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Soybean Irrigation Management
Daran Rudnick-Extension SpecialistChuck Burr and Troy Ingram -Nebraska Extension Educators
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Importance of Irrigation
Source: Rudnick and Irmak (2015)
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Periods When
Crops are Most
Susceptible to
Water Stress
[a]Pollination period very critical if no prior water stress.
Source: Doorenbos and Pruitt (1977)
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Yields by
Irrigation
Strategy
http://extensionpublications
.unl.edu/assets/html/g1367
/build/g1367.htm
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Monsanto Water
Utilization
Learning Center
2010
Corn
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Monsanto Water
Utilization
Learning Center
2010
Soybeans
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Average Soybean Yield and Irrigation Water Use Efficiency for all sites in 2015
Treatment SoybeanYieldbu/ac
Irrigationinches
Irrigation Water Use Efficiencybu/inch
Full Irrigation 81.7 3.0 0.1
75% Irrigation 80.2 1.9 -0.6
50% Early,Full After R3 83.6 1.3 1.8
Rainfed 81.3 0.0
Average Rainfall 17.1 inches
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Concepts for Managing Irrigation with Soil Water Sensors
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Soil Water
Diagram for
Irrigation
Scheduling
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• Indirect methods measure a surrogate property and relate it to soil water content or potential.
• Some Indirect methods
– Hand Feel
– Neutron Attenuation
– Capacitance
– Time Domain Reflectometry
– Frequency Domain Reflectometry
– Electrical Resistance
– TensiometersEstimated
Soil Water Status
Measure Variable
“Surrogate”
Relationship
(a.k.a. Conversion)
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© 2016 University of Nebraska–Lincoln
Campbell Scientific CS616
SWC
Campbell Scientific CS655
SWC, Temp, & EC
MPS-2 or MPS-6 5TE EC-5
SWP & Temp SWC, Temp, & EC SWC
---------- Decagon Devices ----------
Stevens Hydra Probe II
SWC, Temp, & EC
Acclima True TDR
SWC, Temp, & EC
Irrometer Watermark
SWP
Irrometer Tensiometer
SWP
ETgage (Atmometer)
Reference ET
Legend:
SWP: Soil Water Potential
SWC: Soil Water Content
Temp: Soil Temperature
EC: Bulk Electrical Conductivity
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© 2016 University of Nebraska–Lincoln
Electrical Resistance Sensors
Description:
•Relatively low cost & easy to use/install
•Reports “tension” not “water content”
•Requires good soil contact
•Some issues with high sandy soils at high tensions or
swelling clays
•Minor Temperature effects
•Tension decreases by 1% for each 1ᵒF increase above
70ᵒF & vice versa
•Response Time (potential lag)
•Hysteresis Effects (i.e., wetting and drying curves are
not the same)
Gypsum BlocksWatermark
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Tensiometers
Description:
•Operational range: 0 to ~85 cb
•Within irrigation range for sandy soils
•Not within irrigation range for fine-textured soils
•Potential limitation on depth of install
•Reports “tension” not “water content”
•Requires good soil contact
•Response Time (potential lag)
•Hysteresis Effects (i.e., wetting and drying curves are not
the same)
•Routine maintenance
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Capacitance Sensors in Access Tubes
Description:
•Based on dielectric properties of soil
•Capacitors can often be placed at various
depths within access tube
•Continuous monitoring capabilities
•Fast response time
•Susceptible to various factors: soil type and
structure, temperature, wetting patterns, soil
salinity, air gaps, clay content, among others
•Proper installation is essential
•Measurement frequency impacts the sensing
volume
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•Field evaluation is necessary to determine
how well the sensors will perform under
dynamic in-season conditions.
•Laboratory evaluation using site specific soils
can help identify the accuracy and precision of
the sensors.
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Laboratory Sensor
Comparison
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Select
Sensor
• Convenience
• Financial Cost
• Remote Access
• Sensor Accuracy
• Product Support
• Soil Type & Condition
• How Many are Needed
• Crop Type and Rooting Depth
• Integration with Other Sensors
Pros vs Cons
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Crop Water App• Free App• Available for Apple/Android• Provides an easy way to estimate soil
water status• Will estimate water used/water
available• Log readings over time
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CropWater• Calculate average reading down to 4 feet
• Water depleted in inches/foot
• Calculate water depleted in soil profile
• Also displays total water available
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CropWater
© 2016 University of Nebraska–Lincoln
IrrigatePump• Cost - $3.99• Available in Apple and Android platforms
• Figure how well your pumping plants on your irrigation wells stack up against the Nebraska Pumping plat Criteria (NPC)
• Should be a reasonable target for every new pumping plant
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IrrigatePumpResults:
• Click on the “Calculate” button to figure your performance rating
• Figures potential savings if you could bring the unit up to NPC standard
• Also figures payback years
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MeterCalc
• Acre inches pumped displayed
• Inches per acre displayed
• Total inches pumped during season
• Tracks annual allocations
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Soywater:- Launched on May1, 2010- Irrigation management tool- Developed by UNL & Nebraska Soybean Board
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• Soywater on Cropwatch
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• Login page
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• Soywater inputs
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• Output table
– Input rainfall
– Input irrigation
• Soil water depletion
• Predict growth Stages
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• Water use chart
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• Watermark sensor calculator
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Nelson Senninger
Regulators Function the Same
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Pressure Regulator Tester
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Pressure Regulator Tester
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Thank You!
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acres
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http://water.unl.edu/cropswater/nawmn
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https://nawmn.unl.edu/
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© 2016 University of Nebraska–Lincoln