Implementing Soil Data Joining and Recorrelation (SDJR) in MLRA Soil Survey Projects.

In the first 100 years of the National Cooperative Soil Survey (NCSS) Program, soil surveys were conducted on a county-by-county basis. State determined priorities, survey standards, and correlation processes were often applied independently. The use of soil survey data and maps was primarily at a local level for local planning and management. Soil survey information originally developed as information pertinent to a specific county is now being used on a larger scale, and data differences related to the product’s vintage are perceived as not joining across political boundaries. Technologies in soil survey evolved significantly over this 100-year period, and surveys of adjacent counties are often separated by years of scientific advancement. Advances in tools for managing and displaying attribute and spatial data have allowed soils data and maps to be stored and manipulated digitally in the National Soil Information System (NASIS). Soil survey data is being used far beyond the scope of the design or intention known at the time of mapping. Sophisticated analysis and modeling techniques using geospatial visualization and operating on state and national scales often highlight the differences in attribute data between adjoining soil surveys. The USDA-NRCS Soil Science Division has positioned its future program by establishing Major Land Resource Area (MLRA) soil survey regional offices and MLRA soil survey field offices. The organization of these offices fosters the update of soils information in a manner that minimizes historical political or regional bias. Update of soils information will be based on typical conditions within the Major Land Resource Area. The Soil Data Joining and Recorrelation (SDJR) Initiative begins the process of bringing attribute data to a common standard through database “harmonization” and identifies future projects that require additional fieldwork. The initiative will result in re-correlated map unit concepts for the MLRA. This approach will minimize the influences of time and county boundaries. The map units with the same and similar names will be evaluated and fully populated. The map units will identify 100 percent map unit composition. New map units will be created where existing documentation identifies a significant change in the map unit concept or soil properties. Soil properties will be evaluated using sound scientific procedures and expert knowledge. Future initiatives will focus on new spatial products and collection of field data necessary to statistically support map unit composition and soil properties where deficiencies are noted during the SDJR Initiative.