Laboratory Information Manual Preface

For any measurement program that collects analytical data over a long period of time for comparative purposes, the quality and credibility of those data are critical (Taylor, 1988). It is equally critical that the data can be easily understood by the user. The uses of these data include, but are not limited to, routine soil characterization, special analyses, soil classification, interpretations, and soil genesis and geomorphology studies. Because of the diverse uses of these data, it follows that pedon characterization data, or any soil survey data, are more appropriately used when the operations for collection, analysis, and reporting of these data are well understood. Results differ when different methods are used, even though these methods may carry the same name or concept. Comparison of one bit of data with another is difficult without knowing how both bits were gathered. As a result, operational definitions have been developed and are linked to specific methods. Soil Taxonomy (Soil Survey Staff, 1999) is based almost entirely on criteria that are defined operationally, e.g., standard particle-size analysis. When Soil Taxonomy (Soil Survey Staff, 1975) was written, the authors knew that no conceptual definition of clay could be approximated in all soils by any feasible combination of laboratory analyses. Hence, instead of defining clay, the authors defined the operations to test the validity of a clay measurement and a default type of operation for those situations in which the clay measurement was not valid. The operational definition helps to describe a soil property in terms of operations used to measure it. This document, the Soil Survey Laboratory Information Manual, Soil Survey Investigations Report (SSIR) No. 45, discusses operational and conceptual definitions of Soil Survey Laboratory (SSL) procedures.

The purpose of this manual is to serve as a standard reference in the use and application of SSL characterization data. The manual is intended to help maximize user understanding of these data. Even though it presents descriptive terms or interpretive classes commonly associated with ranges of some data elements, this document is not intended to be an interpretive guide.

This manual serves as a companion manual to the Soil Survey Laboratory Methods Manual, Soil Survey Investigations Report No. 42 (Soil Survey Staff, 2004), and the Soil Survey Field and Laboratory Methods Manual, Soil Survey Investigations Report No. 51 (Soil Survey Staff, 2009). SSIR No. 42 documents the methodology and serves as a reference for the laboratory analyst, whereas SSIR No. 51 serves as a reference for the scientist in a field or field-office setting. The documentation of standard operating procedures (SOPs) ensures continuity in the analytical process. Both SSIR No. 42 and SSIR No. 51 are “how to” manuals; their respective described methods follow the same format and cover many of the same kinds of analyses. The Soil Survey Laboratory Information Manual (SSIR No. 45) follows the same topical outline as the Soil Survey Laboratory Methods Manual (Soil Survey Staff, 2004). SSIR No. 45 provides brief summaries of the SSL methods as well as detailed discussion of the use and application of the resulting data.

This manual serves to document the historical background of the development of many SSL methods. It is important to document this background, as methods development in soil characterization has been instrumental in developing principles and understanding of the nature and behavior of a wide range of soils. It is expected that this manual will evolve over time as new methods based on new knowledge or technologies are developed and applied. It is also expected that the scope of this manual will change over time. Currently, the scope of this document includes such diverse uses as soil survey, salinity, fertility, and soil quality. With the continued development of and modification to the database derived from these diverse data, it is expected that more discipline-dedicated manuals will be developed and enhanced.

This manual is divided into four major parts: Introduction, Primary Characterization Data, Supplementary Characterization Data, and the Appendices. The introduction describes general pedon information that appears on both the Primary Characterization Data Sheets and the Supplementary Characterization Data Sheets. This general information is important nonanalytical metadata. Also described in the introduction are the “Pedon Calculations” that appear on the Primary Characterization Data Sheet.

Primary data are those data that appear on the SSL data reports entitled Primary Characterization and are based primarily on analytical data. Rather than following the SSL data sheet format, the discussion of the primary data follows the discussion format presented in SSIR No. 42 (Soil Survey Staff, 2004); that is, it presents broad categories of characterization data. Method codes are not embedded in the descriptions of the primary data but are cross-referenced by method code in the table of contents in this manual. The discussion is logically and sequentially presented as follows: (1) field procedures for site and pedon description and sampling and (2) laboratory procedures used to characterize the physical, chemical, biological, and mineralogical properties of a soil and to characterize water and plant samples. The field component of this manual provides information on the rationale of the SSL field procedures. Key considerations and procedures related to site selection, geomorphology, and pedon, water, and biological sampling are discussed. Within the aforementioned categories (physical, chemical, biological, and mineralogical) of the laboratory component of this manual is discussion of specific soil properties (e.g., structure, pH, biomass, and clay mineralogy) that are commonly measured for soil survey and are indicative of soil processes. Important references related to these topics include, but are not limited to, the Soil Survey Manual (Soil Survey Division Staff, 1993), the Field Book for Describing and Sampling Soils (Schoeneberger et al., 2002), Soil Taxonomy (Soil Survey Staff, 1999), and peer-recognized literature (e.g., Soil Science Society of America monographs).

Supplementary data are those data that appear on the SSL data reports entitled Supplementary Characterization. These data are considered the interpretive physical data for pedons analyzed at the SSL. They are primarily derived or calculated data, using the analytical data as a basis for calculation. Unlike the primary data, the supplementary data are not discussed in SSIR No. 42 (Soil Survey Staff, 2004) and thus do not carry method codes.

The Appendices consist of example pedon data sheets, including the primary, supplementary, and taxonomy sheets as well as grain-size distribution curves and water retention curves for selected pedons. These data sheets are used in a number of example pedon calculations presented throughout this manual, such as weight to volume conversions, weighted averages, and other estimates. These examples are intended to improve the ability of users of SSL data to understand and apply these data.

Rebecca Burt, Editor
Research Soil Scientist
National Soil Survey Center
United States Department of Agriculture
Natural Resources Conservation Service
Lincoln, Nebraska

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