Major Soil Types of the Other Continents

25 min

Let's begin

The rules you have learned for Africa work everywhere. Where it is wet, water washes the soil down; where it is dry, water is drawn up; and the vegetation decides how much humus is added. The other continents add two climates Africa lacks, the long cold winters of the far north and the cool, moist forests of the middle latitudes, and with them two famous soils: the grey, leached podzol and the black, fertile chernozem.

Figure 6. Soil belts from the Arctic to the deserts of Central Asia. Drawn by Ganzaa.

The main soils of the other continents

Soil	Climate and vegetation	Where	Characteristics and use
Tundra soils	Very cold; mosses and lichens	Northern Canada, Alaska, northern Russia	Thin, waterlogged (gleyed) over permanently frozen ground (permafrost); almost no farming
Podzols	Cold winters, wet; coniferous forest (taiga)	Canada, Scandinavia, Russia and Siberia	Acid, strongly leached, ash-grey upper horizon; poor for crops; used for forestry
Brown earths (brown forest soils)	Mild and wet; deciduous forest	Western and central Europe, eastern USA, north-eastern China	Moderately leached, well mixed by earthworms; fertile once cleared; mixed farming
Chernozems and chestnut soils	Warm summers, cold winters, fairly dry; grassland (steppe, prairie, pampas)	Ukraine and southern Russia, the North American prairies, the Pampas of Argentina	Thick black humus over a calcium-rich layer; among the most fertile soils on Earth; wheat and maize
Desert soils	Very dry	South-western USA, Atacama, Arabia, Central Asia, interior Australia	Thin, little humus, often salty; grazing, or crops with irrigation
Latosols	Hot and wet; rainforest	Amazon Basin, South-East Asia	As in the Congo Basin: deep, red, leached, poor once cleared
Alluvial and loess soils	Any climate; along great rivers, or where wind has laid down fine dust (loess)	Ganges–Brahmaputra plains, the Mississippi valley, northern China's Loess Plateau	Deep, fertile, easy to work; support very dense farming populations, but loess erodes easily

Definition

Permafrost: ground that stays frozen all year round for at least two years in a row.

Loess: fine, yellowish dust carried and dropped by the wind, which forms deep, fertile but easily eroded soils.

Worked example

Worked example 1: podzol and chernozem compared. Explain why a chernozem is far more fertile than a podzol.

	Podzol (taiga)	Chernozem (steppe)
Water movement	Rain greater than evaporation: strong leaching washes nutrients down	Evaporation about equal to or greater than rain: weak leaching, calcium stays
Organic matter	Needle litter is acid and rots slowly: thin, acid humus	Grass roots die each year deep in the soil: thick, rich humus
Soil life	Few earthworms in the acid, cold soil	Many burrowing animals mix the humus downwards
Result	Acid, pale, infertile	Black, crumbly, very fertile

Worked example

Worked example 2: soils and Africa compared. Which soils of the other continents have African equivalents, and which do not?

Equivalents: latosols (Amazon and Congo), desert soils (Atacama and Sahara), alluvial soils (Ganges and Nile), Mediterranean soils (southern Europe and the Maghreb), black clay soils (the Deccan of India and the Gezira).
No African equivalent: tundra soils and podzols, because Africa has no polar or cold, wet coniferous forest climate; true chernozems are also absent, because Africa has no cold-winter grasslands.

Soils under pressure

Soil forms over hundreds or thousands of years but can be lost in a few seasons. A world assessment by the Food and Agriculture Organization (FAO) in 2015 found that 33% of the world's land is moderately to highly degraded, through erosion, salinization, compaction, acidification and chemical pollution. The causes are the processes you have studied, speeded up by people: cleared slopes erode, badly drained irrigation salts the soil, and heavy machines compact it. In S2 you studied how Rwanda fights soil erosion with terraces, trees and grass strips; the same methods are used across the world.

Food and Agriculture Organization of the United Nations (FAO): The Status of the World's Soil Resources. Listen for the main threats to soils, and compare them with the processes in lesson 2.

Warning

Names differ between systems. Textbooks use older names (podzol, chernozem, latosol); the international system (WRB) and the US system use others (latosols are ferralsols in WRB and oxisols in the US system; chernozems are part of the US mollisols). In the exam, use the names your teacher and textbook use, and say which system you mean if you use another.

Tip

Read soil from the climate. Faced with an unfamiliar place, ask three questions: Is it hot or cold? Is rain greater or less than evaporation? Forest or grass? Cold and wet with conifers gives podzol; dry grassland gives chernozem; hot and wet forest gives latosol; very dry gives desert soil.

Practice

Name the soil found under the taiga and give two of its characteristics.
Name three regions of the world where chernozems are found.
What is permafrost, and how does it affect tundra soils?
Why are there no podzols in Africa?
Explain why the Ukrainian steppe is one of the world's great wheat-growing regions.
Name two soils of other continents that are similar to soils in Africa, and say where each is found.
According to the FAO's 2015 assessment, what share of the world's land is moderately to highly degraded? Name three causes.
"Soil is a non-renewable resource." Explain what this means and suggest two ways farmers can protect soil.

Show answersHide answers

Podzol: acid; strongly leached; ash-grey upper (E) horizon; iron pan in the B horizon; poor for crops (any two).
Any three: Ukraine and southern Russia; the North American prairies; the Pampas of Argentina.
Ground that stays frozen all year. Water cannot drain through it, so in summer the thawed top layer is waterlogged and gleyed, and soil formation is slow.
Podzols need a cool, wet climate with coniferous forest, which Africa does not have; even its highest mountains are too small an area.
Its chernozems have thick, black, humus-rich topsoil and plenty of calcium, built up under grassland in a climate with weak leaching; the land is flat and summers are warm, which suits wheat.
For example: latosols in the Amazon (as in the Congo Basin); desert soils in the Atacama or Australia (as in the Sahara); alluvial soils on the Ganges plain (as along the Nile); black clay soils on the Deccan (as in the Gezira).
33%. Any three of: erosion, salinization, compaction, acidification, chemical pollution.
Soil forms so slowly (hundreds to thousands of years) that soil lost now cannot be replaced in a human lifetime. Protection: terraces and contour ploughing, planting trees and grass strips, cover crops and mulch, adding manure, avoiding over-irrigation (any two).

1The main soils of the other continents

2Soils under pressure

The main soils of the other continents

Soils under pressure