Irragric horizon (WRB 2022): topsoil thickened by irrigation deposits.

v0.9.317: the criteria of WRB 2022 Ch 3.1.18 (p. 50-51), tested on every stack of contiguous layers from the mineral soil surface (a surface horizon of mineral material), each against the layer directly below it:

1. soil aggregate structure or cloddy structure in \(\ge\) 90% by volume;

2. a clay content \(\ge\) 10% (relative) and \(\ge\) 3% (absolute) higher than that of the layer directly buried; the fine clay alternative is not recorded, so a smaller increase leaves it undecided;

3. differences between subhorizons of < 20% (relative) or < 4% (absolute) in silt, clay and carbonates (also in the medium, fine and very fine sand, which soilKey does not record: undecided for more than one layer unless a recorded difference fails);

4. \(\ge\) 0.3% SOC in each layer and \(\ge\) 0.5% on a weighted average;

5. \(\ge\) 25% traces of soil animal activity (worm_holes_pct, weighted);

6. evidence that the land surface has been raised: soilKey records no such evidence, so this criterion is undecided;

7. \(\ge\) 20 cm thick (min_thickness).

The horizon is therefore never established from the data: FALSE when every stack fails a criterion, NA otherwise. Until v0.9.316 any Ap or Au of 20 cm passed.

Usage

irragric(pedon, min_thickness = 20)

Arguments

pedon

A PedonRecord.

min_thickness

Numeric threshold or option (see Details).

Value

A DiagnosticResult recording whether the diagnostic is present, the qualifying layers, and the supporting evidence.