Use of Soil Survey Mapping and Sampling for Determining Geochemistry of Regions

Abstract

The U.S. National Cooperative Soil Survey (NCSS) information about geographic distribution of soils is based on landforms and soil‐forming factors. A recent effort was initiated to determine the geochemistry of soils that are sampled as part of the routine NCSS work. The objectives of this article are to describe the mapping and site selection procedures, utility of these procedures in the geochemical analysis of soils, and the work and future direction of the Soil Geochemistry Program that was developed for this effort. This program was created within the U.S. Department of Agriculture, Natural Resources Conservation Service (USDA‐NRCS), for the purposes of instituting and monitoring the quality of laboratory geochemical methods and data, investigating the distribution of natural elemental concentrations in soils, and providing leadership in the application of geochemical data for NRCS. The soil survey has typically used the representative pedon concept as a basis for site selection, determined from the evaluation of soil morphology and component landforms within mapping units. The intent of this concept is to extend limited point data to geographic coverage. A geospatial database was compiled, containing major and trace element data for selected NCSS pedons. These data are provided with depth for major diagnostic horizons. Although initial geochemistry efforts have concentrated on benchmark soils to facilitate evaluation of source factors and broaden the utility of the data, this dataset includes both anthropogenic and nonanthropogenic soils. Future efforts require the investigation of geochemical variability of mapping units and the pedogenic redistribution of trace elements within soil landscapes.

Keywords:

• Major and trace elements
• mapping units
• pedology
• soil geochemistry
• soil survey