and Entisols soil orders, see Chap. 5 for more details) are extracted from the latest Keys to Soil Taxonomy (Soil Survey Staff 2014) with slight changes to fit soil classification of Kuwait. An official permission has been granted by the USDA management to extract information relevant to the soils of Kuwait.

3.2Basic System of Horizon and Layer Designations

While describing the morphological features of the soil profiles and/or auger holes to classify a soil, four kinds of symbols are used in various combinations to designate properties of horizons and layers:

•Capital letters (A, E, B, C, R etc.) are allocated to the master horizons and layers.

•Lowercase letters (small letters) are used as suffixes (e.g., Ak) to describe specific characteristics of master horizons and layers.

•Numbers are used both as suffixes to indicate vertical subdivisions (e.g., Ak1, Ak2, Ak3 etc.) within a horizon or layer and as prefixes to indicate discontinuities.

•Special symbols are used to indicate layers formed in human-transported material or sequences of horizons having otherwise identical designations.

3.2.1 Master Horizons and Layers

In the USDA-NRCS (Soil Survey Staff 2014; Soil Science Division Staff 2017) system of soil classification, the capital letters A, B, C, R represent the master horizons and layers of soils identified in Kuwait. Each horizon-layer has specific definition. These letters are the base symbols to which other characters are added to complete the designations. Most horizons and layers are given a single capital-letter symbol; some require two. In this section, preference is given to the horizons and layers identified in Kuwait, these are: A, B, C and R. The definitions are restricted to the features observed in Kuwait, rather than giving detailed explanation to represent properties in other soils not related to Kuwait.

A Horizons

A horizons are mineral horizons that formed at the soil surface or below an O (organic) horizon. It may contain humified organic matter mixed with mineral matter and show signs of cultivation.

B horizons

Mineral horizons formed below an A, or E, it shows signs of illuvial accumulation of clay, carbonates, gypsum etc.) demonstrating the operation of soil genesis (pedogenesis) process and have structure other than rock structure.

C horizon

C horizons or layers lack the properties of O, A, E and B horizons and are little affected by pedogenesis.

R Layers

R layers consist of strongly cemented to indurated bedrock. Limestone and sandstone are examples of bedrock designated by the letter R.

In the south of Kuwait deep sandy soils are identified. These soils do not show evidence of pedogenesis, such as accumulation of clay, carbonates and gypsum. However, in the north of Kuwait the pedogenesis has been observed in the form of distinct accumulation of secondary carbonates and gypsum. In the west of Kuwait gypsic hardpan soils have been mapped. The lithified layers (sandstone) are designated as R.

3.2.2 Suffix Symbols

The master horizons and layers (A, B, C, R) also show lowercase letters (such as Ak, By) called suffix symbols. These symbols are used to designate specific subordinate distinctions within master horizons and layers. In Kuwait, b, k, m, t, y and z are used. Other suffix symbols (kk, n, p, w, and yy) were not recorded, but are likely to occur in Kuwait and may be useful to record for future work. These are described below:

b Buried genetic horizon

This symbol indicates identifiable buried horizons with major genetic features that were developed before burial. Genetic horizons may or may not have formed in the overlying material, which may be either like or unlike the assumed parent material of the buried horizon.

In Kuwait mobile sand in the desert, in some places has buried the genetic horizon, such a feature was observed in the Wafra area, where calcic genetic horizon was buried by a thick layer of sandy surface mantle.

k Accumulation of secondary carbonates

This symbol indicates an accumulation of visible pedogenic calcium carbonate (less than 50 percent, by volume). Carbonate accumulations in the soils of Kuwait were found in the form of disseminated carbonates and secondary calcium carbonates accumulations. The symbol k can be used with horizons showing very slightly to strong effervescence with dilute hydrochloric acid.

kk Engulfment of horizon by secondary carbonates

This symbol indicates major accumulations of pedogenic calcium carbonate. The suffix kk is used when the soil fabric is plugged with fine grained pedogenic carbonate (50 percent or more, by volume) that occurs as an essentially continuous medium. The suffix corresponds to stage III of the carbonate morphogenetic stages (Gile et al. 1966) or a higher stage.

m Pedogenic cementation

This symbol indicates continuous or nearly continuous pedogenic cementation. It is used only for horizons that are more than 90 percent cemented but may be fractured. The cemented layer is physically root-restrictive. The predominant cementing agent (or the two dominant ones) can be indicated by letter suffixes, singly or in pairs. The horizon suffix km indicates cementation by carbonates and ym indicates cementation by gypsum.

n Accumulation of sodium

This symbol indicates an accumulation of exchangeable sodium.

p Tillage or other disturbance

This symbol indicates a disturbance of a horizon by mechanical means, ploughing, or similar uses. A disturbed mineral horizon is designated Ap even though it is clearly a former B or C horizon.

r Weathered or soft bedrock.

This symbol is used with C horizons to indicate layers of bedrock that are moderately cemented or less cemented. Examples are weathered igneous rock and partly consolidated sandstone, siltstone, or shale. The excavation difficulty is low to high.

t Accumulation of silicate clay

This symbol indicates an accumulation of silicate clay that either has formed within a horizon and subsequently has been translocated within the horizon or that has