Fig. 3.4 A salic diagnostic horizon in a Typic Aquisalids profile in the coastal area

3.4Diagnostic Soil Characteristics

Diagnostic soil characteristics are features of the soil that are used in various places in the keys or in the definitions of diagnostic horizons. In the soils of Kuwait, following are the diagnostic soil characteristics.

3.4.1 Free Carbonates

The term “free carbonates” is used as a criterion for the isotic mineralogy (no free carbonates) class. It refers to soil carbonates that are uncoated or unbound and that effervesce visibly or audibly when treated with cold, dilute HCl. The term “free carbonates” is nearly synonymous with the term “calcareous.” Soils that have free carbonates generally have calcium carbonate as a common mineral, although sodium and magnesium carbonates are also included in this concept. Soils or horizons with free carbonates may have inherited the carbonate compounds from parent materials without any translocation or transformation processes acting on them. There is no implication of pedogenesis in the concept of free carbonates, as

there is in identifiable secondary carbonates (defined below), although most forms of secondary carbonates are freely effervescent.

3.4.2 Identifiable Secondary Carbonates

The term “identifiable secondary carbonates” is used in the definitions of a number of taxa. It refers to translocated authigenic calcium carbonate that has been precipitated in place from the soil solution rather than inherited from a soil parent material, such as calcareous loess or limestone residuum.

Identifiable secondary carbonates either may disrupt the soil structure or fabric, forming masses, nodules, concretions, or spheroidal aggregates (white eyes) that are soft and powdery when dry, or may be present as coatings in pores, on structural faces, or on the undersides of rock or pararock fragments. If present as coatings, the secondary carbonates cover a significant part of the surfaces. Commonly, they coat all of the surfaces to a thickness of 1 mm or more. If little calcium carbonate is present in the soil, however, the surfaces may be only partially coated. The coatings must be thick enough to be visible when moist. Some horizons are entirely engulfed by carbonates. The color of these horizons is largely determined by the carbonates. The carbonates in these horizons are within the concept of identifiable secondary carbonates.

The filaments commonly seen in a dry calcareous horizon are within the meaning of identifiable secondary carbonates if the filaments are thick enough to be visible when the soil is moist. Filaments commonly branch on structural faces.

3.4.3 Aquic Conditions

Soils with aquic (L. aqua, water) conditions are those that currently undergo continuous or periodic saturation and reduction. The presence of these conditions is indicated by redoximorphic features, except in artificially drained soils. Artificial drainage is defined here as the removal of free water from soils having aquic conditions by surface mounding, ditches, or subsurface tiles or the prevention of surface or ground water from reaching the soils by dams, levees, surface pumps, or other means. In these soils water table levels and/or their duration are changed