SSURGO · SDA · KSSL · Data Model Reference

The Architecture of
American Soil Data

134 tables. 78 foreign-key relationships. One database encoding the physical, chemical, and biological properties of every acre of mapped soil in the United States. This is how it connects.

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Tables
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Relationships
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Columns
88
SDA Live Tables
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Table Groups
Interactive Schema Diagram

The Entity Relationship
Architecture

Force-directed layout of the SSURGO data model. Click any table to explore its columns. Drag to rearrange. Scroll to zoom.

Schema Explorer

Find Any Field
in 2 Keystrokes

Search across all 134 tables and their columns. Click any row to see full field documentation including data type, size, and description from the SSURGO metadata.

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Select a table to view its columns

Live Domain Decoder

Decode Any
Coded Field Value

SSURGO uses coded fields for many categorical values — drainage class, flooding frequency, HSG, soil moisture class. Enter any column name to see all valid domain values and their labels from the live SDA API.

Column or Domain Name
Common domains:
Enter a column name and click Look Up
Related Databases

Beyond SSURGO:
Lab Data & References

SSURGO encodes field-observed soil properties. The NCSS Kellogg Soil Survey Laboratory stores 800,000+ measured samples. Together they form a complete picture of US soil properties.

KSSL · Kellogg Soil Survey Lab
NCSS Lab Data Mart
800,000+ measured soil samples with lab-analyzed pH, CEC, particle size distribution, organic carbon, bulk density, and mineralogy. Includes X-ray diffraction, micromorphology, and water retention data.
📥 Download Lab Data 🔗 Lab Data Mart
Key tables: site · pedon · phorizon · phanalyte
phsample · petaxhistmoistcl · psctotest
pereference · pdinterp · siteobs
SDA · Soil Data Access
Live Query Interface
SDA exposes 88 SSURGO tables via a REST API and interactive query interface. POST SQL to receive JSON or tabular results. The same API powering the Soil Atlas, Regen Ag Map, and SQL Explorer.
▶ Run Queries 📖 Query Help 🔍 SQL Explorer
Endpoint: sdmdataaccess.sc.egov.usda.gov
POST /Tabular/post.rest
Format: JSON+COLUMNNAME · XML · CSV
Schema Documents
Reference Materials
The complete SSURGO schema is documented across multiple official PDFs including table/column descriptions, domain values, relationship diagrams, and aggregation engine specs.
Table & Column Descriptions Relationships Diagram SDA Query Guide
docs/ SDMOnlineSChema.xlsx · SDMOnlineSChema.pdf
SSURGO_Metadata_-_Domains.pdf
TableColumnDescriptionsReport.pdf
SSURGO Schema · Key Chains
The Core Join Path
Every SSURGO query follows the same backbone relationship chain from survey area down to horizon-level properties. Understanding this path unlocks the entire database.
Browse SQL Patterns
legend → lkey
  mapunit → mukey
    component → cokey
      chorizon → chkey
        chtexturegrp · chfrags · chcolor…