usda-ars crop et pet networks how to obtain & use information from the internet crop et pet...
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USDA-ARSUSDA-ARS
• Crop ET
• PET Networks
• How to obtain & use information from the internet
• Crop ET
• PET Networks
• How to obtain & use information from the internet
Irrigation TechnicalTraining
Irrigation TechnicalTraining
Texas SWCSKerrville, TexasJune 16, 1999
Texas SWCSKerrville, TexasJune 16, 1999
IRRIGATIONSCHEDULINGIRRIGATION
SCHEDULING
Irrigation SchedulingIrrigation
Scheduling• Soil water balance
– soil / plant / atmosphere / water
• Irrigation system dynamics– efficiency / uniformity
• Metering (control & feedback)– irrigation water / soil water / crop water
• Soil water balance– soil / plant / atmosphere / water
• Irrigation system dynamics– efficiency / uniformity
• Metering (control & feedback)– irrigation water / soil water / crop water
Crop ETCrop ETSoil Water Balance
Si = Si-1 + (P - Q) + (I - Q) - D - ET
Si = “root zone” soil water on day i
(P - Q) = “effective” precipitation
(I - Q) = “effective” (net) irrigation
D = percolation beneath the root zone
ET = evaporation plus transpiration
Soil Water Balance
Si = Si-1 + (P - Q) + (I - Q) - D - ET
Si = “root zone” soil water on day i
(P - Q) = “effective” precipitation
(I - Q) = “effective” (net) irrigation
D = percolation beneath the root zone
ET = evaporation plus transpiration
Soil Water Balance
use inputs losses
ET = SW + (I + P) - (D + Q)
Some percolation (D) may be required for salinity leaching but can contain nutrients and agro-chemicals that are not desirable for the environment.
Soil Water Balance
use inputs losses
ET = SW + (I + P) - (D + Q)
Some percolation (D) may be required for salinity leaching but can contain nutrients and agro-chemicals that are not desirable for the environment.
Crop ETCrop ET
Soil WaterSoil Water• Spatial variability
– crop– soil chemical properties
• salinity• fertility
– soil physical properties• infiltration & percolation• plant available soil water
• Spatial variability– crop– soil chemical properties
• salinity• fertility
– soil physical properties• infiltration & percolation• plant available soil water
Soil WaterSoil Water• Spatial variability (cont.)
– precipitation• runoff & run-on
– irrigation• runoff & run-on• hydraulics / operation dynamics
• Spatial variability (cont.)– precipitation
• runoff & run-on
– irrigation• runoff & run-on• hydraulics / operation dynamics
EvapotranspirationEvapotranspiration
• ET = E + TE = evaporation
T = transpiration
E can depend on irrigation method and wetting frequency
T is strongly correlated to crop dry matter
• ET = E + TE = evaporation
T = transpiration
E can depend on irrigation method and wetting frequency
T is strongly correlated to crop dry matter
Maximum ET Maximum ET
• Potential Evapotranspiration (PET)– basically goes back to Penman (1948)
– not in “vogue” today, except in Texas
– implies zero “bulk” surface resistance• wet crop• water surfaces
• Potential Evapotranspiration (PET)– basically goes back to Penman (1948)
– not in “vogue” today, except in Texas
– implies zero “bulk” surface resistance• wet crop• water surfaces
Reference Evapotranspiration
Reference Evapotranspiration
• Applies to a specific crop– short grass (0.08 to 0.15 m tall; usually a cool-
season type species like fescue, ryegrass, or bluegrass that doesn’t grow in most parts of Texas) … ETo
– tall (>0.5 m tall) alfalfa (again, not a major crop in Texas) … ETr
– well-watered (not deficient in soil water)
• Applies to a specific crop– short grass (0.08 to 0.15 m tall; usually a cool-
