Maps of Fundamental Soil Layers

Soil Moisture Properties

The dominant soil of a land resource inventory area is mapped according to the following key soil physical attributes: profile total available water, profile readily available water, macroporosity 0–0.6 m depth and macroporosity 0.6–0.9 m depth.

Profile Total Available Water

Profile total available water (mm) for the soil profile to a depth of 0.9 m, or to the potential rooting depth (whichever is the lesser). Values are weighted averages over the specified profile section (0–0.9 m) and are expressed in units of mm of water. Profile total available water is important for droughtiness and overall water availability. The classes originate from the work of Gradwell and Birrell (1979), Wilson and Giltrap (1982), and Griffiths (1985), and are described more fully in Webb and Wilson (1995).

Profile Readily Available Water

Profile readily available water for the soil profile to a depth of 0.9 m, or to the potential rooting depth (whichever is the lesser). Values are weighted averages over the specified profile section (0–0.9 m) and are expressed in units of mm of water. Profile total available water is important for droughtiness and plant available water. The classes originate from the work of Gradwell and Birrell (1979), Wilson and Giltrap (1982), and Griffiths (1985), and are described more fully in Webb and Wilson (1995).

Macroporosity (0–0.6 m)

Macroporosity is an expression of the air-filled porosity of the soil at ‘field capacity’. Values are minimum values over the specified profile section (0–0.6 m), and are expressed as a percentage of the soil volume. Macroporosity is important for the characterization of supply of oxygen to plant roots, waterlogging, and ease of drainage. The classes originate from the work of Gradwell (1960) and Gradwell and Birrell (1979), and are described more fully in Webb and Wilson (1995).

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Macroporosity (0.6–0.9 m)

Macroporosity is an expression of the air-filled porosity of the soil at ‘field capacity’. Values are minimum values over the specified profile section (0.6–0.9 m), and are expressed as a percentage of the soil volume. Macroporosity is important for the supply of oxygen to plant roots, waterlogging and ease of drainage at depth in the soil profile. The classes originate from the work of Gradwell (1960) and Gradwell and Birrell (1979), and are described more fully in Webb and Wilson (1995).

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