Soil orders

Semiarid Soils [S]

Great soils for rabbits with densities of more than 800 rabbits per square kilometre during plagues.

Semiarid Soils are dry for most of the growing season. Rain is not sufficient to leach through the soil, so lime and salts accumulate in the lower subsoil. Nutrient levels are relatively high, but the soils must be irrigated to produce a crop.

Immature Semiarid soil.
Immature Semiarid soil.
Semiarid soil, Maniototo Basin.
Semiarid soil, Maniototo Basin.

Occurrence

Semiarid Soils occur in the inland basins of Otago and southern Canterbury, where annual precipitation is less than about 500 mm. They cover 1% of New Zealand.

View map View map of Semiarid soils.

Physical properties

Soils have high slaking and dispersion potential, and moderate to high bulk densities. Soil structure is usually weakly developed and the soils are erodible.

Chemical properties

The soils have low organic matter, cation exchange capacity and low iron and aluminium oxide contents. They are weakly buffered. Soluble salts are present in many soils, calcium carbonate is present in most subsoils. Clay minerals are dominated by illite.

Biological properties

Soils have low biological activity because of droughtiness and low organic matter contents.

Soil groups

Soil orders are divided into soil groups based on variation in factors such as drainage status, parent material, chemical and physical properties

[SA] Aged-argillic Semiarid

Reddish coloured clay accumulations

[SZ] Solonetzic Semiarid

Relatively high amount of sodium on clay surfaces

[SJ] Argillic Semiarid

Clay accumulation as thin coatings on peds or in pores

[SI] Immature Semiarid

Features are weakly expressed