A thick, well-structured, very dark surface horizon with a high base saturation (WRB 2022 3.1.6, pp. 40-41). Every layer of the horizon, from the mineral soil surface down, must have: (1) \>= 50% fine earth and no mulmic material; (2) granular structure, subangular blocky structure of average size \<= 2 cm (very fine, fine or medium), or cloddy / agricultural structure; (3) \>= 1% SOC; (4) moist value \<= 3, dry value \<= 5 and moist chroma \<= 2, or the carbonate-rich (15-40% CaCO3, \>= 1.5% SOC) or the \>= 40% CaCO3 / loamy-sand (value \<= 5, \>= 2.5% SOC) alternatives; (5) \>= 1% more SOC than a parent-material layer of moist value \<= 4, where one is recorded; (6) BS \>= 50%. The layers together must be (7) \>= 30 cm thick. Worm holes belong to the Vermic qualifier, not to this horizon.
Arguments
- pedon
A
PedonRecord.- min_thickness
Minimum thickness in cm (default 30).
Value
A DiagnosticResult recording whether the diagnostic is present, the qualifying layers, and the supporting evidence.