14
Recent Soils
Recent Soils are in their prime
the key thing is enough time
with topsoil and a weak B
plants will grow productively
Abstract
Recent Soils cover about 6% of New Zealand and are
developed where material has been deposited, or eroded,
and soil development has recommenced on new parent
materials. Recent Soils occur where repeated deposits are
thin enough, or there has been enough time, for a topsoil
5 cm thick to form. They may also have a weakly
developed B horizon. Many Recent Soils occur on the flat
alluvial flood plains of our major river systems. Such
Fluvial Recent Soils are productive and widely used for
dairy, and other pastoral, farming as well as for cropping
and horticulture. However, many Recent Soils remain at
risk of flooding, and extensive flood protection works
have been installed to safeguard Recent Soils in both
urban and rural areas in many regions. A number of
towns, including Whangarei, Paeroa, Edgecumbe, Whakatane, Gisborne, Wairoa, Palmerston North, Whanganui,
Westport, Hokitika, and Mosgiel, are built, in part, on
Recent Soils, and have been subject to flooding. Recent
Soils also occur on eroded hill and mountain country,
older relatively stable sand dunes, and surfaces mantled
with young tephra deposits. Sandy Recent Soils are
particularly prone to wind erosion, hence maintenance of
vegetation cover to prevent damage is important.
14.1 Important Features of Recent Soils
14.1.1 Concept and Key Features of the Soil
Order
Because of its geologically active plate tectonic setting, and
hence geomorphic instability and generally rapid rates of
natural erosion and deposition, New Zealand has extensive
areas, and a wide variety, of Recent Soils. Recent Soils are
weakly developed, showing limited signs of soil-forming
processes because of youthfulness as a consequence of soil
erosion, or deposition of parent materials, or, occasionally,
because the soil parent material is especially resistant to
weathering. Soil formation is sufficient to develop a distinct
topsoil but a B horizon is either absent or only weakly
expressed as a ‘colour’ B (namely, Bw) horizon. A continuous cover of plants is normally well established. Soil
development in a Recent Soil, albeit limited, is by definition
more advanced than in Raw Soils.
The most economically important and extensive areas of
Recent Soils in New Zealand are on the highly productive
river flood plains where typically thin additions of material
during flooding episodes have allowed the soil to gradually
build up (Fig. 14.1). Such incremental deposition and the
© 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_14
215
Recent Soils
Recent Soils are in their prime
the key thing is enough time
with topsoil and a weak B
plants will grow productively
Abstract
Recent Soils cover about 6% of New Zealand and are
developed where material has been deposited, or eroded,
and soil development has recommenced on new parent
materials. Recent Soils occur where repeated deposits are
thin enough, or there has been enough time, for a topsoil
5 cm thick to form. They may also have a weakly
developed B horizon. Many Recent Soils occur on the flat
alluvial flood plains of our major river systems. Such
Fluvial Recent Soils are productive and widely used for
dairy, and other pastoral, farming as well as for cropping
and horticulture. However, many Recent Soils remain at
risk of flooding, and extensive flood protection works
have been installed to safeguard Recent Soils in both
urban and rural areas in many regions. A number of
towns, including Whangarei, Paeroa, Edgecumbe, Whakatane, Gisborne, Wairoa, Palmerston North, Whanganui,
Westport, Hokitika, and Mosgiel, are built, in part, on
Recent Soils, and have been subject to flooding. Recent
Soils also occur on eroded hill and mountain country,
older relatively stable sand dunes, and surfaces mantled
with young tephra deposits. Sandy Recent Soils are
particularly prone to wind erosion, hence maintenance of
vegetation cover to prevent damage is important.
14.1 Important Features of Recent Soils
14.1.1 Concept and Key Features of the Soil
Order
Because of its geologically active plate tectonic setting, and
hence geomorphic instability and generally rapid rates of
natural erosion and deposition, New Zealand has extensive
areas, and a wide variety, of Recent Soils. Recent Soils are
weakly developed, showing limited signs of soil-forming
processes because of youthfulness as a consequence of soil
erosion, or deposition of parent materials, or, occasionally,
because the soil parent material is especially resistant to
weathering. Soil formation is sufficient to develop a distinct
topsoil but a B horizon is either absent or only weakly
expressed as a ‘colour’ B (namely, Bw) horizon. A continuous cover of plants is normally well established. Soil
development in a Recent Soil, albeit limited, is by definition
more advanced than in Raw Soils.
The most economically important and extensive areas of
Recent Soils in New Zealand are on the highly productive
river flood plains where typically thin additions of material
during flooding episodes have allowed the soil to gradually
build up (Fig. 14.1). Such incremental deposition and the
© 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_14
215