2017 Nebraska Water Center Spring Seminar

1. Advancements in Irrigation Technology
and their Impact on Water Management
Spring2017WaterSeminarSeriesLincoln,NE
March15,2017
DaranR.Rudnick,Ph.D.
AssistantProfessor:IrrigationSpecialist
DepartmentofBiologicalSystemsEngineering
WestCentralResearchandExtension Center
UniversityofNebraska-Lincoln
Phone:(308)696-6709,Email:daran.rudnick@unl.edu

2. Personal Background
• Hometown: South Sioux City, Nebraska
• Education:
• B.S. Biological Systems Engineering, UNL, 2011
• M.S. Agricultural and Biological Systems Engineering, UNL, 2013
• Ph.D. Agricultural and Biological Systems Engineering, UNL, 2015
• Appointment:
• Irrigation Management Specialist (50% Research/ 50% Extension)
Hometown
South Sioux City, NE
WCREC
North Platte, NE
UNL
Lincoln, NE

3. Research Team
• Turner Dorr: Irrigation Research
Technologist II
• Tsz Him Lo: PhD Graduate Research
Assistant
• Jasreman Singh: MS Graduate Research
Assistant
• Jacob Nickel: Irrigation Research
Technician
• Bridgett Dorr: Program Assistant
Himmy Lo Jasreman Singh
Turner Dorr
& Bridgett Dorr

4. Acknowledgement
This study is based upon work that was jointly supported by the National Institute of Food and
Agriculture, U.S. Department of Agriculture (USDA-NIFA) under award numbers 2016-68007-
25066 and 2016-68008-25078, United States Geological Survey Section 104B under award
number G16AP00068, and the Daugherty Water for Food Global Institute under award
number 01117420. Also thankful for industry support through providing equipment and
services.

5. Why do we Irrigate???
When precipitation and stored soil water in the crop root zone are insufficient to
meet crop evapotranspiration (ET) demand, irrigation is required.
Insufficient Irrigation can reduce:
• Total Biomass
• Grain Yield
• Grain Quality
• Net Return ($ per ha)
Excessive irrigation can result in:
• Runoff
• Soil Erosion
• Deep Percolation of Water (and Nutrients)
• Environmental Degradation
• Anaerobic Soil Conditions (Yield Penalty)
• Increased Pumping Cost (i.e., energy cost)
Source: Irmak (2009), Rudnick and Irmak (2015)

6. Nebraska Precipitation
Precipitation, mm
100 - 200
200 - 250
250 - 300
300 - 350
350 - 400
400 - 450
450 - 500
500 - 550
550 - 650
> 650
2000 2005
2010 Lng-Term
Avg.
Precipitation Increases West to East Irrigation Increases East to West
Source: Rudnick et al. (2015)

7. Nebraska: Density of Registered Irrigation Wells
2007

8. Nebraska: Nitrate Groundwater Contamination
Recorded concentration of nitrate (NO3) in irrigation wells from 1974 to 2012 (Quality-
Assessed Agrichemical Database for Nebraska Groundwater, 2013).
EPA Maximum Contamination Level (MCL) is 10 ppm

9. Effects of Over- or
Under Irrigating
Impact of Water Stress
Full Irrigation Deficit Irrigation Rainfed
Source: Jeff Golus
Runoff and Soil Erosion
Source: Pioneer.com
High Soil Water Content

11. Crop Water Requirements
Depends on:
• Crop Type & Variety
• Growth Stage
• Soil Water & Nutrient Availability
• Soil Physical & Chemical
Properties
• Micrometeorological Conditions
• Among others
Corn crop water use or daily evapotranspiration (ET) from a well-watered crop.
The smooth line (A) depicts long-term daily ET and the jagged line (B) depicts
daily ET for an individual year. (Taken from UNL NebGuide G1850,
http://extensionpublications.unl.edu/assets/pdf/g1850.pdf).
Corn Water Use (inch per day)

