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

Questions?Caleb M. Carter

UW Extension Educatorccarte13@uwyo.edu