Soil Sampling & Testing

Advanced Soils Topics for Master Gardeners

Amy ShoberUF-IFAS Gulf Coast REC

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Tools for Collecting Soil

• Plastic bucket• Shovel or soil

probe• Paper bag or

newspaper for drying

• Soil test sample bag

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Taking a Soil Sample

• Representative area

• Sample the root zone depth

• Take & mix several cores together

• Do not mix cores from “good” & “bad” areas

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Figure Credit: Amy Shober, UF-IFAS

ESTL RecommendationsTurfgrass Ornamentals/Vegetables

Bahiagrass Azaleas

Bermudagrass Blueberries

Carpetgrass Camellias

Centipedegrass Dooryard Citrus

Ryegrass Gardenia

St. Augustinegrass

Hibiscus

Zoysiagrass Ixora

Woody ornamentals (general)

Vegetables4 of 13

©2008 University of Florida-IFAS

UF-ESTL Available TestsTest A ($3.00)• pH• Lime requirement

Test B ($7.00)• Test A +• P, K, Mg

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Photo Credit: Amy Shober, UF-IFAS

pH vs. Lime Requirement

Soil pH Test• Measures active acidity

– pH that affects plant growth

Lime Requirement Test

• Also called buffer pH• Measures reserve

acidity• Uses a liming solution• Compared to soil pH• Measures how easily

pH can be changed– Bigger change means

easier to change pH

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Photo Credit: Amy Shober, UF-IFAS

Why Measure Buffer pH?

• Active acidity(solution) and reserve acidity (bound to clay and OM particles)

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Figure Credit: James Bonczek, UF-IFAS

Why Measure Buffer pH?

• Lime (calcium carbonate) neutralizes acid in the soil solution & pH increases.

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Figure Credit: James Bonczek, UF-IFAS

Why Measure Buffer pH?

• Ca2+ displaces H+ on the surface of clays or OM and pH drops back down.

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Figure Credit: James Bonczek, UF-IFAS

Testing Soils for Plant Available Nutrients

• Chemical extractants are used• UF-IFAS uses the Mehlich 1

extractant– Developed by Dr. Adolph Mehlich (NC)– Good for P, K, Ca, Mg, Zn, Mn, and B– Good for acid, low fertility soils

• Nitrogen testing not available due to dynamic nature of N

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Soil Test Results

Soil Test Phosphorus (Lbs/Acre)

Rela

tive Y

ield

(%

)

0 20 40 60 80 100 120 140

0

20

40

60

80

100

L M Optimum High

$

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The Soil Test Report

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Figure Credit: UF-IFAS Extension Soil Testing Lab

• Read the whole report!

• No lime recommended

• Recommendations (per 1000 sq. ft)– 2.3 lbs N

– 0.4 lbs P2O5

– 1.4 lbs K2O

Summary

• Soils should be tested prior to applying fertilizers or lime.

• If you are planning to raise your soil pH, have a lime requirement test run.

• Soil samples can be analyzed by the University of Florida – IFAS Extension Soil Testing Lab (or other reputable lab).

• Always read the entire soil test report.13 of 13

©2008 University of Florida-IFAS