To help users become acquainted with the attributes needed, and related codes, the following glossary is provided.
Soil Texture A measure of the behaviour of a handful of soil when moistened and kneaded into a bolus and then pressed out between thumb and forefinger. Nineteen grades of texture, such as sand, loamy sand and silt loam, are commonly recognised (See table below).
Texture Groups The nineteen texture grades are arranged in six groups as shown below.
Subsoil The underlying layer which is immediately beneath any A horizon. It is the main B horizon (usually the B2) and is often encountered between 30-60 cm.
Solum The upper and most weathered part of the soil profile: the A and B horizons (SSSA, 1978).
Texture Profile Change of texture with depth of soil. In ASIS the texture profile is automatically calculated from the texture entry of the topsoil, subsoil and a point between if a B1 or an A2 (E) horizon that increases in clay from the A1 is present. Four texture profiles have been recognised as follows (Northcote, 1984).
0. Organic-soil profile dominated by organic matter. Soil which has 20 % or more organic matter and less than 15 % clay or 30 % or more organic matter and more than 15 % clay in the surface 30 cm has an organic texture profile, e.g. Acid Peat and Neutral-Alkaline Peat.
1. Uniform-soil with no clearly defined texture boundary and the equivalent of one texture group, e.g. Black Earth and Chernozem.
2. Gradational-soil showing increasingly finer texture grades on passing down the profile e.g. Krasnozem and Red Earth.
3. Duplex-soil profile with a texture contrast of the equivalent of 1.5 texture groups or greater between the A and B horizons, e.g. Red-Brown Earth and Yellow Podzolic Soil.
Topsoil Salinity (1:5 water) Electrical conductivity (EC) in the surface 10 cm of soil profile (topsoil) in dS m–1. Four salinity classes have been designated as follows:
0. soil with EC<0.63 dS m–1 , e.g. Podzol and Chocolate Soil.
1. soil having EC 0.63–1.25 dS m–1 , e.g. Wiesenboden.
2. soil having EC 1.25–2.5 dS m–1 , e.g. Desert Loam.
3. soil with EC>2.50 dS m–1 , e.g. Solonchak.
Subsoil Salinity (1:5 water) Electrical conductivity of the subsoil in
dS m–1 . Four salinity classes have been defined as follows:
0. soil with EC<0.63 dS m–1 in, e.g. Red and Yellow Podzolic Soil.
1. soil having EC 0.63–1.25 dS m–1, e.g. Solonized Brown Soil and Black Earth.
2. soil having EC 1.25–2.5 dS m–1 , e.g. Solonetz and Humic Gley.
3. soil with EC>2.50 dS m–1 , e.g. Solonchak and Desert Loam.
Topsoil Organic Matter % Percentage of organic matter in topsoil. Four levels of organic matter are given.
0. soil with O.M.<2.5 %, e.g. Yellow Earth and Earthy Sand.
1. soil with O.M. 2.5–10 %, e.g. Euchrozem and Prairie Soil.
2. soil with O.M.10–20 %, e.g. Humus Podzol and Alpine Humus Soil.
3. soil with O.M.>20 %, e.g. Peaty Podzol and Acid Peat.
Subsoil Acidity (pH) 1:5 water pH value of the subsoil. It is usually within the range of 3–11.
Subsoil Structure A classification on the basis of the degree of structure development. Four grades of structure recognised as follows:
0. Massive–soil without observable aggregation, e.g. Siliceous Sand and Red Earth.
1. Weak–soil with <1/3 pedality and poor and barely observable aggregation, e.g. Earthy Sand.
2. Moderate–soil with 1/3-2/3 pedality and moderately aggregation, e.g. Yellow Podzolic Soil.
3. Strong–soil with >2/3 pedality and quite aggregation, e.g. Krasnozem.
Solum Mottling Areas of different colour or shades of colour interspersed with the dominant colour. Three options have been recognised:
0. soil without mottling in profile, e.g. Calcareous Sand and Desert Loam.
1. soil with some mottling in profile, e.g. Grey-Brown Podzolic and Red-Brown Earth .
