Ted Harms.pdf

Soil Moisture Monitoring
for Irrigation Scheduling
T.E. Harms Irrigation Management
AAF, Brooks AB.

Soil Moisture Instrument
Evaluation
• 4 year study that is still continuing
informally.
• Criteria for Soil Moisture Instruments
• Cost Effective (~$1000 Cdn)
• Portable
• Reasonable Accuracy
• Easily Understood Visual Display
• Immediate Display
• No Special Training

COMPARISON OF VARIOUS
MODES OF PROBE
INSTALLATION FOR PROFILING
Soil
Auger
Moisture•Point
C Probe
PF-1
Single segment
TDR and
Capacitance
Access Tube
Probes
TDR and Capacitance
Forks and Buried Type
Probes,
Gypsum Blocks
Neutron Probe for
Access Tube, RF
Sensor
Gravimetric
Method

Soil Moisture Instruments
Evaluated for Irrigation Scheduling

Pros and Cons
• Pros and cons with all sensors
• CPN 503 DR is the standard but its storage,
use, certification is strictly regulated.
• Capacitance sensors are sensitive to soil
salinity and change based on soil bulk
density.
• Soil potential probes have limited range up to
–200
cbars.
• They all work and the choice depends on the
application desired.

RomComm Kelowna
Brooks
Soil Moisture Sensor, Pivot
in Lethbridge, AB

120
Available Water Content (%)
100
80
60
40
Turn Pivot Off
Turn Pivot On
20
0
10-May 20-May 30-May 9-Jun 19-Jun 21-Jul 31-Jul 10-Aug
Date

Zimmatic’s New GrowSmart
Technology

Irrigation Strategies
1 week
Root zone full
0-15”
20”
Allowable depletion
30”

Limited Adoption of Soil Moisture
Sensors for Irrigation Scheduling
• Expense is not worth the information provided.
• Too complicated - installation, learning curve for
use, interpretation.
• Effort is not worth the result.
• Point measurement in field.
• Time consuming.
• No local support.
• Interest and use primarily by consultants and
industry field personnel.

ET Based Irrigation Scheduling
• Alberta Irrigation Management Model
(AIMM)
• Desktop
• Irrigation Management Climate Information
Network (IMCIN)
• Web-based
based

Advantages
• Many irrigators are farming increased area and are
not as “intimate” with individual fields.
• Daily information regarding the soil moisture status
of your fields.
• Can prioritize time to concentrate on the fields
requiring irrigation.
• Anticipate irrigation need rather than react to soil
moisture shortage or crop stress.
• Assists decision making for efficient and effective
irrigation scheduling.

Information can be provided as:
• Pull – require user to request information (How
most automated pivot systems work – how IMCIN
works).
• Push – deliver information to the user (Increasing in
use with consultants, producer groups – most
attractive option for irrigators).
• Plug – allow user to maintain hands-on contact with
data source (AIMM – desktop application).
(Magarey
et al., 2002)

Example of Graphical Output from
AIMM

Example of Information from
IMCIN Website

Conclusions
• Soil moisture sensors for irrigation scheduling –
limited adoption in Southern Alberta.
• Advanced features supplied by pivot manufacturers
for continuous soil moisture measurement and
information – no adoption that presenter aware of
in Southern Alberta.
• ET based scheduling tools – estimated about 15% of
irrigated area in Southern Alberta using AIMM for
irrigation scheduling.
• IMCIN increasing in utility and use – developing
disease forecasting and urban watering.