Soil sampling and tests
Contents
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There are hundreds of soil tests that can be conducted, both in the field or laboratory. This page provides an overview of more common soil tests, links to information on sampling, and links to test methods.
Sample collection
Soil sample collection methods vary and covering all acceptable methods is beyond the scope of this page. Below are links to sampling methods, including videos.
Sampling for chemical tests
Note that these references provide information on soil sample collection. Except where noted, they do not include field procedures associated with specific tests and most do not include information on quality assurance and quality control (QA/QC). Use professional, certified/licensed individuals or firms to ensure appropriate QA/QC procedures are followed.
Documents
- US EPA - focus on VOCs and PFAS
- Testing Your Soil Why and How to Take a Soil-Test Sample - University of Hawaii
- Sampling Soils for Nutrient Management - USDA-NRCS; focus on phosphorus
- Procedure for taking soil samples - Stephen F. Austin State University
- Guidelines for Soil Sampling - USDA-NRCS
- Soil Sampling Guidelines - Purdue University
- Composite Soil Sampling - MCSE - Kellogg Biological Station
- Soil sample collection and analysis procedures - MPCA Petroleum Remediation Program
- Quality Assurance Project Plan Midland Area Soil Sampling, Midland Michigan
- Soil Sampling Quality Assurance User's Guide - US EPA
Videos of sample collection for lab analysis
- How to Collect a Soil Sample for Lab Analysis
- Collecting Soil Samples: Part 1 - Tools, Part 2 - Sample collection
- How to Take a Soil Sample
Laboratory tests
Below is a list of recommended laboratory tests
Nutrients
Soil macronutrients include phosphorus, nitrogen, potassium, sulfur, calcium, and magnesium. Phosphorus is an important pollutant of concern in surface water, particularly lakes. Though there are several forms of phosphorus, they can roughly be divided into dissolved phosphorus and particulate phosphorus, with dissolved phosphorus being much more bioavailable than particulate forms. Dissolved phosphorus is typically identified as phosphorus passing through a 0.45 micron filter. For a detailed discussion of phosphorus, link here.
Nitrogen is also an important nutrient in both surface water and groundwater. Nitrogen concentrations in stormwater are typically below levels of concern for receiving waters.
Potassium, sulfur, calcium, and magnesium are typically not pollutants of concern in stormwater runoff, but they may be deficient in some soils and therefore potentially impact vegetation.
- Phosphorus
- Bray Method: use on acidic and neutral soils
- Olsen Method: preferred on high pH soils
- Mehlich-3 Method: provides a better indicator of plant-available phosphorus
- Nitrogen
- Potassium, Sodium, Calcium, Magnesium, Boron and sulfate-Sulfur
- Inductively Coupled Plasma Emission Spectrometry (ICP-AES) - recommended due to lower detection limits
- atomic absorption spectroscopy
Metals
- Inductively Coupled Plasma Emission Spectrometry (ICP-AES) - recommended due to lower detection limits
- atomic absorption spectroscopy
pH
- Saturated paste - recommended
- 1:1 and 2:1 water ratios
Organic matter and carbon
- organic carbon combustion
- organic matter Walkley-Black
- Organic matter loss on ignition - recommended due to ease of use and since organic matter is more commonly used compared to organic carbon
Exchange capacity
- Cation exchange capacity - multiple methods are available for cation exchange capacity. For more information read here.
- Barium chloride Compulsive Exchange Method - recommended but is time consuming and generates a hazardous waste
- Ammonium Acetate Method - acceptable if soil pH is near 7.0
- Agronomic Soil Tests - estimates CEC from test extractable Ca, K, and Mg and some rapid measure of exchangeable acidity (see next bullet)
- Exchangeable Potassium, Calcium, Magnesium, Sodium And Estimated Cation Exchange Capacity
Field methods
- Soil water (moisture) content
- Electrical-resistance
- Heat-diffusion
- Absorption
- Tensiometric
- Penetration
- Radioactive
Soil physical and hydraulic measurements
Bulk density
Soil bulk density is an important measurement for determining soil infiltration and plant rooting properties. Measuring bulk density involves proper sample collection and laboratory analysis. Below are links to videos demonstrating methods for collecting bulk density samples.
- Bulk density and soil water (moisture) content - a 12 minute video illustrating how to collect the sample in field and measure in the lab using the core method
- Bulk density and soil water (moisture) content - a 10 minute video using the core method
- Bulk density and soil water (moisture) content - this 34 minute video describes the clod method, which is preferred but more time consuming and cannot be used for soils where intact clods cannot be collected
Infiltration rate
Infiltration rates should be measured in the field. This page provides information on measuring soil infiltration rates.