13.9: Types of Soils
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Where would you rather grow crops?
The soil on the left is in Tuscany in Italy. Tuscany is known best for growing grapes for wine and olives for olive oil. The soil on the right is in China. It is the soil that remained when rainforest trees were removed. Do you know which soil would be better for crops?
Types of Soils
For soil scientists, there are thousands of types of soil! Soil scientists put soils into very specific groups with certain characteristics. Each soil type has its own name. Let’s consider a much simpler model, with just three types of soil. These types are based on climate. Just remember that there are many more than just these three types.
One important type of soil forms in a deciduous forest. In these forests, trees lose their leaves each winter. Deciduous trees need lots of rain — at least 65 cm of rainfall per year. Deciduous forests are common in the temperate, eastern United States. The type of soil found in a deciduous forest is a pedalfer (Figure below). This type of soil is usually dark brown or black in color and very fertile.
The soil beneath a deciduous forest is a pedalfer. These soils are very fertile.
Pedocal soil forms where grasses and brush are common (Figure below). The climate is drier, with less than 65 cm of rain per year. With less rain, there is less chemical weathering and organic material, and the soils are slightly less fertile.
Grassland soils are less rich than soils in more humid regions.
A third important type of soil is laterite. Laterite forms in tropical areas. Temperatures are warm and rain falls every day (Figure below). So much rain falls that chemical weathering is intense. All soluble minerals are washed from the soil. Plant nutrients get carried away. There is practically no humus. Laterite soils are often red in color from the iron oxides. If laterites are exposed to the Sun, they bake as hard as a brick.
Laterite soils, which are found beneath rainforests, are not good for growing crops.
- Pedalfer is the soil common in deciduous forests. Pedalfer is dark brown and fertile.
- Pedocal is the soil common in grasslands. The more arid climate increases calcium in the soil. Pedocal is not as fertile.
- Laterite forms in tropical rain forests. Chemical weathering strips the soils of their nutrients. When the forest is removed the soil is not very fertile.
- What is pedocal? How much chemical weathering leads to this soil type and why?
- What is the plant life found with pedocal soils? How much organic material do they contain?
- What is pedalfer? How much chemical weathering leads to this soil type and why?
- What is the plant life found with pedalfer soils?
- What is laterite? How much chemical weathering leads to this soil type and why?
- What is the plant life found with laterite soils?
- If a forest is leveled so that a laterite soil is exposed to the Sun, what happens to it?
Use the resources below to answer the questions that follow.
- What is laterite?
- Where is it found?
- What zones are in laterite? What process or lack of that process produces each zone?
- How does an ore body with a high amount of metals form in these soils?