Soil Types

Quick Review 1. What is the process that forms soil? - weathering 2. What are the two types of weathering? What causes them? - physical (rain, snow sleet, hail) - chemical (acids) 3. What is another name for a layer of soil? - horizon

More Review! 4. What is the name for soil that has a lot of decaying organic material? - humus 5. Which layer is most important for plant growth? - topsoil 6. What is the main cause of desertification? - improper management of soil which leads to erosion.

Types of Soils Soil is classified according to the type of mineral base and the size of the particles. Soil is classified according to the type of mineral base and the size of the particles. There are 3 types: There are 3 types:

1. Sand Very large particles Very large particles Feels rough Feels rough Does not hold water or nutrients well. Does not hold water or nutrients well.

2. Silt Particles are smaller than those in sand Particles are smaller than those in sand Feels smooth and powdery Feels smooth and powdery

3. Clay Has very small particles, and gums together. Has very small particles, and gums together. It holds water and nutrients well, but plants roots can’t grow well. It holds water and nutrients well, but plants roots can’t grow well. While it holds water well, it takes a long time for water to permeate a clay soil. While it holds water well, it takes a long time for water to permeate a clay soil. Brief, heavy rains may not reach plant roots. Brief, heavy rains may not reach plant roots.

Loam Mixture of sand, silt, and clay and organic matter. Mixture of sand, silt, and clay and organic matter. Water and nutrient holding abilities vary with composition. Water and nutrient holding abilities vary with composition.

Which type is best? The ideal type of soil for plant (crop) growth is partway between these two extremes. The ideal type of soil for plant (crop) growth is partway between these two extremes. Loamy soil has neither too small nor too large particles (It’s just right!) Loamy soil has neither too small nor too large particles (It’s just right!) Loamy soil has a good percentage of decayed plant material or humus which provide the nutrients that plants need. Loamy soil has a good percentage of decayed plant material or humus which provide the nutrients that plants need.

Further Resources National Resources Conservation Service website. Try out the Web Soil Survey tool to see what’s under your feet National Resources Conservation Service website. Try out the Web Soil Survey tool to see what’s under your feet National Resources Conservation Service National Resources Conservation Service US Environmental Protection Agency US Environmental Protection Agency US Environmental Protection Agency US Environmental Protection Agency Digging to China? Digging to China? Digging to China? Digging to China? Introduction to Soils Introduction to Soils Introduction to Soils Introduction to Soils