What Are Four Types of Soil?

Soil is the "unconsolidated mineral or organic material on the immediate surface of the Earth that serves as a natural medium for the growth of land plants," according to the Soil Science Society of America. Soil is categorized based on a number of factors, including its color, moisture level, structure, texture and pH. There are four primary categories of soil.

Sandy soil is light and airy, which allows plenty of oxygen to move through it, but it lacks in nutrients, making it less than ideal for growing. Since it is so light and drains easily, it does not retain nutrients and becomes very dry, which prohibits plant growth. Sandy soil has a rough texture.

Clay soil is a dense, extremely compacted type of soil; the soil's density makes it difficult for oxygen to pass through. It is on the opposite end of the spectrum from sandy soil, since it retains nutrients very well, but its density prevents the plant roots from accessing those nutrients for growth. Clay areas of soil become very wet, because the water cannot penetrate successfully. It has a smooth texture when dry, but the top layer of the clay gets sticky when wet, because the water pools on the surface rather than being absorbed by the clay. Clay's lack of ability to absorb water also causes runoff.

Silt soil is in between sand and clay soil in consistency. It is heavier than sand, but lighter than clay. It is commonly found near streams and rivers because the particles move with water without effort. Its texture has a tendency to become crusty, making runoff common, since it cannot drain efficiently.

Loam soils are the best type of soil for gardening and general plant growth. Loam soil is generally composed of from 25 to 50 percent sand, 30 to 50 percent silt and 10 to 30 percent clay, depending on the surrounding soil types. Loam is very easy to work with, holds nutrients well and is able to retain enough water for plants to grow efficiently.

Collect a sample of approximately ? cup of the soil in the area you are testing. Place the soil sample in a jar along with 2 cups of clean water. Shake the jar for one minute. Wait one minute and make a mark on the side of the jar where the sand has settled, on the bottom. Wait an hour and mark the jar at the next level, which is the silt layer. Wait 24 hours and the clay layer will have formed on the top. Determine your soil type based on the amount of each type in your jar.