USDA Soil Data Access¶
| Field | Current catalog entry |
|---|---|
| Provider | Soil Data Access (SDA), exposing Soil Data Mart content |
| Organization | USDA Natural Resources Conservation Service |
| Coverage | Published U.S. soil survey data and territories represented in Soil Data Mart |
| Data type | Query interface to survey tabular/spatial data, not a separate observation database |
| Properties | Determined by SSURGO/STATSGO2 tables and published survey content |
| Spatial resolution and depths | Inherited from the queried survey geometry and representative component horizons |
| Access | REST/POST SQL query service, SOAP, WFS, WMS, and newer OGC services |
| Authentication | None for current public query service |
| Rate limits | No quota is assumed by OpenSoil; requests are bounded, rate-limited, timed out, retried once, and cached |
| License and citation | Source-data terms remain with USDA; OpenSoil emits a USDA-NRCS SSURGO/SDA citation and leaves unverified license fields null |
| OpenSoil status | supported |
Adapter behavior¶
The adapter calls the official Tabular/post.rest query service with fixed SQL structure. A validated WGS84 point is passed to SDA_Get_Mukey_from_intersection_with_WktWgs84; returned map units are joined to major components and overlapping horizons. Callers cannot submit SQL.
The selected normalized fields are pH (ph1to1h2o_r), organic matter, total sand/silt/clay, one-third-bar bulk density, and electrical conductivity. No unit conversion is applied. The raw route preserves the provider's JSON+COLUMNNAME response.
Known constraints include upstream interruptions, incomplete fields, variable survey coverage, and multiple components for one map unit. A six-hour bounded cache reduces unnecessary upstream load and always reports its timestamp and age.