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TEST PROCEDURES & METHODS

For the best use of soil testing results, it is important to know the following:

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

Actual nutrient availability in the soil is determined by changing factors including: soil moisture, temperature, pH, clay content, internal drainage, organic contact and physical barriers. As any of these factors change, the availability will also change.

For a printable PDF with all methods, click here.

SOIL

- All soil samples are dried and ground.

Analysis

Units

Method Description

Soil pH

--

1:1 Soil/Water Slurry

Buffer pH (Buffer Index)

--

Sikora Buffer Method

Soluble Salts (EC)

mmhos/cm

1:2 Soil/Water Slurry

Potassium

ppm

Bray 1 Extraction

Phosphorus, Bray 1

ppm

Bray 1 Extraction

By request:

 

 

      Phosphorus, Bray 2

ppm

Bray 2 Extraction

      Phosphorus, Olsen

ppm

Olsen Extraction, when soil pH >7.2

Calcium, Magnesium and Sodium

ppm

Ammonium Acetate Extraction

Sulfur

ppm

Monocalcium Phosphate Extraction

Copper, Iron, Manganese and Zinc

ppm

DTPA Extraction

Boron

ppm

Hot Water Extraction

Nitrate-Nitrogen

ppm 

KCl Extraction, Cadmium Reduction

Organic Matter

%

Loss on Ignition (LOI), expressed as OM%



 

Soil test methods are described in:

  • Nutrient Application Guidelines for Field, Vegetable, and Fruit crops In Wisconsin, 2012 Publication A2809
  • Wisconsin Soil Testing and Plant Analysis Procedure, No. 6 Fertility Series 1970, Revised 1976.
  • Recommended Chemical Soil Test Procedures for the North Central Region, North Central Research Publication No. 221 (Revised), 2015, Missouri Agricultural Experiment Station SB 1001.

 

PLANT TISSUE

- All plant tissue samples are dried and ground.

Analysis

Units

Method Description

Total Nitrogen

%

Total Kjeldahl Digestion

Minerals:

 

 

     P, K, S, Ca, Mg, Na

%

Nitric Acid Digestion

     Cu, Fe, Mn, Zn, B, Al

ppm

Nitric Acid Digestion

Plant tissue test methods are described in:

  • Wisconsin Soil Testing and Plant Analysis Procedure, No. 6 Fertility Series 1970, Revised 1976.    
                 

MANURE

- All samples are handled and reported as detailed below.

Analysis

Units

Method Description

Dry Matter/ Moisture

%

Oven Drying at 50°C, 48 hours

Nitrogen (TKN)

%

Total Kjeldahl Digestion, “As Received”

Minerals:

 

 

     P, K, S, Ca, Mg, Na

%

Nitric Acid Digestions, “Dry Basis”

     Cu, Fe, Mn, Zn

ppm

Nitric Acid Digestions, “Dry Basis”

Ammonium-Nitrogen

%

KCl Extraction, “As Received”

Nitrate-Nitrogen

%

KCl Extraction, “As Received”

Organic Nitrogen

%

Calculated: (TKN – Ammonium-Nitrogen)

pH

--

1:2 Manure:Water Slurry, “As Received”

Electrical Conductivity (EC)

mmhos/cm

1:2 Manure:Water Slurry, “As Received”

 

 Manure test methods are described in:

  • Nutrient Application Guidelines for Field, Vegetable, and Fruit crops In Wisconsin, 2012 Publication A2809
  • Recommended Methods of Manure Analysis. 2003, University of Wisconsin Extension Publication A3769