season type species like fescue, ryegrass, or bluegrass that doesn’t grow in most parts of Texas) … ETo
– tall (>0.5 m tall) alfalfa (again, not a major crop in Texas) … ETr
– well-watered (not deficient in soil water)
Penman EquationPenman Equation
Wf = 6.43 (1 + 0.53 u2) … for short grasssource Penman (1948)
(Rn - G) + Wf (es - ea)ETo =
( + )
ParametersParameters
= des/T = f (air temperature)
[e*(T0) - e*(Ta)] / (T0 - Ta)
(barometric pressure or elevation)
• (es - ea) = VPD = [es(Ta)] (1 - RH)
= des/T = f (air temperature)
[e*(T0) - e*(Ta)] / (T0 - Ta)
(barometric pressure or elevation)
• (es - ea) = VPD = [es(Ta)] (1 - RH)
Modified Penman Equation
Modified Penman Equation
• the wind function (Wf) is “fitted”• may vary on how VPD is computed• might apply to grass or alfalfa base
depending on Rn and Wf
e.g., FAO-24 Penman equation for grass
• the wind function (Wf) is “fitted”• may vary on how VPD is computed• might apply to grass or alfalfa base
depending on Rn and Wf
e.g., FAO-24 Penman equation for grass
Penman-Monteith Equation
Penman-Monteith Equation
• source Monteith (1965)
rs = “bulk” surface resistance
.... 70 s/m for grass
.... 45 s/m for alfalfa
ra = aerodynamic resistance K / u2
• source Monteith (1965)
rs = “bulk” surface resistance
.... 70 s/m for grass
.... 45 s/m for alfalfa
ra = aerodynamic resistance K / u2
(Rn - G) + 86.4 Cp (es - ea) / raETo = [ + (1 + rs/ra)
FAO-56 PM Equation
FAO-56 PM Equation
• source Allen et al. (1998)
a slight simplification of the Penman-
Monteith equation.
• source Allen et al. (1998)
a slight simplification of the Penman-
Monteith equation.
0.408 (Rn - G) + u2 (es - ea)
ETo = + (1 + 0.34 u2)
900
T + 273
Important ResourcesImportant Resources
19901993 1998
PETPET
• Most often in Texas, due to prior history and use, PET (potential evapotranspiration) is computed for a “grass reference” crop assuming many if not all the concepts in ASCE Manual No. 70, SCS (NRCS) Chapter 2, TWDB-98, or FAO-56.
• Most often in Texas, due to prior history and use, PET (potential evapotranspiration) is computed for a “grass reference” crop assuming many if not all the concepts in ASCE Manual No. 70, SCS (NRCS) Chapter 2, TWDB-98, or FAO-56.
Crop CoefficientsCrop Coefficients
• Single Kc approach
ETc = Kco ETo (grass) or
ETc = Kcr ETr (alfalfa)
The “interchangeability” of Kc values
depends on the ETo / ETr ratio or
function.
• Single Kc approach
ETc = Kco ETo (grass) or
ETc = Kcr ETr (alfalfa)
The “interchangeability” of Kc values
depends on the ETo / ETr ratio or
function.
Crop CoefficientsCrop Coefficients
• Dual crop coefficient approach
ETc = (Kcbo + Ke) ETo
ETc = (Kcbr + Ke) ETr
Kcbo or cbr = “basal” Kco or cr (“dry” soil surface BUT “well-watered” crop )
Ke = soil water evaporation coefficient
• Dual crop coefficient approach
ETc = (Kcbo + Ke) ETo
ETc = (Kcbr + Ke) ETr
Kcbo or cbr = “basal” Kco or cr (“dry” soil surface BUT “well-watered” crop )
Ke = soil water evaporation coefficient
Deficit Soil WaterDeficit Soil Water
• Single Kc approach
ETcadj = (Ks Kco) ETo
ETcadj = (Ks Kcr) ETr
• Dual Kc approach
ETcadj = (Ks Kcbo + Ke) ETo
ETcadj = (Ks Kcbr + Ke) ETr
• Single Kc approach
ETcadj = (Ks Kco) ETo
ETcadj = (Ks Kcr) ETr
• Dual Kc approach
ETcadj = (Ks Kcbo + Ke) ETo
ETcadj = (Ks Kcbr + Ke) ETr
PET NetworksPET Networks
• Provide “uniform” regional coverage with data to guide irrigation decision making
• Educate irrigators and the public about irrigation water needs
• Regional climate and weather data resource
• Provide “uniform” regional coverage with data to guide irrigation decision making
• Educate irrigators and the public about irrigation water needs
