Introduction - Soil Geography of the USA: A Diagnostic-Horizon Approach - page 8

Table 1.6 Role of soil-forming factors in diagnostic horizons a
Horizon Climate Organisms Relief Parent material Time Humans

Epipedons
Anthropic

X

Folistic x X

Histic x X

Melanic X

Mollic x X

Ochric x X

Plaggen X

Umbric x X

Subsurface
Agric X

Albic x x x

Argillic x x x

Calcic x x x

Cambic X

Duripan X x

Fragipan X

Glossic x x x

Gypsic X x

Kandic x x x

Natric x x x

Ortstein x x x

Oxic X x

Petrocalcic x x x

Petrogypsic x x x

Placic x x X

Salic X x

Sombric X x

Spodic x x x

a Large-case X

most important; small-case x less important

¼ ¼

1.2 Diagnostic Horizons and the Soil-Forming Processes

Bockheim and Gennadiyev ( 2000 ) related key soil-forming processes to the soil
orders and the key diagnostic horizons defining these orders (Table 1.7 ). Seventeen
generalized soil-forming processes were identified, briefly discussed, and linked to
soil taxa and diagnostic horizons, properties, and materials in ST and the WRB. The
processes were illustrated in simple diagrams that included (1) argilluviation,
(2) biological enrichment of base cations, (3) andisolization, (4) paludization,
(5) gleization, (6) melanization, (7) ferrallitization, (8) podzolization, (9) base
cation leaching, (10) vertization, (11) cryoturbation, (12) salinization, (13) calcifi-
cation, (14) solonization, (15) solodization, (16) silicification, and (17) anthroso-
lization. Personal comments to the authors suggested that “cambisolization” be
added as an 18th process and that the calcification process should differentiate