This raster describes the inherent, soil productivity of the lower 48 states, as determined by the ordinally based Natural Soil Productivity Index (PI). The PI uses family-level Soil Taxonomy information, i.e., interpretations of taxonomic features or properties that tend to be associated with natural low or high soil productivity, to rank soils from 0 (least productive) to 19 (most productive). The index has wide application, because, unlike competing indexes, it does not require copious amounts of soil data, e.g., pH, organic matter, or CEC, in its derivation. To calculate the PI the following variables were used to guide initial assessments of fertility among the 12 soil orders: (1) organic matter content, (2) CEC, and (3) clay mineralogy, as well as our knowledge of general land use on each of the orders. Next, modifier values were assigned to each suborder, Great Group and subgroup, when these entries implied changes (more, or less) in overall productivity, relative to the base value. Lastly, the PI was modified by adjusting for texture, based on texture family classification. Its derivation is based on soil taxonomic information, normally available in soil digital datasets. The index has many applications in the geosciences, forestry, ecology, geography, environmental modeling, and policy development, especially when examined spatially. The Productivity Index was developed by a partnership between Michigan State University and the U.S. Forest Service. PI values for all soils currently classified by the NRCS can be accessed from the PI website: http://foresthealth.fs.usda.gov/soils.
Citation: Schaetzl, R.J. Krist, F.J. Jr., and B.A. Miller. 2012. A Taxonomically Based, Ordinal Estimate of Soil Productivity for Landscape-Scale Analyses. Soil Science 177:288-299.