4
Brown Soils
From the Wairarapa hills to the Southland plains
Brown Soils occur in places with good rains
The hard-working Brown Soils support our pastoral farms,
polyhedral structures are just one of their charms.
Abstract
Brown Soils are New Zealand’s most extensive soil order
covering about 43% of the country. Brown Soils occur on
the moister hill and mountain lands throughout New
Zealand except where tephra deposits predominate.
Brown Soils also occur on flat to rolling lands in wetter
regions such as the Southland lowlands. Most Brown
Soils occur in areas with mean annual rainfall greater than
about 800 mm in the South Island, and 1000 mm in the
North Island. Sandy Brown Soils and stony Brown Soils
may form in areas with lower rainfalls in materials with
low (<75 mm) water holding capacity. Brown Soils have
grey-brown topsoils, brown to yellowish brown subsoils,
and profiles with A–B–C horizonation. They form from a
wide range of parent materials, predominantly siliceous
quartzo-feldspathic rocks (e.g. greywacke, mudstone,
schist, rhyolite) and their derivatives (e.g. sand dunes,
colluvium, alluvium, and loess). Brown Soils are moderately weathered with moderate to strong leaching. The
distinctive brown colours are due to thin coatings of iron
and aluminium hydrous oxides, or aluminosilicates,
potentially including allophane and ferrihydrite, on particle surfaces. The Brown Soils underlie much of New
Zealand’s sheep and beef production along with dairying,
cropping, plantation forestry, and extensive areas of
public conservation land.
4.1 Important Features of Brown Soils
4.1.1 Concept and Key Features of the Soil
Order
Brown Soils are the work horse of New Zealand’s hill country
and the Southland plains (Fig. 4.1). Brown Soils have a brown
or yellow-brown subsoil below a dark grey-brown topsoil. The
Brown Soils are part of the zonal sequence of soils that
reflect increasing rainfall from Semiarid Soils (dry spring to
autumn), through Pallic Soils (dry summer), to Brown Soils
(usually moist), Ultic Soils (moist and warmer), and Podzol
Soils (highly leached and rarely dry). Because Brown Soils are
our predominant soil, they tend to exemplify some of New
Zealand’s common national soil characteristics, namely, moist
cool temperate climate, generally moderate weathering,
acidity, and well-stocked soil organic matter.
The characteristic brown colouring of Brown Soils is
attributable to iron and aluminium oxides dispersed
throughout the soil mass. Some Allophanic Brown Soils
occur in areas with limited tephra inputs that intergrade
towards the Allophanic Soils of the central and western North
Island. However, Allophanic Brown Soils also occur in the
absence of tephra in the South Island high country as a result
of strong leaching (especially desilication) that enables small
to moderate amounts of allophane and ferrihydrite to form.
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021
A. E. Hewitt et al., The Soils of Aotearoa New Zealand, World Soils Book Series,
https://doi.org/10.1007/978-3-030-64763-6_4
57
Brown Soils
From the Wairarapa hills to the Southland plains
Brown Soils occur in places with good rains
The hard-working Brown Soils support our pastoral farms,
polyhedral structures are just one of their charms.
Abstract
Brown Soils are New Zealand’s most extensive soil order
covering about 43% of the country. Brown Soils occur on
the moister hill and mountain lands throughout New
Zealand except where tephra deposits predominate.
Brown Soils also occur on flat to rolling lands in wetter
regions such as the Southland lowlands. Most Brown
Soils occur in areas with mean annual rainfall greater than
about 800 mm in the South Island, and 1000 mm in the
North Island. Sandy Brown Soils and stony Brown Soils
may form in areas with lower rainfalls in materials with
low (<75 mm) water holding capacity. Brown Soils have
grey-brown topsoils, brown to yellowish brown subsoils,
and profiles with A–B–C horizonation. They form from a
wide range of parent materials, predominantly siliceous
quartzo-feldspathic rocks (e.g. greywacke, mudstone,
schist, rhyolite) and their derivatives (e.g. sand dunes,
colluvium, alluvium, and loess). Brown Soils are moderately weathered with moderate to strong leaching. The
distinctive brown colours are due to thin coatings of iron
and aluminium hydrous oxides, or aluminosilicates,
potentially including allophane and ferrihydrite, on particle surfaces. The Brown Soils underlie much of New
Zealand’s sheep and beef production along with dairying,
cropping, plantation forestry, and extensive areas of
public conservation land.
4.1 Important Features of Brown Soils
4.1.1 Concept and Key Features of the Soil
Order
Brown Soils are the work horse of New Zealand’s hill country
and the Southland plains (Fig. 4.1). Brown Soils have a brown
or yellow-brown subsoil below a dark grey-brown topsoil. The
Brown Soils are part of the zonal sequence of soils that
reflect increasing rainfall from Semiarid Soils (dry spring to
autumn), through Pallic Soils (dry summer), to Brown Soils
(usually moist), Ultic Soils (moist and warmer), and Podzol
Soils (highly leached and rarely dry). Because Brown Soils are
our predominant soil, they tend to exemplify some of New
Zealand’s common national soil characteristics, namely, moist
cool temperate climate, generally moderate weathering,
acidity, and well-stocked soil organic matter.
The characteristic brown colouring of Brown Soils is
attributable to iron and aluminium oxides dispersed
throughout the soil mass. Some Allophanic Brown Soils
occur in areas with limited tephra inputs that intergrade
towards the Allophanic Soils of the central and western North
Island. However, Allophanic Brown Soils also occur in the
absence of tephra in the South Island high country as a result
of strong leaching (especially desilication) that enables small
to moderate amounts of allophane and ferrihydrite to form.
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021
A. E. Hewitt et al., The Soils of Aotearoa New Zealand, World Soils Book Series,
https://doi.org/10.1007/978-3-030-64763-6_4
57