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Aquic conditions (USDA Soil Taxonomy, 13th edition)

Source: R/diagnostics-conditions-usda.R
aquic_conditions_usda.Rd

"Soils with aquic conditions are those that currently undergo continuous or periodic saturation and reduction. The presence of these conditions is indicated by redoximorphic features, except in Histosols and Histels." – KST 13ed, Ch 3, p 41.

Usage

aquic_conditions_usda(
  pedon,
  max_top_cm = 100,
  min_redox_pct = 5,
  max_chroma = 2
)

Arguments

pedon

A PedonRecord.

max_top_cm

Maximum depth at which saturation must occur (default 100 – typical for Suborder keys; 200 for some).

min_redox_pct

Threshold for redoximorphic features (default 5 percent).

max_chroma

Maximum chroma indicating reduction (default 2).

Value

A DiagnosticResult with evidence$saturation_type = "endo" / "epi" / NA.

Details

Three types of saturation are defined:

  • Endosaturation: saturated in all layers from the upper boundary of saturation to >=200 cm.

  • Episaturation: saturated in one or more layers within 200 cm with unsaturated layer(s) below.

  • Anthric saturation: cultivated/flood-irrigated.

Implementation (v0.8.x):

  • Saturation is inferred from the presence of redoximorphic features (redoximorphic_features_pct >= 5) and/or a glei horizon (designation containing 'g').

  • Reduction is inferred when chroma <= 2 in the matrix.

  • Artificial drainage is treated as positive aquic when site$artificially_drained == TRUE (deferred – not in current schema).

References

Soil Survey Staff (2022), KST 13ed, Ch. 3, pp 41-44.