Soil Analyses

Note: This is a verbatim reproduction of SWAT lab analysis methods previously posted on the SWAT webpage prior to lab closure.

Archive of NMSU SWAT Lab References for Soil Analyses

Test Procedure Reference
Standard Soil Test
Organic Matter Walkley - Black 6
pH Saturated Paste 2
Salts Solution conductivity 2
Phosphorus Olsen 3 & 7
ESP SAR Estimation 2
Texture By Feel 10
Potassium (K) ICP, 1:5 H2O Extract 1
Nitrate – Nitrogen (NO3) Cadmium Reduction Column 3 & 4
Fertility Tests
Phosphorus Olsen 3 & 7
Nitrate Cd Reduction, 1:5 H2O Extract 4
Potassium 1:5 NH4OAc Extract 3
Nitrogen Kjeldahl 5
Fe, Zn, Cu, and Mn DPTA Extract 3
Organic Matter Walkley - Black 5
Boron Hot Water Soluble 5
Soil Characterization Tests
pH Choice of Procedure 8
E.C. of saturated extract Solution conductivity 2
% H2O at saturation Drying at 110 +/−5 degrees C 12
CaCO3 (equivalent) Rapid titration 5
Gypsum Acetone Precipitation 8
Mechanical Analysis Hydrometer 8
Mechanical Analysis Pipet 8
Extractable Cations NH4OAc at pH 7 or 9 8
Exchangeable Cations NH4OAc extractable minus soluble 8
Cation Exchange Capacity Na saturated then NH4OAc extracted 5
Extractable Hydrogen BaCl2 – TEA Extraction 8
Extractable NH4 2N KCl (colorimetric) 5
Soluble Ions From Saturated Paste Extract
Saturated paste Deionized H2O 2
Soluble cations ICP-ES 4
Chloride Colorimetric 4
CO3 + HCO3 Titration 4
Soluble Sulfate Turbidimetric 4
Soluble Ammonium Colorimetric 4
Soluble Boron ICP 4
Metals ICP 4
Grinding Soils Stainless Steel Grinders  
Extractable Arsenic NaHCO3 extract 11
Extractable Selenium Hot Water reflux 5
Microwave digest EPA method 3015 9


1. Cihacek, L. J. 1983. Interpreting Soil Analysis. Cooperative Extension Service Guide A-126. New Mexico State University Publ. Office, Las Cruces, NM.

2. USDA Staff. 1954. Diagnosis and Improvement of Saline and Alkaline Soils. USDA Agric. Handb. 60. L.A. Richards (ed.) U.S. Gov. Print. Office, Washington, D.C.

3. Ludwick, A.E. and J.O. Reuss. 1974. Guide to Fertilizer Recommendations in Colorado. Colorado State University, Fort Collins, Colorado. (And personal communications with Albert E. Ludwick).

4. U.S. Environmental Protection Agency. 1979. Methods for Chemical Analysis of Water and Wastes. U.S. Gov. Print. Office, Washington, D.C.

5. Agronomy Society of America. 1965. Methods of Soil Analysis. Part 2. Chemical and Microbiological Properties. C.A. Black (ed.) Agronomy 9, Madison, WI.

6. Agronomy Society of America. 1982. Methods of Soil Analysis. Part 2. Chemical and Microbiological Properties, A.L. Page (ed.) 2nd Ed. Agronomy 9, Madison, WI.

7. Olsen, Sterling R., C. V. Cole, Frank S. Watanabe, and L.A. Dean. 1954. Estimation of Available Phosphorus in Soils by Extraction With Sodium Bicarbonate, USDA Circular No. 939, U.S. Gov. Print. Office, Washington, D.C.

8. USDA-SCS Staff. 1972. Soil Survey Laboratory Methods and Procedures for Collecting Soil Samples. 1972. U.S. Gov. Print. Office, Washington, D.C.

9. U.S. Environmental Protection Agency, 1986. Test Methods for Evaluating Solid Waste USEPA Rep. SW-846, 3rd Ed., 1B. Laboratory Manual, Physical/Chemical Methods.

10. Thein, S. J. 1979. A Flow Diagram for Teaching Texture-by-feel Analysis, J. Agron. Education. 8: 54-55.

11. Wollson, E. A., J. H. Axley, and P. C. Kearney. 1971. Correlation Between Available Soil Arsenic, Estimated by Six Methods, and Response of Com (Zea mays L.), Soil Sci. Soc. Amer. P. 35: 101-105.

12. American Society of Testing and Materials. 1996. Standard Test Method for Laboratory Determination of Water (Moisture) Content of Soil and Rock, Rep. D2216-92. In Annual Book of ASTM Standards 4.08:185-188.