Soil Moisture Monitoring
By: Matthew DeBacco
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Disclaimer:
• I have not used any of the sensors depicted in this
presentation, but I have used WatchDog data loggers and
have experience with other data loggers.
• I am not sponsored by any of the listed companies I simply
did extensive research and I am presenting my findings.
• I hope to use the model I selected in the 2016 growing
season
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Why is it important?
• Keeping the soil moisture consistent should help
ensure even growth.
– Like consistent rings on a tree stump…
Inconsistent
watering
“Farmer calibration”
• Soil moisture monitoring devices are a way to put a
value to what is happening in the root zone.
• *However, you should be “feeling the soil” to
correlate the numbers with your actual observations
http://www.specmeters.com/assets/1/14/DimLarge/6466_2.jpg
http://www.cdpr.ca.gov/docs/county/training/inspprcd/handouts/soil_moist_feel_test.pdf
Some Soil Basic Terminology
http://www.sswm.info/sites/default/files/toolbox/BETTER%20SOIL%20ny%20Stages%20of%20Water%20Colding%20Capacity.jpg
Water your soil can hold
depends on soil type…
https://s3.amazonaws.com/soilquality-production/resources/122/original/Phys_-_Water_Availity_Fig1.PNG?1390462498
Soil types are based on composition
*Note: clay has a large influence
http://www.newagegarden.net/wp-content/uploads/2015/04/soil.gif
Which sensor to use?
• Most growers using them now, have discontinued
models. (Steve D., Ron W., Joe J.)
• Many options…
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og/product/cache/5/image/6e694897ca686320e87bff
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Many different price points
• There are different prices for different budgets
• Findings presented here are based on my research
• Keep in-mind you pay for what you get…
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Very Basic 1-10 Readings
“Homeowner models”
Etekcity Indoor/Outdoor
Soil Moisture Sensor Meter
$7.99
http://ecx.images-amazon.com/images/I/61GfDJbqWRL._SL1000_.jpg
REOTEMP MM17 Backyard
Moisture Meter
$31.00
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High end
Homeowner model
General Tools & Instruments
DSMM500 Precision Digital Soil
Moisture Meter with Probe
$189
• Does measure moisture
content with a measurement
range of 0-50%
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Two main Professional types
Watermark measures soil potential (tension) 0-200 cbars
http://fyi.uwex.edu/cropirrigation/files/2015/03/Methods.to_.Monitor.Soil_.Moisture.pdf
Watermark (Granular matrix sensor)
Advantages
• Up to 4-in. (10cm)
measurement cylinder
radius
• Minimal maintenance
needed
• Simple and inexpensive
• Salinity effects buffered up
to 6ds/m
• Suited to deficit irrigation
Drawbacks
• Low resolution
– (limited use in research)
• Temperature dependent
• Slow reaction time
• Not suited for sand soils
where water drains quicker
than instrument can
equilibrate
• If soil becomes too dry
sensor must be removed
and re-saturated/reinstalled
http://www.calafrica-sa.co.za/images/images_index/watermark_new.jpg
https://www.bae.ncsu.edu/topic/go_irrigation/docs/Field-devices-monitoring-.pdf
Two main Professional types
WaterScout Capacitance measures volumetric soil moisture
http://fyi.uwex.edu/cropirrigation/files/2015/03/Methods.to_.Monitor.Soil_.Moisture.pdf
WaterScout (Capacitance sensors)
***Recommended***
Advantages
• Accurate (+/-1%) after
soil specific calibration
• Can be used in high soil
salinity
• Relatively inexpensive
Drawbacks
• Sensing sphere is
relatively small (~1.6in
or 4cm)
• Must have good soil
contact
• Needs soil specific
calibration
http://www.labchem.biz/image/cache/data/spectrum/SMEC300-300x300.jpg
https://www.bae.ncsu.edu/topic/go_irrigation/docs/Field-devices-monitoring-.pdf
Spectrum Technologies, Inc.