• Regional climate and weather data resource
OklahomaMesonet
TexasMesonet
TxPET NetworkSouth Plains (Lubbock)North Plains (Amarillo)TAMU Network (CS)[ Coastal Bend (CC) ]
NP-PET Sites
- PET Sites
> 1,200 mi. for a circuit trip
FarwellDimmitt
Earth
BushlandWhite DeerWellington
DalhartEtter
MorsePerryton
Grass ET Measurement
Grass ET Measurement
• Weighing lysimeter
• 5 ft by 5 ft by 8 ft deep
• Pullman clay loam monolith
• SDI irrigated
• Weighing lysimeter
• 5 ft by 5 ft by 8 ft deep
• Pullman clay loam monolith
• SDI irrigated
Lysimeter ET, mm d-10 2 4 6 8 10 12 14
Co
mp
ute
d E
To
, mm
d-1
0
2
4
6
8
10
12
14
161995199619971998Regression1:1 Line
April throughOctober
ETo = 1.16 + 0.85*ETlys
r2 = 0.728
Measuring Crop ETMeasuring Crop ETInside view of weighinglysimeter
3 m1995 SoybeanCrop
0
2
4
6
8
10
12
14
16
18 S
oyb
ean
ET, m
m/d
0
100
200
300
400
500
600
700
800
Cu
mu
lati
ve E
T, m
m
120 140 160 180 200 220 240 260 280 Day of Year - 1995
1995 Soybean ET
MeanSW LysimeterNW Lysimeter
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
Mean
Kc (
ET
/ P
ET
)
05/01 05/31 06/30 07/30 08/29 09/28 10/28 Date 1995
Mean Kc Kc Reg (n5)
Soybean Crop Coefficient
Pl Em v2 v3 v4 v5 r2 r3 r4 r5 r6 r7 Pm Hv
Crop InformationCrop Information• Crops
– corn, sorghum, wheat, cotton, soybean, peanut
• Sowing Dates– 4 dates that bracket typical practices
• Hybrids / Varieties / Cultivars– full-season and short-season for
sorghum and corn
• Crops– corn, sorghum, wheat, cotton, soybean,
peanut
• Sowing Dates– 4 dates that bracket typical practices
• Hybrids / Varieties / Cultivars– full-season and short-season for
sorghum and corn
NP-PET InformationNP-PET Information
• “Well-watered” crops
• “Normal” crops without diseases or pest problems
• Daily, 3-day, 7-day, seasonal ET rates
• Predicted crop development stage for each crop (& hybrid type) and sowing date
• “Well-watered” crops
• “Normal” crops without diseases or pest problems
• Daily, 3-day, 7-day, seasonal ET rates
• Predicted crop development stage for each crop (& hybrid type) and sowing date
NP-PET Information ...
NP-PET Information ...
• Daily GDDs and GDD sums for each crop (& hybrid type) and sowing date
• 3-day climate summary– rainfall, air temperature, soil
temperatures, and PET
• Alerts and messages (regional pest information, news, upcoming events)
• Daily GDDs and GDD sums for each crop (& hybrid type) and sowing date
• 3-day climate summary– rainfall, air temperature, soil
temperatures, and PET
• Alerts and messages (regional pest information, news, upcoming events)
NP-PET UsersNP-PET Users• Growers / Irrigators / Farm Managers• Production Consultants & Advisors• Agricultural Industries• Agronomists / Agricultural Engineers• Researchers• Extension Personnel• Water District & Regulatory Personnel• Design Personnel & Consultants• Meteorologists / Climatologists
• Growers / Irrigators / Farm Managers• Production Consultants & Advisors• Agricultural Industries• Agronomists / Agricultural Engineers• Researchers• Extension Personnel• Water District & Regulatory Personnel• Design Personnel & Consultants• Meteorologists / Climatologists
NP-PET GoalsNP-PET Goals
• Provide accessible “generalized” data of consistent quality and reliability
• Provide wide-area data for private consultants and crop advisors in near “real-time” so that tailored client products can be developed
• Provide accessible “generalized” data of consistent quality and reliability
• Provide wide-area data for private consultants and crop advisors in near “real-time” so that tailored client products can be developed
How is the NP-PET Information
Disseminated ?
