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
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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
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