5.1.12—Soil texture

Syllabus
First assessment 2026
Objective
5.1.12
Level
HL

Read Soil by Texture

Sand feels gritty, silt smooth or floury, and clay sticky when wet; texture is the relative proportion of these particle sizes.

A settling test estimates proportions by how quickly particles fall. Humus modifies aggregation, water retention and nutrient behaviour but does not change the mineral-size label itself.

A jar with a thick slow-settling layer suggests more clay; gritty feel suggests sand-rich soil.

Colour may reflect humus or iron; texture requires particle feel or measured proportions.

Texture and structure are different: particle proportions do not fully describe aggregates and pore spaces.