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Test Methods & Procedures

When comparing results from one laboratory to the next it is important to determine the following:

  1. Laboratory method used for each analysis.
  2. Units reported for each analysis.
  3. Any conversion or calculation used for specific tests.

It is important to note that there is no perfect method for determining how much or little of an essential nutrient is available for plant uptake. Availability is affected by: soil moisture, temperature, soil pH, clay/organic matter content, soil drainage, physical barriers and many other factors. As these factors change the availability of nutrients also change. What a soil test measures is the degree of fertility; be it low, medium or high.

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Analysis

Units

Method Description

SOIL ANALYSIS

Soil pH

N/A

1:1 Soil/Water Slurry

Soluble Salt

mmhos/cm

1:1 Soil/Water Slurry

Buffer pH

N/A

Sikora Buffer Solution

Cations:  Ca-Mg-K-Na

ppm

Ammonium Acetate Extraction

Phosphorus
     If pH < 7.2
     If pH > 7.1


ppm
ppm


Bray I Extraction
Olson Extraction

Traces:  Zn-Mn-Fe-Cu

ppm

DTPA Extraction

Sulfur

ppm

Monocalcium Phosphate (ICP Determination)

Boron

ppm

Hot Water Extraction (ICP Determination)

Nitrate-N

ppm

Cadmium Reduction

Particle Size Analysis
(Sand-Slid-Clay)

%

Hydrometer Measurement

Salinity Evaluation

mmhos/cm

Saturated Paste Extraction

Other Methods Available

 

Pertains to country of origin

Extractable Soil Ammonium 

ppm

KCI extraction 

Extractable Chloride in Soil

ppm

Calcium Nitrate Extraction

Soil Moisture

%

Loss of Drying

Organic Matter

%

Loss of Ignition

Extractable Aluminum

ppm

Cesium Chloride Extraction

Extractable Molybdenum

ppm

Ammonium Oxolate

 

 

 

PLANT ANALYSIS

Nitrate-Nitrogen

ppm

2% Acetic Acid digestion

Phosphate-Phosphorus

ppm

2% Acetic Acid digestion

Extractable Potassium

%

2% Acetic Acid digestion

Total Nitrogen

%

Kjeldahl Digestion

Total Phosphorus

%

Nitric Acid/Hydrogen Peroxide Digestion

Plant Minerals

% and ppm

Nitric Acid/Hydrogen Peroxide Digestion

 

 

 

GREENHOUSE MEDIA TESTING

Media pH

N/A

Saturated Media Extract (SMS)

Electrical Conductivity

mmhos/cm

                     "

Phosphorus

ppm

                     " 

Potassium

   "

                     " 

Calcium

   "

                     " 

Magnesium

   "

                     " 

Sodium

   "

                     " 

Zinc

   "

                     " 

Manganese

   "

                     " 

Copper

   "

                     " 

Iron

   "

                     "

Boron

   "

                     "

Aluminum

   "

                     "

Nitrate-N

   "

                     "

Ammonium-N

   "

                     "

Extractable
     Zinc
     Manganese
     Copper
     Iron


ppm
  "
  "
  "


DTPA Extraction
           "
           "
           "

Organic Matter &
Organic Carbon

%

Loss on Ignition

Total Nitrogen

%

Kjeldahl Digestion

Soluble P205

%

Citric Acid Digestion

Soluble K20

%

Ammonium Oxalate

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  • Analytic procedures used in US EPA Report SW-846, Test Methods for Evaluating Soil Waste, 3rd Edition, November 1990, as revised.
  • Association of Official Analytical Chemists (AOAC) Official Methods of Analysis, 1990, 15th Edition.
  • Methods of Soil Analysis, Parts I, II, and III. Soil Science Society of American. 1996.
  • North Central Regional (NCR) Publication No. 221 (Revised).  Recommended Chemical Procedures for the North Central Region Bulletin No. 499 (Revised) October 1988.
  • Standard Methods for the Examination of Water and Wastewater, 18th Edition, 1992.
  • The American Society for Testing and Materials (ASTM) Standard Tests Methods, 1988.