Soil Analysis for Researchers

Researchers come to the Soil Testing Lab for an in depth analysis of their soil tailored to their needs. Soil samples are transferred to sterile, labeled containers and dried in a forced air oven (unless analysis prohibits immediate oven drying). Once dry, they are ground with a pulverizing-type grinder and analyzed. When the data is complete and has been reviewed, sample data is emailed to the researcher or producer. Samples may then be returned upon request.

Soil Preparation

Soil is prepared by drying overnight in a 60°C oven, then grinding to pass through a 2mm sieve. When iron is to be analyzed, samples are air-dried to prevent incorrectly high values. When nitrogen is to be analyzed, samples are dried as soon as possible to prevent bacterial conversion of nitrogen.

Soil Sample Collection

Sample collection will vary depending on the experiement being conducted. Please label all samples and completely fill out the sample information sheets so lab analysis and processing can occur efficiently.

Forms

For State of Kansas Research Agencies:

• Scooped Soil Sample Information & Order Sheet (pdf)
• Weighed Soil Sample Information & Order Sheet (pdf)

For External Research Agencies:

• Scooped Soil Sample Information & Order Sheet (pdf)
• Weighed Soil Sample Information & Order Sheet (pdf)

 

Available Tests for Researchers

pH

pH is measured directly using a 1:1 slurry of 10 g of prepared soil with deionized water with an automated system.Buffer pH for lime requirement is measured with the SMP buffer technique. Lime recommendations are reported in lbs of effective CaCO3 per acre.

Phosphorus

Melich III Phosphorus

This P analysis uses a universal extractant that removes a wide range of elements. It is used by many laboratories for multiple-element analysis.It also requires 2 g of prepared soil.

Bray Phosphorus

The Bray P test is used for extractable (potentially plant available) phosphorus in soil because of its consistent correlation with yields from fertilizer recommendations generated from the test results. It utilizes an HCl-ammonium fluoride extractant and a colorimetric assay that requires 2 g of prepared soil.

Olsen Phosphorus

When the soil sample is calcareous, above pH 7.5, and the Bray P value is low, the Olsen P test is recommended. It makes use of a sodium bicarbonate extractant, a colorimetric assay, and 2 g of prepared soil.

Cations

Exchangable Cations

The four cations Ca ²⁺ , Mg ²⁺ , K ⁺ , Na ⁺ are extracted with 1 M ammonium acetate, pH 7.0. Analysis is by Flame Atomic Absorption or ICP Spectrometry.The test requires 2 g of prepared soil and only one extraction fee is charged for each sample.

Cation Exchange Capacity

The displacement method with saturating ammonium acetate is used to measure the cation exchange capacity contained in a 2-g sample. After washing and elution, the NH ₄ ⁺ released is determined by the colorimetric assay used for KCl extracts.

DTPA Extraction

The micronutrients Cu ⁺ , Fe ³⁺ , Mn ²⁺ , Zn ⁺ are extracted with the chelator DTPA and analyzed by Flame Atomic Absorption or ICP spectrometry.The test requires 10 g of prepared soil and only one extraction fee is charged for each sample.

Nitrogen

Both inorganic nitrogen forms, NH ₄ ⁺ and NO ₃ ^- , are extracted with 1 M KCl, using 2 g of prepared soil. Cadmium reduction is used for nitrate and colorimetric procedures are run in separate channels in a flow analyzer to measure these ions simultaneously.

Soluble Salts

The conductivity of a saturated paste water extract is determined with a digital conductivity meter.The value in mmhos/cm is an measure of the total soluble salts in the sample.The saturated paste requires 50 g of prepared soil.

Salt Alkali

This complete analysis of the saline and sodic properties of the soil sample includes the soluble salts measurement, soluble, extractable, and exchangeable sodium levels, pH, and classification of the soil for the sodium and sodium chloride risk. This test requires 50 g of prepared soil.

Texture

Using sodium hexametaphosphate as a dispersing agent, the sand, silt, and clay fractions of the sample are estimated with the hydrometer method. Fifty grams of prepared soil are needed.

Chloride

Soil chloride is extracted from a 10g sample with calcium nitrate and analyzed with the Mercury Thiocyanate colorimetric method.

Sulfate

A monocalcium phosphate extraction of sulfate from 10 g of soil is analyzed on a flow analyzer by the turbidimetric mehod. Values are reported as elemental sulfur.

Aluminum

Extraction with 1 M KCl and analysis by ICP Spectrometry gives soil levels of Al 3 + . This test is recommended for samples with pH of 5.5 or below and requires 5 g of prepared soil.

Total Carbon & Nitrogen

A LECO TruSpec CN combustion analyzer reports total levels (inorganic and organic) of C and N on a weight percent basis. A 0.35g sample of prepared soil is normally used.

Total Nitrogen & Phosphorus

A modified Kjeldahl digestion is performed on 1 g of prepared soil. The diluted digest is analyzed for nitrogen and phosphorous in separate colorimetric reactions using a flow analyzer.

Organic Matter

Loss on Ignition

Modified version of:

Combs, S.M and M.V. Nathan. 1998. Soil organic matter. In: recommended chemical soil test procedures for the north central region. Missouri Ag. Exp. Stn. SB 1001. Colombia, MO. P. 53 – 58.

The modifications being 1 g of soil used, drying at 150 for 2 hours, and igniting at 400 for 3 hours.

Note: Many of the original methods used for the above tests may be found in the following reference: 1998. Recommended Chemical Soil Test Procedures for the North Central Region North Central Regional Publication No. 221(Revised). University of Missouri Agricultural Experiment Station, Columbia, MO.