Cohesic horizon (WRB 2022, Chapter 3.1.7)

A subsurface horizon with a massive or weak subangular blocky structure, poor in organic matter and iron oxides, with a kaolinite-dominated, low-activity clay fraction, and hard when dry. It is the diagnostic basis of the Cohesic qualifier and corresponds to the caracter coeso of the Brazilian SiBCS (typical of the coastal "Tabuleiros" Latossolos and Argissolos).

Usage

cohesic(
  pedon,
  max_oc = 0.5,
  min_clay = 15,
  max_cec_per_clay = 24,
  min_thickness = 10
)

Arguments

pedon

A PedonRecord.

max_oc

Maximum soil organic carbon (%), default 0.5.

min_clay

Minimum clay (%), default 15.

max_cec_per_clay

Maximum CEC in cmol_c per kg clay, default 24.

min_thickness

Minimum thickness in cm, default 10.

Value

A DiagnosticResult.

Details

Diagnostic criteria (all required): mineral material with (1) < 0.5% soil organic carbon; (2) >= 15% clay; (3) a CEC (by 1 M NH4OAc, pH 7) of < 24 cmol_c per kg clay; (4) a massive or weak subangular blocky structure; (5) not cemented; (6) a rupture-resistance class, when dry, of at least hard; and (7) a thickness of >= 10 cm.

References

IUSS Working Group WRB (2022), Chapter 3.1.7, Cohesic horizon.