Geoscience Reference
In-Depth Information
vertic
expanding clay with signs of swelling, shrinking,
cracking, and hummocks
England and Wales
Major group
Prominent characteristics
Classification system of the Soil Survey
of England and Wales
1
Terrestrial
Recent parent materials with little
raw soils
alteration and no pedogenic horizons,
e.g. scree, boulder fields
The mapping of the soils of Great Britain grew out of the
need to maximize agricultural production from the land
during and immediately after the Second World War. For
many years the Soil Survey of England and Wales was
based at Rothamsted Experimental Station, but is now at
Cranfield University, Silsoe, Bedfordshire, under the aegis
of the National Soil Resources Institute (NSRI). The Soil
Survey of Scotland has always been based at the Macaulay
Institute for Soil Research (MISR), Aberdeen. The systems
of soil classification used by the two organizations are not
identical, but the situation is not as confusing as might
appear at first sight, because names and, more important,
the underlying concepts have much in common. Both
systems use the
soil series
as the local-scale mapping unit.
A soil series contains soils with a similar sequence of soil
horizons and a similar degree of soil development, which
occur on the same parent material, either rock or
superficial deposit. The Soil Survey of England and Wales
is a hierarchical system with ten major groups, forty-
three groups, eighty-three subgroups and about 700
soil series (Avery 1980).
Table 18.5
gives the names and
dominant features of the major groups.
Figure 18.16
s
hows the distribution of soilscapes in
England and Wales. This map, produced in 2004, reminds
us that soils do not occur in the landscape of any place on
Earth as independent natural bodies. They occur in
landscapes consisting of parent materials, regional
climates, vegetation and land use, relief and topography
and physiographic evolution. In this sense this map is an
important contribution to understanding soils as
integrated and multifunctional parts of our natural
regions, even though those regions have always been
modified by human activities. In this sense this important
map revisits the underlying concepts of soil science
propounded by Dokuchaiev a century ago.
2
Raw gley soils Mineral soils permanently waterlogged,
e.g. intertidal flats, salt marshes
3
Lithomorphic
Shallow, rock-dominated, with only a
soils
surface organic horizon, and rock or
unconsolidated material within 30 cm
4
Pelosols
Slowly permeable, clayey soils,
prominent cracks on drying
5
Brown soils
Brown colour, widespread below 300 m,
leaching of ions and/or clay
6
Podzolic soils
Acid weathering produces acid organic
matter and accumulations of iron,
aluminium and/or organic matter in the B
horizon
7
Surface-water
Mottling within the top 40 cm, slowly
gleys
permeable
8
Groundwater
Waterlogging produced by fluctuating
gleys
groundwater table, often on permeable
parent materials
9
Man-made
Formed on materials produced by human
soils
activities, manures, refuse, quarrying,
mining
10 Peat soils
Organic soils of undecomposed or
partially decomposed plant remains
under waterlogged conditions
realized, however, that some soils are formed in several
zones (e.g. gleys, alkali soils, limestone soils); these he
called
transitional soils
. There are also soils which are not
controlled by zonal effects, which he termed
abnormal
soils
(e.g. alluvium, aeolian deposits). Sibirtsev, a follower
of Dokuchaiev, called the three types of soils
zonal
,
intrazona
l and
azonal
soils respectively. This concept of
soil zonality classifies soils which primarily reflect climate
and vegetation as normal or zonal. Those soils which
reflect some local factor such as excess water or carbon-
ates, usually related to relief and parent material, are
intrazonal and may occur in several geographic zones.
Similarly, azonal soils cross zonal boundaries and are
essentially young soils on raw deposits.
During the twentieth century one of the major
additions to the concepts of soil science was the innovative
concept of the
catena
, introduced by Milne in the 1930s
whilst studying the regular repetition of soils in East
Africa. The term (Latin
catena
, 'chain') was originally
used to designate a complex mapping unit, but later soil
scientists came to recognize it as a fundamental unit in
the landscape, reflecting how soils are influenced by slope,
We have seen that the Russian soil scientist Dokuchaiev
in the late nineteenth century was the first to recognize
that soils are independent natural bodies reflecting the
effects of both zonal and local soil-forming agents. He