soybean irrigation management · •available in apple and android platforms •figure how well...

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© 2016 University of Nebraska–Lincoln

Soybean Irrigation Management

Daran Rudnick-Extension SpecialistChuck Burr and Troy Ingram -Nebraska Extension Educators


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)


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


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


Concepts for Managing Irrigation with Soil Water Sensors

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Soil Water

Diagram for

Irrigation

Scheduling


• 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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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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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


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.


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


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


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


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


• Soywater on Cropwatch

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• Login page


• Soywater inputs

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• Output table

– Input rainfall

– Input irrigation

• Soil water depletion

• Predict growth Stages


• Water use chart

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• Watermark sensor calculator


Nelson Senninger

Regulators Function the Same

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Pressure Regulator Tester


Pressure Regulator Tester

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Thank You!


acres

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http://water.unl.edu/cropswater/nawmn

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https://nawmn.unl.edu/


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