Add a property

Before adding a canonical property, define what the concept includes and excludes. “Available phosphorus,” “cation exchange capacity,” and “pH” are method-dependent families, not context-free numbers.

Required changes

1. Add ID, display name, description, standard unit, aliases, conversion notes, method warning, and status to the property registry.
2. Document method distinctions and approved units.
3. Map provider columns only when they represent the same canonical concept.
4. Preserve original field, value, unit, depth, and method in each observation.
5. Add success, null, alias, unsupported-provider, and schema tests.
6. Add a decision record for any conversion or potentially ambiguous mapping.

Conversion review

A conversion must state input/output units, formula, precision behavior, domain limits, and source. The response must append a transformation. Derived relationships—such as organic matter to organic carbon—are not unit conversions and require a method/model with their own uncertainty and warnings.