Soil Orders

• Climate. Soils are variable with the climates they are in. Climate involves both temperature and moisture, leading to varying levels of weathering or soil leaching. Wind and dryness affect how soil gets distributed. Seasons that are cold will have less chemical weathering.

• Topography. Slope of the land affect how much moisture it gets and what the soil temperature of the soil might be. Those slopes that are sunnier have a different erosion rate than those not facing the sun. Steeper soils might be thinner due to the effects of gravity.

• Biological aspects. The plants, animals, and microbes in an area affect the soil.

Human activity also affects it. Plants with deep roots will loosen soil. Different types of roots will affect the soil differently. Microbes interact intimately with roots in certain ways that are often symbiotic.

• Time factors. Soils mature over time and reflect the area's activities. You need to know that soil formation is ongoing and completely continuous throughout time.

Buried soil must essentially start over as a new soil type with features seen in most deeper soils.

SOIL ORDERS

As mentioned, soil is divided taxonomically into orders. The highest level has 12 different orders, but there are 64 sub-orders among these. It gets even more complex with 300 groups and 2400 subgroups. Let's look at a few of the major orders and talk about what they might look like:

1. Alfisols – these soils are in moist to semi-arid areas. They were once formed in forests or with overlying vegetation, making them productive for crops.

2. Andisols – these are the most productive soils. Found with moderate to high rainfall and cooler areas, you will see these with volcanic materials.

3. Aridisols – these are mostly too dry for most plants and have things like salt and calcium carbonate that get leached out if it is too wet. This is desert soil.

4. Entisols – this is soil where erosion or decomposition is fast – too fast to make new soil. You'll see the parent material here in slopy areas, dunes, or along flood plain regions.

5. Gelisols – these are soils in cooler areas or in higher elevations where permafrost is located near the surface. Ice churning and frost churning can happen here.

6. Histosols – this is highly organic soil with no permafrost. It is extremely wet here in places like mucks, bogs, or moors.

7. Inceptisols – these are areas in mixed environments with moderate weathering seen in many climates.

8. Mollisols – these are dark soils with a lot of organic material. The soil provides a rich base so it is very fertile soil.

9. Oxisols – these are tropical and subtropical soils that are very weathered and stable. They have naturally low amounts of fertility and do not retain fertilizers well.

10. Spodosols – these are weathered soils where organic material and aluminum are stripped out into the subsoil so the soil itself isn't very fertile. The soil is very acidic.

11. Ultisols – these are soils in humid parts of the world that are also acidic with just a few inches of nutrient-rich soil. They do not retain fertilizers well.

12. Vertisols – this has a lot of clay in it that expands with moisture. These do not transmit water easily so they don't leech and are naturally fertile soils.