Soil structure: Soil structure describes the arrangement of the solid particles of the soil and of the pore space located between them.

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When a soil (in the profile pit) does not show rock structure, we say there is soil structure (see Figure 6.1, 6.2 and 6.3).

Figure 6.1: Soil Structure and Rock Structure (Example 1; the banded gneiss is clearly visible in the saprolite)

Figure 6.2: Soil Structure (Example 2; structural elements are clearly separated by clearly visible openings)

A remark: One of the requirements of the Cambic horizon (a diagnostic horizon defined in soil classification systems, USDA , FAO, or WRB) is to show more than 50% of soil structure.

A very weathered gneiss (saprolite) will still show bands of the weathered felsic and mafic minerals, in which case decision should be taken whether rock structure is more or less than 50% (see Figure 6.3).

Figure 6.3: Soil Structure and Rock Structure (Example 3)