.05 0.8 0.5
1.05 0.75 0.4
0.4 1 0.75 0.4
0.5 1.1 0.95
Cr
Sweet el sW te mel
O i s
C bb ge
C ts
. R ts
ube s
Kci i Kcmid
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0 0.05 0.1 0.2 0.4 0.7 0.9 1 0.8Kc
Sorghum crop coefficient
Booting heading soft/hard dough
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0 0.05 0.1 0.2 0.4 0.7 0.9 1 0.8Kc
Sorghum crop coefficient
Penman evaporation (example) and waterrequirement of sorghum
ETo mm/day 5.7 5.7 5.7 5.7 5.5 5.4 5.3 4.0
ETc mm/day 0.3 .6 1.2 2.3 3.85 4.9 5.3 3.2
1mm=10m3/ha
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0.1 0.3 0.5 0.8 0.9 1.1 0.8 Kc
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3- to adapt the variety (early med.- late)
Early variety
med. variety late varietylate variety
Kc
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Skipping row
Between rowsand inside
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3- to adapt the no. planted rows
skipping 2 rows
Skipping 1 rowFull rowsFull rows
Kc
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1 m
25 cm12.5cm
1 m
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Skipping2 rows
Skipping 1row
Fullplanting
4 plants/m 20.000 26400 40.000
5 plants/m 25.000 33.000 50.000
6 plants/m 30.000 40.000 60.000
7 plants/m 35.000 46.200 70.000
8 plants/m 40.000 53.000 80.000
Plant stand /ha
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0 0.05 0.1 0.2 0.4 0.7 0.9 1 0.8Kc
Sorghum Water management
ET0 mm/day 5.7 5.7 5.7 5.7 5.5 5.4 5.3 4.0ETc mm/day 0.3 .6 1.2 2.3 3.85 4.9 5.3 3.2
ETc mm/phase 2.4 6 12 46 96 98 79.5 48
no.days 8 10 10 20 25 20 15 15
ETc m3/phase 24 60 120 460 960 980 795 4804800 m3/ha
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Soil Available water(Storage)
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What is soil?What is soil?
Mineral and organic material that serves as anatural medium for the growth of the plants.
Kind of bio-filter:
o Recycling system for nutrients, wastes...
o Water purification.
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Soil made ofSoil made of
Inorganic component
o Called minerals
o They come fromweathering of bedrock
or and material that iswashed or blown in.
Organic component
o This comes from material
living in or on the soil.
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Soils originating from differentSoils originating from differentparent materialsparent materials
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, :
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--
:
o
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Soil provideSoil provide
Physical support - Anchorage
Water supply
Mineral (nutrients) supply
Media for negative andpositive micro-organism
deep percolation
appilary rise
round ater
H
Transpiration
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Soil main propertiesSoil main properties
WaterHolding Capacity (permeability)
Nutrient-Holding Capacity
Aeration ( porosity)
pH
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Four Principal Components of SoilFour Principal Components of Soil
rganic
5%
Water25%
Mineral
45%
ir
25%
ir Water Mineral rganic
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Particles composition of soil mineralParticles composition of soil mineral
FINE SAND
SILT ..CLAY
Relative size of : Sand, Silt andClay
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Particle diameterParticle diameter
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The proportionate quantity of sand, silt and clay inthe mineral fraction of a soil.
There are 12 textural classes which can be seen in
the next slide.
Soil TextureSoil Texture
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Soil water statusSoil water status
Soil saturated - all pores are water-filled.
Field Capacity - the most loosely heldwaterin the largest pores drained out.
Wilting point - only the smallest porescontain water
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Soil water statusSoil water status
SaturatedSaturated: Soil water potential is 0 bar
F.C.:F.C.: Soil water potential is 1/3 bar
WiltingWilting: Soil water potential is 15 bar
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Analyze soil water potentialAnalyze soil water potential
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Pressure plate methodfor potentials from1 bar to 15 bars
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Available water in soilAvailable water in soil
-(-0.3m)
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Effect of soil texture on waterEffect of soil texture on water
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Soil water storage in every cm in depthSoil water storage in every cm in depth
% Fiel
capacit
% Wiling
point
% Total water
available
mm o water
availableinevery
cm
mm of water
to 1m depth
and 8 4 4 0.4 40
Sandyloam 18 7 11 1.1 110Laom 28 12 16 1.6 160
Siltloam 34 15 19 1.9 190
Clayloam 36 17 19 1.9 190
Clay 38 21 17 1.7 170
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Root DepthRoot Depth
Crop Depth (m)
Banana 0.6
Citrus 1.2
Corn 0.8
Tomato 1.2
Cotton 1.5
Melon 1.2
Root depth and soil water depletionRoot depth and soil water depletion
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Root depth and soil water depletionRoot depth and soil water depletionfraction for no stress (p)fraction for no stress (p)
Ma i u oot
De th 1De etion Fraction
2
orE } ay)
( ) p
0.4-0.6 0.45
0.4-0.6 0.45
0. -0.8 0.45
0. -1.0 0.35
0.4-0.7 0.45
0.3-0.5 0.2
0.3-0.5 0.3
0.3-0.5 0.3
Garlic
ettuce
Cabbage
Carrots
Cauli lo er
Celery
Crop
a. Small egetables
Broccoli
BrusselSprouts
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Irrigation rate of sprinklerIrrigation rate of sprinkler
The precipitation of a spr inkler irrigation system(Pr) is the rainfall rate of the spr inkler water
supply.
q - sprinkler rate in l/hS - Spacing between the sprinklerin m
wl ss
q
!Pr
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Precipitation RatePrecipitation Rate
wl ss
q
!Pr
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ExampleExample -- sprinklersprinkler
sprinkler one nozzle 4.5 mm pressure - 2.5atmosphere
q - 1,290 l/h (1.29 m3/h),s - 12 x 9 m (108 m2),
hmmhmm/12/94.11108
290,1P
r!!