How is the NP-PET Information
Disseminated ?• Daily fax to subscribers (350+ per night)
• Internet Web site
• Daily fax to subscribers (350+ per night)
• Internet Web site
Fax RecipientsFax Recipients
• Subscribed Growers / Irrigators
• Crop Consultants
• Local Cooperatives
• Newspapers
• News Stations: Radio & TV
• Subscribed Growers / Irrigators
• Crop Consultants
• Local Cooperatives
• Newspapers
• News Stations: Radio & TV
WWW UsersWWW Users
• Production Personnel - (own models)
• Consultants - (own models)
• Researchers / Modelers - (water, insect, disease, air, dust modeling development)
• Extension Personnel
• Texas Mesonet (possibility ??)
• Production Personnel - (own models)
• Consultants - (own models)
• Researchers / Modelers - (water, insect, disease, air, dust modeling development)
• Extension Personnel
• Texas Mesonet (possibility ??)
Grass ET EstimatesGrass ET Estimates
• PET data are useful for estimating urban lawn water needs– TAEX Master Gardener Program
– Water Smart Program
• Municipal / Schools / Golf Course irrigation decisions
• PET data are useful for estimating urban lawn water needs– TAEX Master Gardener Program
– Water Smart Program
• Municipal / Schools / Golf Course irrigation decisions
Fax Output of 09/08/96, Etter,TX - (upper left)
Fax Output of 09/08/96, Etter,TX - (upper left)
North Plains PET Network Weather Station, Etter, TX
TemperaturesDate PET ---AIR--- ---Soil-- Prec.
in. Max Min 2 in 6 in in09/05/96 0.20 84 61 70 71 0.0009/06/96 0.18 84 62 69 70 0.1909/07/96 0.13 77 61 68 69 0.03Ten Day Average 69 70
CORN Short Season VarietySeed Acc Grwth Day 3 day 7 day SeasDate GDD Stage -----in/day----- in.
04/01 3148 Harvest 0.00 0.00 0.00 29.504/15 3004 Harvest 0.00 0.00 0.00 28.005/01 2810 Blk lyr 0.09 0.12 0.13 26.305/15 2566 ½ mat 0.12 0.15 0.17 23.4
Fax Output of
09/08/1996- Etter, TX - (upper right)
Fax Output of
09/08/1996- Etter, TX - (upper right)
North Plains PET Network Weather Station, Etter, TX
Date -----Growing Degree Days-----Crn Srg Pnt Cot Soy Bet Wheat
09/05/96 22 22 17 12 26 32 3809/06/96 23 23 18 13 27 33 3909/07/96 19 19 14 9 23 29 37
CORN Long Season VarietySeed Grwth Day 3 day 7 day Seas.Date Stage -----in/day----- in.
04/01 Harvest 0.00 0.00 0.00 32.204/15 Harvest 0.00 0.09 0.14 30.805/01 Blk lyr 0.12 0.16 0.18 27.805/15 ½ mat 0.16 0.20 0.22 24.2
How do you use the information ?
How do you use the information ?
• Rainfall data– field basis
• Irrigation data– field applications
• Rainfall data– field basis
• Irrigation data– field applications
Requires training, requires experience, and requires some local data (rainfall, irrigation, cropping information .....)
How do you use the information ? ...
How do you use the information ? ...
• System capacity — gpm/ac or in./d or an estimate of ‘application efficiency’
• Crop data – Planting date
– Type of hybrid for corn or sorghum
• System capacity — gpm/ac or in./d or an estimate of ‘application efficiency’
• Crop data – Planting date
– Type of hybrid for corn or sorghum
0
0.1
0.2
0.3
0.4
0.5
0.6 D
aily E
T, in
./d
0
5
10
15
20
25
30
35
Cu
m. R
ain
or E
T, in
.
120 140 160 180 200 220 240 260 280 Day of Year - 1995
1995 Soybean
Cum ET
Cum. Rain
Mean ET
}
6 gpm/ac
1.2 in. @ 6 gpm/ac
5 gpm/ac
1.8 in. @ 5 gpm/ac
4 gpm/ac
2.6 in. @ 4 gpm/ac
What Value is the PET Information ?What Value is the PET Information ?