12. Water Demand from Various Sectors
Climate
Industry

13. Groundwater Declines in the Ogallala Aquifer
• Water level changes in the High Plains
Aquifer, pre-development through
2007
• Groundwater is connected to surface
water
• Reduction in groundwater levels can
limit water available for irrigation
• Consequently, restrictions have been
enforced in areas to sustain and/or
extend the useable life of the aquifer
for future generations
Source: McGuire (2009) as modified from Lowry et al. (1967); Luckey et al.
(1981); Gutentag et al. (1984); and Burbach (2007). Taken from Konikow (2013)

14. • Nebraska Natural Resource Districts (NRDs) water management
regulations can include:
• Allocating groundwater
• Augmenting surface water
• Requiring flow meters
• Instituting well drilling moratoriums
• Requiring water use reports
• Restricting expansion of irrigated acres
Nebraska Natural Resource Districts
Allocations Updated February 2014
• Upper Niobrara-White NRD
• 54” per 4 years
• North Platte NRD
• 70” per 5 years
• & Pumpkin Creek = 36” per 3 years
• South Platte NRD
• 42 to 54” per 3 years (by subarea)
• Upper Republican NRD
• 65” per 5 years
• Middle Republican NRD
• 60” per 5 years
• Twin Platte NRD
• No allocation
• Upper Loup NRD
• No allocation
• Middle Niobrara NRD
• No allocation

15. Conventional Sprinkler Irrigation
Applying a uniform depth of water per area through the irrigation system to
meet average crop water demands of a field.
Source: pintrest.com

16. Center Pivot (1960’s)

17. Irrigation Distribution Uniformity
1.
2.
4.
3.
Source: ASAE (2003)
Source: Chuck Burr

18. Mobile Drip Irrigation (MDI)
System Types
• Sprinkler (Senninger IWob) & MDI
Irrigation Levels
• Full, Deficit, & Rainfed
Residue Levels
• No-Removal & Baling

19. MDI Research
• Preliminary Results
• Similar grain yields and kernel weights
across system types
• Future Research Efforts
• Crop Water Use (ET)
• Long-term trends in production & water use

20. Variable Rate Irrigation
System Description

21. Variable Rate Irrigation (VRI)
Applying variable depths or rates of water through an irrigation system to
meet differences in crop water demands, soil conditions, and/or other
constraints.
0.60 – 0.90 m
0.30 – 0.60 m
0 – 0.30 m
Available Water Capacity, mm
Source: Rudnick and Irmak (2014a, 2014b)

22. Types of VRI
Depending on system and controller VRI can be managed in sectors, bank of sprinklers,
or individual sprinklers.
Fixed Zone Control Irregular Zone ControlSector/Speed Control

23. Speed/Sector Control
• Changes end tower speed at specified
angular positions
• Modifies application depth in sectors of
the circular pass
• Alters application duration but not
application intensity
• Does not affect sprinklers, system curve,
or pump performance curve
Sector/Speed Control
15 mm 20 mm
25 mmapplication
intensity
time
at a given
radius
from pivot
point

24. Sprinkler Control
• Changes discharge of individual or banks of
sprinklers
• Relies on valves directly upstream from
sprinkler
• Changes in sprinkler discharge achieved by
pulsing
• Turns off a sprinkler for a fraction of a cycle
• Optimizes timing to minimize flow rate
oscillations
• Modifies application depth in more flexibly
shaped zones as compared to sector control
Solenoid Valve
Pressure Regulator
Sprinkler

25. Video of Pulsing Sprinklers

26. Sprinkler Control
• Individual or groups of sprinklers (i.e.,
banks of sprinklers)
• Changes in application depth
accommodated by
• Speed of pivot
• Pulsing of sprinklers
• Management zone must be greater than
sprinkler throw diameter (consider
sprinkler overlap!). More zones = more
work!
Fixed Zone Control
15 mm
20 mm
25 mmapplication
intensity
time
sprinklers at
a given
radius from
pivot point
Irregular Zone Control

27. Example: Fixed Zone Pivot at Big Springs, NE
Span 1 - 6: On
Span 7-8: Off
Primary Valve
Secondary Valves
Smallest Zone
1ᵒ Change
Span Control
Controller

