Vertisols

Vertisols are heavy clay soils with a high proportion of swelling clays with a 2:1 structure. As they dry out (which happens in most years) they form deep wide cracks from the surface downward. Surface soil falls into the cracks, and subsurface soil is pushed upwards, in a kind of pedoturbation called churning, which causes a mixing of the surface and subsurface materials. The following account is taken from FAO (2001).

Connotation. Churning heavy clay soils; from L. vertere, to turn.

Synonyms. Vertisol is a name common to several classifications. More parochial terms are some ‘black cotton soils’ (USA), ‘regur’ (India), ‘vlei soils’ (South Africa), ‘margalites’ (Indonesia), and ‘gilgai’ (Australia).

Definition. FAO (2001) defines Vertisol as soils with

• 1. a vertic horizon within 100 cm from the soil surface, and

• 2. after the upper 20 cm have been mixed, 30 percent or more clay in all horizons to a depth of 100 cm or more, or to a contrasting layer between 50 and 100 cm (e.g., a lithic...