Soil moisture monitoring
For irrigation water management
Caleb M. CarterU.W. Extension EducatorGoshen County2014 SE Wyoming Beef Production ConventionTorrington, WYNovember 18, 2014
Outline• Why…
• How…
• What for…
• Soils• Options• Placement• Data
“And we can save 700 lira by not taking soil
samples!”
Importance of soil sampling!
Web soil survey
http://websoilsurvey.sc.egov.usda.gov/App/HomePage.htm
Can be a good, quick way to learn more about your soils
Challenges…
When and how much?
Water holding capacity
• Texture/rocks
• Organic matter
• Bulk density
• Structure
• Rooting depth
• Past management
Water holding capacity
Saturation Field Capacity
Permanent Wilting Point
• Field capacity
(FC)
• Wilting point
(WP)
Available water capacity
Management allowable depletion (MAD)
Take half, leave
half…
…works for water
too
• Accuracy not as
important
• Irrigation system
limitations
• Crops and soils
• Time investment
• Be realistic
Considerations
OptionsGypsum blocks
Watermark blocks
Tensiometers
The feel method
Feel method• If it makes a ball and
falls apart when you
bounce it in your hand,
needs irrigation
Centibars
Tensiometers
• Cost depends on length:
• 6 – 48”/$45 to $80
• Read 0 to 80 centibars
Electrical resistance blocks
Gypsum Granular matrix sensors
• 1 to 2 years• $5 to $15 apiece
• Best in fine soils
• More sensitive to
freezing
• 5 to 7 years• $25 to $30 apiece• Wider range of soil
moisture
Watermark block install
Watermark block install
Installing a WATERMARK Sensor on PVC in Hard or Rocky SoilIRROMETER Company, Inc.
Reading data
Placing sensors
Soil variationUse soil with the
smallest water
holding
capacity, if 30
to 50% of the
field
Active root zone
Depth of root zone determines depth of monitoring
• 1/3 and 2/3 of the active root zone
Field placement
Using the data
Graphing data
Checkbook method
What goes in…
…must come out
Checkbook methodStarting the checkbook
• soil texture
• crop type, rooting depth and
water use
• available water-holding capacity
of the soil
• minimum allowable balance
• estimate of current soil water
balance.
Considerations…• You know your fields, crops and irrigation
systems best
• Adjust, adapt or reject suggestions
• Not a substitute for personal observations
Trial and error
Implementing new recommendations
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