28. Example: Sprinkler Controlled Pivot at Grant, NE

29. Variable Frequency Drive (VFD)
• VFD speeds up or slows down
the pump motor to reach a
desired operating pressure or
flow rate
• Adopting VFD will depend on
flow rate & pressure changes
within the system (is it
economical?)
• High or premium efficiency
motors are often required

30. Irrigation Management Technology
Benefits & Challenges

31. Irrigation and N Fertilizer Management
A primary research and production goal is to further improve irrigation and
nitrogen use efficiency to enhance economic return as well as prevent
environmental degradation. Addressing the following will aid in this effort.
• Reduce uncertainty in measuring/estimating crop water and nitrogen
requirements
• Account for spatial and temporal differences in crop water and nitrogen demand
• Accurately apply inputs to minimize losses
• Irrigation: runoff, percolation, evaporation
• Nitrogen (depends on N type): volatilization, leaching, de-nitrification, runoff
• Concurrently manage irrigation and nitrogen fertilizer
• Fertigation is a step forward in this direction

32. Some Useful Information for Irrigation
Management
Information (Source):
• Historical Records (Yield data, compaction issues, etc.)
• Soil Properties (NRCS soil surveys, ECa mapping)
• Topography (DEM-digital elevation maps via survey, LiDar, etc.)
• Field Conditions (Residue level, pest pressure, nutrient availability, etc.)
• Visual Observations (Drainage ways, streams, roads, etc.)
• Soil Water Status (Soil water sensors)
• Evaporative Demand (Climatic variables via weather station)
• Crop Water Stress (Thermal sensors)
• Crop Growth and Condition (Canopy reflectance, visual imagery, and crop models)
• Remote Access to System (Telemetry)
• System Performance (Pressure transducers, telemetry, etc.)

33. Management Zone Delineation
• Apparent Electrical Conductivity (ECa)
• Easy to measure and relatively low cost
• Indirect indicator of important soil physical and chemical
characteristics
• Commonly used for VRI application
• Some Factors Impacting ECa
• Clay content and mineralogy
• Soil salinity
• Cation exchange capacity
• Soil pore size distribution
• Temperature
• Organic matter content
• Soil water content
Source: Rudnick and Irmak (2014)

34. ECa Response Curve vs. Rooting Depth
Source: Irmak and Rudnick, 2014
Crop Type Total Rooting
Depth (ft)
Effective Rooting
Depth (ft)
Alfalfa 8 – 12 4 – 5
Corn 5 – 6 3 – 4
Sorghum 6 – 7 3 – 4
Soybean 5 – 6 2 – 3
Winter Wheat 4 – 5 2 – 3
Mature Growth Stage, under well drained, deep silt loam soils

35. ECa vs. Soil Hydraulic Properties
Sources: Rudnick and Irmak (2014)
𝐴𝑊𝐻𝐶 = 𝐹𝐶 − 𝑊𝑃 × 𝑅𝐷
AWHC: Available Water Holding Capacity
FC: Field Capacity
WP: Wilting Point
RD: Rooting Depth
Soil Type Available Water (in/ft)
Silt Loam 2.5
Sandy Clay Loam 2.0
Silty Clay Loam 2.0
Silty Clay 1.6
Sandy Loam 1.4
Loamy Sand 1.1
Fine Sand 1.0

36. Available Water
Diagram for Irrigation using Soil Water Sensors
Management
Zone
Water Freely Drains
Crop Water
Stress Zone
Water Not
Available to the Crop
Dry Soil
Saturation
Field Capacity
MAD = Trigger Point
Latest Start Date
Wilting Point
Irrigation
Soil Water
Sensor

37. Some In-Situ Soil Water Sensor Companies

38. Soil Water Sensors & ETgage
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

39. In-Field Sensor Evaluation
Sensors:
• AquaSpy
• AquaCheck
• John Deere Field Connect
• Hortau
• Decagon 5TE, EC5, MPS-2, MPS-6
• Stevens Hydraprobe
• Acclima TDR315
• Campbell Scientific CS616 & CS655
• CPN Neutron Gauge
• Irrometer Watermark, Tensiometer
Year: 2016
Location: North Platte, NE
Crop Type: Soybean
Loam Soil  little salinity