• I selected this company because they offer both types of
sensors and have had recent (2011 + 2012) innovations and
awards for their Capacitance sensors
• Their technology has been used in many scientific papers
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Watermark Set-Up
Cost = $254.50
• Watermark digital Reader = $219
• Watermark Sensor = $35.50
•
………………………………………………………………………………
• Pro: Provides live readings
– Least expensive option
– Data logger optional but special requirements
• Con: You must actively take the readings
– Need to bury other sensors to get multiple
readings the same day
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http://www.calafrica-sa.co.za/images/images_products/soil_moisture_sensor.jpg
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The Simple Set-Up
Cost = $368
• FieldScout Soil Reader = $279
• WaterScout SM 100 Sensor = $89
•
………………………………………………………………………………
• Pro: Provides live readings
– Can take multiple readings around patch
• Con: You must actively take the
readings
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Data Logger with 1 sensor
Cost = $428
• WatchDog 1200 Mirco Station = $240
• SpecWare 9 Basic Software = $99
• WaterScout SM 100 Sensor = $89
•
………………………………………………………………………………
• Pro: Provides a data logger for
storing readings at a set interval and
you can access real time readings
– Can handle up to two sensors
• Con: Increased cost of $60
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Data Logger with 2 Sensors
Cost = $517
• WatchDog 1200 Mirco Station = $240
• SpecWare 9 Basic Software = $99
• WaterScout SM 100 Sensor *2 = $178
•
………………………………………………………………………………
• Pro: Provides a data logger for
storing readings at a set interval
– Can handle up to two sensors
• Con: Increased cost of $89
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Two Sensor Models…
WaterScout SM 100
WaterScout SMEC 300
*some data loggers can only handle 1 or 2 max
• Measures:
– Soil moisture
• Cost:
– 6ft cable = $89
– 20ft. Cable = $97
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• Measures:
– Soil moisture
– EC (electrical conductivity)
– Temperature
• Cost:
– 6ft cable = $219
– 20ft. Cable = $229
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SMEC 300 Sensor Upgrade
Cost = $655
•
•
•
•
WatchDog 1200 Mirco Station = $240
SpecWare 9 Basic Software = $99
WaterScout SM 100 Sensor (20ft.) = $97
WaterScout SMEC Sensor = $219
•
………………………………………………………………………………
• Pro: Provides a data logger for
storing readings at a set interval
– Will also measure temperature, EC
• Con: Increased cost of $138
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Pumpkin Growers 3 Sensor Set-up
Cost = $882
•
•
•
•
WatchDog 1525 Mirco Station = $360
SpecWare 9 Basic Software = $99
WaterScout SM 100 Sensor *2 (20ft.) = $194
WaterScout SMEC Sensor *1 (20ft.) = $229
•
………………………………………………………………………………
• Pro: Data logger also has internal (air)
temp. to compare with soil readings
– Uses three total sensors
• Con: Highest cost
– Could add another SM 100 for $89 more
(or $971 total)
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Sensor location can be important…
• Varies based on soil type and sites
• Key part is you want to be in the root zone
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Models of Data Loggers to keep in mind…
WatchDog 1000 Micro Stations
• External Sensors Only = $240-$310
• Internal Temperature Sensor = $255-360
• Internal Temp. + Relative Humidity = $300-445
– Price range due to how many external ports
– Typically 2-4 ports
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Data Loggers can handle other sensors
Important Links:
• Spectrum Technologies Website:
– http://www.specmeters.com/
• Soil Moisture Sensor Options:
– http://www.specmeters.com/soil-and-water/soil-moisture/soil-moisture-sensors/
• WatchDog 1000 Series Micro Stations: (data loggers)
– http://www.specmeters.com/weather-monitoring/data-loggers/1000-microstations/
• Methods to Monitor Soil Moisture:
– http://fyi.uwex.edu/cropirrigation/files/2015/03/Methods.to_.Monitor.Soil_.Moist
ure.pdf
• Performance Evaluation Volumetric Soil Water vs. Soil Water Potential
– https://www.ksre.k-state.edu/irrigate/oow/p11/Chavez11.pdf
• Estimating Soil Moisture by Feel and Appearance:
– http://www.cdpr.ca.gov/docs/county/training/inspprcd/handouts/soil_moist_feel_
test.pdf