Soil type facts for kids

A soil type is a way to group soils that are similar. Think of it like how scientists group animals or plants! All soils that share certain features belong to the same soil type.

Soil types are part of soil classification. This is the science of sorting soils into different categories. Every soil on Earth fits into a specific soil type. While soil types are ideas we use to understand soil, you won't find a "soil type" sitting in a field. Instead, you'll find actual soil that belongs to a certain type.

What Are Soil Types?

In most systems that classify soil, soil types are found at the middle or higher levels. A soil type can often be broken down into smaller groups called subtypes. Also, several soil types can be combined to form even bigger groups.

How Are Soil Types Defined?

Scientists define soil types using different features. Some systems look mainly at how the soil was formed. This is called pedogenesis. An example of this is the German soil system.

Other systems use a mix of features. They look at how the soil formed and also at features it got from the original rock or material it came from. The World Reference Base for Soil Resources (WRB) and the USDA soil taxonomy are examples of these systems. Some systems, like the Australian Soil Classification, simply look at the soil's properties, no matter how they got there.

Using Soil Layers to Define Types

One easy way to define a soil type is by looking at its soil horizons. These are the different layers you see when you dig down into the soil. However, this isn't always possible. Some very new soils might not have clear layers yet.

For other soils, it's easier to define the type by looking at features common to the whole soil. For example, the WRB system defines Arenosols by how much sand they contain.

Human Impact on Soil Types

Many soils are changed by human activities. This is why many soil types in different classification systems include how humans have affected them. For instance, a soil type might be defined by how much it has been farmed or built upon.

Different Ways to Classify Soil

Because "soil type" is a very general term, many soil classification systems don't use it directly in their names.

The USDA soil taxonomy, for example, has six levels for grouping soils. These levels are called:

• Order
• Suborder
• Great group
• Subgroup
• Family
• Series

The WRB system calls its first level "Reference Soil Group." For the second level, they add extra descriptions called "qualifiers." They don't use a special name for the combination of the Reference Soil Group and its qualifiers.