40. In-Field Sensor
Performance
• All Sensors tended to
over-estimate
θv (m3 m-3) Combined Depths
Sensor MD SDD RMSD
TDR315 0.047 0.019 0.050
CS655 0.056 0.055 0.078
HydraProbe2 0.095 0.036 0.102
5TE 0.036 0.015 0.039
EC5 0.048 0.026 0.054
CS616 0.149 0.051 0.157
Field Connect* 0.079 0.027 0.083
AquaCheck* 0.162 0.017 0.163

41. Evaluation of Calibration Techniques
• Offset Calibration
• 2 Point Calibration
• Regression Fitting
• Retention Fitting
• Laboratory Calibration
Offset Example:
• Take one accurate
measurement in-season
• Offset all other points
• Assumption: Regression
response is linear with a slope
of 1
Well-Performing Offset Calibration

42. In-Field Regression
Calibrations
Regression Response
• 5 Linear and 19 Quadratic
Linear Responses
• Estimate of intercept > zero
• Linear Coefficient < one
• Sensors are more sensitive
than reference
Quadratic Responses
• Sensitivity generally increased
with θv within the observed θv
range

43. Laboratory Calibrations
• Most sensors tended to over-
estimate θv in the lower observed θv
range.
• Variability in sensor performance
was observed between lab and field
calibrations.

44. Laboratory Calibration Techniques
Repacked versus Intact Soil Cores
• Different drying trends
• Repacked slightly underestimated water content

45. Statewide Soil
Experiment
• Five Soil Types
• Four Salinity Levels
• Two Sensors Evaluated
• TDR 315 & CS655
weight % of
soil solids
weight % of mineral fraction g cm-3
Soil
Organic
Matter
Sand Silt Clay
Target Bulk
Density
V 0.2 (0.0) 88 (1) 7 (1) 5 (1) 1.6
C 2.1 (0.1) 55 (3) 23 (3) 22 (0) 1.3
K 2.6 (0.1) 35 (2) 35 (3) 30 (2) 1.3
H 2.4 (0.1) 14 (3) 40 (5) 46 (2) 1.4
W 2.5 (0.1) 8 (4) 42 (1) 49 (4) 1.4

46. Instrumentation for VRI Research
Research Questions
• How to collect and analyze different
information of various spatiotemporal
resolutions to inform VRI scheduling and
prescription generation?
• Would VRI affect nitrogen management?
If so, how can irrigation and nitrogen
management be optimized
simultaneously?

47. Year 1 Management Zones and Treatments
• Two management zones—one consisting of gravelly soils and another
consisting of non-gravelly soils
• Zones were delineated using ECa, assuming lower ECa represents gravelly soils
• Full irrigation (F):
attempt to eliminate
any water stress
• Conventional (C):
uniform irrigation
based on the
non-gravelly soil
• Deficit irrigation (D):
allow water stress during
less sensitive growth stages
• Non-irrigated (R): no irrigation

48. Sprinkler Controlled Pivot at Brule, NE

49. Point-Based Water Status Data
AquaCheck
multisensor
capacitance
probe
neutron
moisture meter
wireless
infrared
thermometer
scaled
frequency
units
0
50
100
150
200
250
300
D F C R D F R
TotalWaterin0-0.9m
June 23rd, 2016
0-0.3 m
0.3-0.6 m
0.6-0.9 m
non-gravellygravelly
irrigation:
soil:
0
50
100
150
200
250
300
D F C R D F R
TotalWaterin0-0.9m
October 3rd, 2016
0-0.3 m
0.3-0.6 m
0.6-0.9 m
non-gravellygravelly
irrigation:
soil:
0
5
10
15
20
25
30
35
0:00 8:00 16:00 0:00 8:00 16:00 0:00
SurfaceTemperature(°C)
Time
fully irrigated
deficit irrigated

50. Visible Imaging
deficit
irrigatedfully
irrigated
deficit
irrigatedfully
irrigated
August 1st, 2016 (silking) September 26th, 2016 (30% milk line)

51. Thermal Infrared Imaging aerial image taken by AirScout
ground-based images taken using FLIR E60
non-irrigated
fully
irrigated

52. Radiometric Temperature
Instruments
• Infrared Thermometers (IRTs)
• Aerial Thermal Imagery (Airscout)
Observations
• Airscout observed smaller ranges
in Temp as well as lower Temp
values.
AirScout thermal (left) and visible (right) image of the Brule site on 9/26/2016; the 12
monitoring locations are marked and labeled, and the rainbow color scale from blue to
red in the thermal image denotes radiometric temperatures from low to high.