2. soil with much mottling in profile, e.g. Yellow Podzolic Soil and Humic Gley.
Subsoil Clay % Percentage of clay in subsoil. This may be estimated from the field texture (Table 5.3) or a particle size analysis (PSA).
A2 (E) Horizon A pale horizon in which the main features are loss of clay, iron or aluminium, with the resultant concentration of quartz and silt sizes particles. Four options have been given:
0. soil without A2 (E) horizon, e.g. Solonchak and Earthy Sand.
1. soil with an unbleached A2 (E) horizon e.g. some Red Podzolic Soil.
2. Sporadic bleach A2 (E) horizon–soil with irregular bleached portions, e.g. Desert Loam.
3. Conspicuous bleached A2 (E) horizon–soil in which 80 % or more of the A2 (E) is bleached, e.g. Podzol and Soloth.
Concretions Local concentrations of chemical compounds such as calcium carbonate or iron oxide in the form of nodules. Three options have been given:
0. soil without concretions in the profile, e.g. Podzol and Non-Calcic Brown Soil.
1. soil with some concretions in the profile, e.g. Prairie Soil and Red Podzolic Soil.
2. soil with many concretions in the profile, e.g. Lateritic Podzolic Soil.
Crust A surface layer, ranging in thickness from a few millimetres to a few centimetres, that is usually compact, hard and brittle when dry. There are two options for this attribute:
0. soil without a crust, e.g. Chernozem and Krasnozem.
1. soil with a crust, e.g. Desert Loam and Solonchak.
Hardpan A silica cemented red or brown soil layer in the lower A or B horizon. There are two options for this attribute:
0. soil without a hardpan, e.g. Red Podzolic Soil and Red-Brown Earth.
1. soil with a hardpan, e.g. Red and Brown Hardpan Soil.
Topsoil CaCO3 % Percentage of calcium carbonate in the topsoil. Four classes of calcium carbonate have been recognised:
0. soil without calcium carbonate, e.g. Solonetz and Krasnozem.
1. soil with CaCO3 =1–10 %, e.g. Red Calcareous Soil and Rendzina.
2. soil with CaCO3 =10–30 %, e.g. Grey-Brown Calcareous Soil.
3. soil with CaCO3>30 %, e.g. Calcareous Sand.
Subsoil CaCO3 % Percentage of calcium carbonate in the subsoil. Four classes of calcium carbonate have been recognised:
0. soil without calcium carbonate, e.g. Podzol and Krasnozem.
1. soil with CaCO3 =1-10 %, e.g. Red-Brown Earth and Desert Loam.
2. soil with CaCO3=10-30 %, e.g. Calcareous Red Earth and Solonchak.
3. soil with CaCO3>30 %, e.g. Calcareous Sand.
Gypsum Two options have been given for gypsum in the solum:
0. soil without gypsum, e.g. Black Earth and Chernozem.
1. soil with gypsum, e.g. Desert Loam and Solonchak.
Pedological Subsoil A subsoil showing pedological development expressed as some combination of colour, texture or structure contrast with other layers. Two options have been recognised:
0. soil without a pedological subsoil, e.g. Alluvial Soil and Lithosol.
1. soil with a pedological subsoil, e.g. Red and Yellow Podzolic Soil.
Alluvial Layer A recently deposited alluvium exhibiting essentially no horizon development. Two options have been given:
0. soil without an alluvial layer, all soil groups but Alluvial Soil.
1. soil with an alluvial layer, Alluvial Soil.
Parent Material The unconsolidated and more or less weathered material from which soil horizons are developed by pedogenic processes. Three kinds of parent material have been recognised:
0. basic material such as basalt.
1. limestone and other calcareous material.
2. others containing appreciable quartz, e.g. granite.
Subsoil Colour An attribute which is defined in terms of hue, value and chroma using the Munsell soil colour charts (1954).
Hue–Caused by light of certain wavelengths and changes with wavelength. The hue of a colour indicates its relation to Red, Yellow, Green, Blue and Purple.
Value–The relative lightness of colour and is approximately a function of the square root of the total amount of light.
Chroma–The relative purity, strength, or saturation of a colour.
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