• Provides useful regional information– rainfall
– soil temperatures (planting guides)
– data are being used in pest models
– quantifies water needs
– indicates crop development rates
• Provides useful regional information– rainfall
– soil temperatures (planting guides)
– data are being used in pest models
– quantifies water needs
– indicates crop development rates
What Value is the PET
Information ? ...
What Value is the PET
Information ? ...• Water savings
– could reduce pumping costs by $2-5,000 for a 1,000 ac irrigated farm by saving only 1 inch of water
• Avoid uncertainties in climatic damages– late spring freezes on wheat
• Water savings– could reduce pumping costs by $2-5,000
for a 1,000 ac irrigated farm by saving only 1 inch of water
• Avoid uncertainties in climatic damages– late spring freezes on wheat
What Value is the PET
Information ? ...
What Value is the PET
Information ? ...• LOOK at the PET data as a valued “new
tool” or accessory– keep maintaining accurate records
– keep doing plant and soil water sampling
– keep monitoring irrigation system performance
• LOOK at the PET data as a valued “new tool” or accessory– keep maintaining accurate records
– keep doing plant and soil water sampling
– keep monitoring irrigation system performance
PET ToolsPET Tools
• Can be used as a periodic guide post (twice a week or so) to see if you are applying enough water
• Provides crop consultants uniform data that they can utilize for customer portfolios
• Can be used as a periodic guide post (twice a week or so) to see if you are applying enough water
• Provides crop consultants uniform data that they can utilize for customer portfolios
NP PET Webhttp://amarillo2.tamu.edu/nppet/petnet1.
htm
NP PET Webhttp://amarillo2.tamu.edu/nppet/petnet1.
htm
Data:by station10-current9 archivedfax pageshourly data
SP (Lubbock) PEThttp://achilleus.tamu.edu/
SP (Lubbock) PEThttp://achilleus.tamu.edu/
Lubbock, Lamesa,& HalfwayCurrent PET & GDDArchived data:Lubbock since 1994Lamesa since 1996Halfway since 1996
Texas Evaporanspirati
onWeb Site
http://www.agen.tamu.edu/wqit/petnet/
Texas Evaporanspirati
onWeb Site
http://www.agen.tamu.edu/wqit/petnet/20 stations
some with databack to late 1996.Interactive wateruse calculator,Kc data, etc.
Other ExamplesOther ExamplesHigh PlainsClimate CenterUniv. of Nebr.http://hpccsun.unl.edu/
Models / Data SitesModels / Data Sites• New Mexico State Climate Center
– http://weather.nmsu.edu/
• ET Models (Silsoe College in England)– http://spider.silsoe.cranfield.ac.uk/mig/
SilsoeModels.htm
• SWIM v2 (CSIRO Australia)– http://www.clw.csiro.au/products/swim/
index.htm
• New Mexico State Climate Center– http://weather.nmsu.edu/
• ET Models (Silsoe College in England)– http://spider.silsoe.cranfield.ac.uk/mig/
SilsoeModels.htm
• SWIM v2 (CSIRO Australia)– http://www.clw.csiro.au/products/swim/
index.htm
ET ResourcesET Resources“Evapotranspiration and IrrigationWater Requirements”M. E. Jensen, R. G. Allen, and R. D.Burman
(ASCE Manuals and Reports onEngineering Practice No. 70)ISBN: 0-87262-763-2Published: 1990, American Society ofCivil EngineersList $72.00 / Members $54.00American Society of Civil Engineers1801 Alexander Bell DriveReston, VA 20191-44001-800-548-2723 or 1-703-295-6300http://www.pubs.asce.org
“Irrigation Water Requirements”D.L. Martin and J.R. Gilley
(Chapter 2, Part 623, NationalEngineering Handbook)Published: September 1993USDA-NRCSNEH-623-2Consolidated Forms and Publ.Distribution Center3222 Hubbard Rd.Landover, MD 20785
The EndThe EndUSDA-Agricultural Research Service
in cooperation with the
Texas Agricultural Experiment Station
and the Texas Agricultural Extension Service
serving the U.S. and Texas
so we can have food and fiber forever!
USDA-Agricultural Research Service
in cooperation with the
Texas Agricultural Experiment Station
and the Texas Agricultural Extension Service
serving the U.S. and Texas
so we can have food and fiber forever!