53. Collaborative VRI Research
• Irrigation Management using Remote Sensing
• Research project initiated at UNL Brule Water Laboratory in 2016
• Collaboration:
• Burdette Barker
• PhD Graduate Student
• UNL Biological Systems Engineering
• Derek Heeren
• Assistant Professor: Irrigation Engineer
• UNL Biological Systems Engineering
• Christopher Neale
• Director of Research
• Water for Food Daugherty Global Institute

54. WCREC Research
Site: Brule, NE
Elevation (m)
Topographic Map
University of Nebraska-Lincoln
West Central Research and Extension Center
Brule Water Laboratory near Brule, NE
0 - 2
2 - 4
4 - 6
6 - 8
8 - 10
10 - 12
Slope (%)
Soft Edge
1073 - 1075
1070 - 1073
1067 - 1070
1064 - 1067
1061 - 1064
1058 - 1061
1055 - 1058
1052 - 1055
1050 - 1052
±

55. Irrigation Management Using Remote
Sensing
Multispectral
Imagery(Spatial–
LowTemporal)
Soils Map
Weather Data
(High Temporal)
Previous
Irrigation Maps
New Irrigation
Prescription and
Schedule
RS – Based
Hybrid Water
Balance Model
Neale, C.M.U., Geli, H.M.E., Kustas, W.P., Alfieri, J.G., Gowda, P.H., Evett, S.R., Prueger, J.H., Hipps, L.E., Dulaney, W.P., Chavez, J.L., French, A.N.,
and Howell, T.A. (2012). Soil water content estimation using a remote sensing based hybrid evapotranspiration modeling approach. Advances
in Water Resources, 50, 152-161.

56. VRI System at Research Center

57. Experimental Layout at WCREC
• Treatments
• RS-based VRI management
• Conventional or “uniform”
management using water
balance
• Blocked by available water
capacity zones (determined
from neutron probe and soil
series)
• Continuous maize crop ~49 ha
• Individual sprinkler zone control
VRI Aerial Image Source: USDA-FSA (2014). USDA-FSA-APFO NAIP MrSID
Mosaic for Keith County, Nebraska. U.S. Department of Agriculture,
Aerial Photography Field Office, National Agricultural Imagery Program.

58. Preliminary Results WCREC
Irrigation Depth:
• Conventional: 324 mm
• VRI w/ Remote Sensing: 342 mm
Variability in seasonal irrigation amount.

59. Fertigation Research
Demonstrate the potential for improving nitrogen use efficiency (NUE) while
optimizing profitability through the use of canopy reflectance and crop N modeling
techniques.
• Collaboration:
• Brian Krienke
• Suat Irmak
• Richard Ferguson
• Tim Shaver
• Charles Shapiro
• Keith Glewen
• Locations:
• West Central Research and Extension Center, North Platte, NE, USA
• South Central Agricultural Laboratory, Clay Center, NE, USA

60. Variable Rate Fertigation (VRF)
Applying variable amounts or rates of fertilizer
through an irrigation distribution system to meet
spatial and temporal differences in crop nutrient
demands, soil conditions, and/or other constraints.
VRF Scenarios:
• VRF with variable rate fertigation pump
• Uniform Irrigation and Variable Fertilizer
• Variable Irrigation and Uniform Fertilizer
• VRF with constant rate fertigation pump
• Use VRI technology with uniform fertilizer speed

61. Thank You!
The mention of trade names or commercial products in and during this
presentation does not constitute an endorsement or recommendation for
use by the University of Nebraska-Lincoln or the author.