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Why are the soils (mapped) on my property changing?


Soils NRCS-Maine

 

 

If you are a frequent user of the Web Soil Survey you may notice changes that have occurred on an area of interest from what it was a few years ago.  For instance, your property may have been mapped as soil series A but now it is mapped soil series B, but the map unit symbol has not changed.  Certainly this must be a mistake, right?  Not necessarily.  For the past five years NRCS has been working to tighten up discrepancies that exist in soil series across the country and fix outdated or obsolete data.  The project is known as the Soil Data Join Recorrelation (SDJR) project.
 

WHAT IS THE PURPOSE OF THE SDJR INITIATIVE?

Phase 1 of the SDJR Initiative focuses on the attribute database known as the National Soil Information System (NASIS).  All soil map units that exist within a Major Land Resource Area (MLRA), which are large units of land that have similar uses in management and land use, with a similar name and slope range will be combined into new map units with consistent data across county and state lines.  Phase 1 is about 90 percent complete.

Phase 2 will focus on improvements in the spatial data, and will begin in the next two years. This is an exciting prospect because imagery, elevation data, and other resource inventory tools and techniques have been advancing rapidly. That presents tremendous potential for efficient and significant improvement in soil survey spatial data in years to come.
 

BACKGROUND BEHIND THE SDJR INITIATIVE:

In the first 100 years of the National Cooperative Soil Survey (NCSS) Program, soil surveys were conducted county by county on the basis of State priorities and applied statewide and regional guidance documents and correlation processes. The use of soil survey data and maps was primarily at a local level for planning management. Technologies in soil survey evolved significantly over this 100-year period, and surveys of adjacent counties were often separated by years of scientific advancement. But those data and maps are now being used on a larger scale across soil survey area boundaries. SDJR work removes old inconsistencies in data for soil series across local and state boundaries. SDJR work also involves the process of bringing soil data to a common standard and identifies future projects that require additional fieldwork.


WHAT ARE SOME CHANGES I MIGHT SEE?

Highlighted in the opening paragraph was an example of the soil on a piece of land changing from soil A to soil B.  How is it that the soil series itself might change on a piece of property?  Typically, the soil itself has not changed, but modern standards for interpreting the data warranted a change to the soil map information.  Prior to SDJR, many soils were dual drainage, meaning they had a wide range for depth to seasonal high water table information.  A major focus of SDJR changes is to improve older soil surveys by eliminating dual drainage soils.  In order to accomplish this goal, some new soil series have been developed to represent a single drainage class within a catena. 

For example: the Buxton Series which occurs in many older vintage soil surveys was somewhat poorly to moderately-well drained which spans from 20 centimeters to 100 centimeters deep to a seasonal high water table.  A new series called Lamoine was established to cover the somewhat-poorly drained portion of this map unit (20-40cm). Buxton was revised to be only moderately well-drained.

New and existing field observations, historical knowledge, and professional judgment were then used to determine which existing map units and slope phases would be recorrelated to which series. 

Other changes that may occur include, but are not limited to: Soil interpretation changes, changes from historic Hydrologic Soil Group ratings, and map unit slope phases. While we regret any difficulties that these changes may present, we are doing our best to improve and modernize our soil survey products overall.

Finally, remember that soil surveys are not substitutes for on-site investigations by professional soil scientists and site evaluators, who should be consulted prior to important land use decisions.
 

Questions:

If you have specific questions about the SDJR Initiative or any soil survey related questions please contact Nick Butler at the Dover Foxcroft Soil Survey Office located at 42 Engdahl Drive, Dover-Foxcroft, ME 04426.

Phone: (207) 564-2321 x 103
Email: Nicholas.butler@me.usda.gov