Brown podzolic

soil Soil, also commonly referred to as earth, is a mixture of organic matter, minerals, gases, water, and organisms that together support the life of plants and soil organisms. Some scientific definitions distinguish dirt from ''soil'' by re ...

s are a subdivision of the Podzolic soils in the British

soil classification Soil classification deals with the systematic categorization of soils based on distinguishing characteristics as well as criteria that dictate choices in use. Overview Soil classification is a dynamic subject, from the structure of the system, ...

. Although classed with podzols because they have an iron-rich, or spodic horizon, they are, in fact intermediate between podzols and

Brown earth Brown earth is a type of soil. Brown earths are mostly located between 35° and 55° north of the Equator. The largest expanses cover western and central Europe, large areas of western and trans-Uralian Russia, the east coast of America and easte ...

s. They are common on hilly land in western Europe, in climates where

precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls from clouds due to gravitational pull. The main forms of precipitation include drizzle, rain, rain and snow mixed ("sleet" in Commonwe ...

of more than about 900mm exceeds

evapotranspiration Evapotranspiration (ET) refers to the combined processes which move water from the Earth's surface (open water and ice surfaces, bare soil and vegetation) into the Atmosphere of Earth, atmosphere. It covers both water evaporation (movement of w ...

for a large part of the year, and summers are relatively cool. The result is that leaching of the soil profile occurs; in which mobile chemicals are washed out of the topsoil, or A horizon, and accumulate lower down, in the B horizon. These soils have large amounts (more than 5%) of organic carbon in the surface horizon, which is therefore dark in colour. In unploughed situations there may be a "mor"

humus In classical soil science, humus is the dark organic matter in soil that is formed by the decomposition of plant and animal matter. It is a kind of soil organic matter. It is rich in nutrients and retains moisture in the soil. Humus is the Lati ...

layer in which the surface organic matter is only weakly mixed with the mineral component. Unlike podzols proper, these soils have no continuous leached E horizon. This is because they are formed on slopes where, over long periods, the topsoil weathered from higher up the slope is continually being carried down the slope by the action of rain, gravity and faunal activity. This means that fresh supplies of iron and aluminium oxides (

sesquioxide A sesquioxide is an oxide of an element (or radical), where the ratio between the number of atoms of that element and the number of atoms of oxygen is 2:3. For example, aluminium oxide and phosphorus(III) oxide are sesquioxides. Many sesquioxid ...

s) are constantly being provided, and leaching ensures a net accumulation of these compounds in the B horizon, giving an orange-brown "rusty" colour which is very distinctive. The aluminum and

ferric In chemistry, iron(III) or ''ferric'' refers to the chemical element, element iron in its +3 oxidation number, oxidation state. ''Ferric chloride'' is an alternative name for iron(III) chloride (). The adjective ''ferrous'' is used instead for i ...

iron compounds in the

subsoil Subsoil is the layer of soil under the topsoil on the surface of the ground. Like topsoil, it is composed of a variable mixture of small particles such as sand, silt and clay, but with a much lower percentage of organic matter and humus. The su ...

also tend to bind the soil particles together, giving a "pellety" fine structure to the soil, and improving permeability, so that despite being in relatively high rainfall areas, the soils do not have the grey colours or mottles of gley soils. In the

World Reference Base for Soil Resources The World Reference Base for Soil Resources (WRB) is an international soil classification system for naming soils and creating legends for soil maps. The currently valid version is the fourth edition 2022. It is edited by a working group of the I ...

, these soils are called Umbrisols, and the Soil Atlas of Europe{{cite book , title = Soil Atlas of Europe , author1=Jones, A. , author2=Montanarella, L. , author3=Jones, R. , publisher = European Soil Bureau Network, European Commission, Soil Atlas of Europe , year = 2005 shows a preponderance of this kind of soil in north-west Spain. There is a tendency for the soils to occur in

ocean The ocean is the body of salt water that covers approximately 70.8% of Earth. The ocean is conventionally divided into large bodies of water, which are also referred to as ''oceans'' (the Pacific, Atlantic, Indian Ocean, Indian, Southern Ocean ...

ic areas, where there is abundant rainfall throughout the year, winters are mild and summers relatively cool. Thus they are common in

Ireland Ireland (, ; ; Ulster Scots dialect, Ulster-Scots: ) is an island in the North Atlantic Ocean, in Northwestern Europe. Geopolitically, the island is divided between the Republic of Ireland (officially Names of the Irish state, named Irelan ...

Scotland Scotland is a Countries of the United Kingdom, country that is part of the United Kingdom. It contains nearly one-third of the United Kingdom's land area, consisting of the northern part of the island of Great Britain and more than 790 adjac ...

Wales Wales ( ) is a Countries of the United Kingdom, country that is part of the United Kingdom. It is bordered by the Irish Sea to the north and west, England to the England–Wales border, east, the Bristol Channel to the south, and the Celtic ...

(where they occupy about 20% of the country) and western England, especially

Devon Devon ( ; historically also known as Devonshire , ) is a ceremonial county in South West England. It is bordered by the Bristol Channel to the north, Somerset and Dorset to the east, the English Channel to the south, and Cornwall to the west ...

Cornwall Cornwall (; or ) is a Ceremonial counties of England, ceremonial county in South West England. It is also one of the Celtic nations and the homeland of the Cornish people. The county is bordered by the Atlantic Ocean to the north and west, ...

and the

Lake District The Lake District, also known as ''the Lakes'' or ''Lakeland'', is a mountainous region and National parks of the United Kingdom, national park in Cumbria, North West England. It is famous for its landscape, including its lakes, coast, and mou ...

. They also occur in the

Appalachian Mountains The Appalachian Mountains, often called the Appalachians, are a mountain range in eastern to northeastern North America. The term "Appalachian" refers to several different regions associated with the mountain range, and its surrounding terrain ...

and on the west coast of

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

References

Pedology Types of soil