href="#ulink_c314fc56-5627-5268-9f66-4176d399d22a">Table 1.2 Tier 2 Soil Health Indicators and Methods to be Assessed
| Indicator | Method | Reference |
|---|---|---|
| Sodium Adsorption Ratio (SAR) | Saturated paste extract followed by atomic absorption or inductively coupled plasma spectroscopy | Miller et al., 2013 |
| Soil Stability Index | Combination of wet and dry sieving at multiple sieve sizes | Franzluebbers et al., 2000 |
| Active Carbon | Permanganate oxidizable carbon (POXC). Digestion followed by colorimetric measurement | Weil et al., 2003 |
| Soil Protein Index | Autoclaved citrate extractable | Schindelbeck et al., 2016 |
| B‐Glucosidase | Assay incubation followed by colorimetric measurement | Tabatabai, 1994 |
| N‐acetyl‐B‐D‐glucosaminidase | Assay incubation followed by colorimetric measurement | Deng and Popova, 2011 |
| Phosphomonoesterase | Assay incubation followed by colorimetric measurement | Acosta‐Martínez and Tabatabai, 2011 |
| Arylsulfatase | Assay incubation followed by colorimetric measurement | Klose et al., 2011 |
| Phospholipid Fatty Acid (PLFA) | Bligh‐Dyer extractant, solid phase extraction, transesterification; gas chromatography | Buyer and Sasser, 2012 |
| Genomics | 18S, 16S or ITS analysis or a combination of 16S and 18S/ITS and/or shotgun metagenomics | Earth Microbiome Project 500; Marotz et al., 2017 Thompson et al., 2017 |
| Reflectance | Diffuse reflectance spectroscopy | Veum et al., 2015 |
Several layers of certifications or validations may be in place to ensure data quality for commercial analytical labs. For example, the Agricultural Laboratory Proficiency (ALP) Program provides soil samples to laboratories for analysis and then assesses that laboratory’s results relative to the test soil’s known properties. In turn, the ALP program is accredited by the American National Standards Institute/American Society of Quality Control National Accrediting Board (ANAB) through testing of ISO/IEC 17043, itself an international standard of the International Organization for Standardization and the International Electrotechnical Commission for laboratory proficiency testing that determines the performance of individual laboratories for specific tests or measurements and is used to monitor laboratories’ continuing performance through interlaboratory comparisons. Thus, commercial laboratories conducting analyses for soil health indicators select measurements and indicators that are understood in the research community to relate to processes in soil important to soil health; and methods that are affordable to the farming community, as well as verifiable for accuracy and precision (= reliability to the producer) by independent tests.
Summary and Conclusions
This introduction to Volume II provides those interested in soil health assessment methods a brief background regarding identification and selection of the indicators within this volume and to provide context regarding current and future soil health assessment efforts. It also demonstrates that multiple groups (i.e., SHI and the NRCS‐SHD) that engaged in workshops and conferences during 2013 to 2015 continue to coordinate soil health assessments to protect and enhance our fragile, yet life‐sustaining soil resource for current and future generations.
References
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15 Kemper,
