Public and Private Labs Soil Test Methodology and Recommendations Comparisons and Contrasts

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Public and Private LabsSoil Test Methodology
and RecommendationsComparisons and Contrasts
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Lab differences and similarities are best
illustrated by comparing exchange sample results.
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Preparations for Soil Exchange

• Bulk sample is air dried
• Grinding
• Mixing
• Partitioned with attention to particle settling

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Compare to Splitting Samples in the Field !

• Nutrients not uniform
• Cant properly mix sample
• Results will likely differ even if analyzed by
  the same lab

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Soil Test Labs Use Different Extractants

• Mehlich 1
• AL, FL, TN, VA, GA, SC Private
• Mehlich 3
• KY NC
• Bray-1
• Outside the Southeast

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Reporting Exchange Results

• Data are converted to same units (mg/dm3)
• Data are grouped by extractants

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Mid-Atlantic Soil Test Plant Analysis Workgroup

• Public Labs
• Clemson University
• North Carolina Dept. of Agriculture
• Penn State
• University of Delaware
• University of Georgia
• University of Maryland
• Virginia Polytechnic Institute
• West Virginia University

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Mid-Atlantic Soil Test Plant Analysis Workgroup

• Private Labs
• A L Richmond, VA
• Agri-Analysis Leola, PA
• Brookside New Knoxville, OH
• Countrymark Indianapolis, IN
• Na-Churs Marion, OH
• Spectrum Washington C.H., OH

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Soil pH - 1999 MASTWG
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Soil P - 1999 MASTWG
Clemson, Georgia, Delaware, Maryland and Virginia
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Soil K - 1999 MASTWG
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Soil Mg - 1999 MASTWG
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SC and GA Rating SystemsPotassium (Coastal Plain)
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MASTWG also exchangesplant tissue andmanure
samples
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North American Proficiency Testing program

• Over 150 labs participate
• Samples submitted quarterly

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Lab Differences

• Methodology, e.g., extractants
• Modifications of standard methods
• Rating systems
• Recommendations
• Philosophy
• Region
• Use of quality control

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Lab Similarities

• Use of standard methodology
• Desire for credibility

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Recommendations

• Stick to one lab
• Develop long-term relationship
• Know their procedures
• Request samples be retested if there is any
  question
• Be aware of problems with splitting samples
  between labs

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Final Questions