Getting Down and Dirty with Dirt, Part 1 - Soil Types

By Darcy Logan

A rose by any other name might still be a rose, but not all dirt is the same. There are basically five types of soil: clay, sand, peat, loam and silt. Most soils, including loam, are a combination of clay, sand and silt.

Where you live will usually determine the type of soil you find in your backyard. Soil that contains lots of clay can be found in Georgia and the Pacific Northwest. Yet in the Southwest, sandy soil is more common. In the Midwest, you are likely to find loam soil. No matter what type of soil you have, it can be improved by adding the right types of materials. But first you must understand what type of soil you are dealing with. Here is some basic information about each type of soil.

Clay
Clay consists of small particles (less than 0.002 mm in diameter). When dry, it has a smooth texture, although it is usually in the form of rock hard clumps. When wet, it is very sticky. Clay soil generally holds nutrients, but doesn't let air or water through. Its compact nature makes it very heavy and difficult to work. It is a good soil for growing vegetables and many flowers, including astibe, cotoneaster, hostas, mallow, roses and primula.

In clay, color matters. Red clay indicates good aeration and is a looser soil that will drain better. Blue and gray clays are tighter and will need to be loosened before they are capable of support growth. Soils can be loosened by working in lots of organic material (see below) or use the soil in raised beds to ensure that the soil drains better. Adding a mixture of coarse, sharp sand and crushed eggshells or powdered milk (for calcium) can also help the soil.

Sand
There is a reason they created sandpaper instead of clay paper - sand has a very rough texture. It is also the largest particle in soil (0.05-2 mm in diameter). It is usually light in color and dries out quickly. Basically, sandy soil is very small particles of silica and quartz, humus and a little bit of clay. The amount of humus, or natural compost, present in the soil will alter the color and the texture of the sand.

Sand is much easier to work with in comparison to clay, but does not hold moisture or nutrients well. Of all the major types, sand warms up quickest in the morning. Small plants with shallow roots will do well in this soil, including rosemary, lavender marjoram, oregano, sage, santolina, savory, thyme, coreopsis, impatiens, evening primrose, poppies, yarrow, sedums and some dianthus.

Silt
If silt were a bear, it would be the baby bear. It is not too large or too small, but somewhere in the middle (between 0.002-0.05 mm in diameter). Silt is smooth and powdery when dry, and smooth, but not sticky, when wet. It retains both nutrients and water better than sand, but not as well as clay. This means that silt will drain better than clay does. Silt is often found in rivers because the finer particles are washed downstream. Most plants will grow in silt. If the soil becomes too compacted, it can be improved by adding organic material (see below).

Peat
Peat soil is very rare and is at least 65 percent organic matter. It is heavy and highly acidic but low in nutrients. Dark brown or black in color, peat soil retains water and will have an almost spongy texture to it. Almost any soil can be made into peat soil simply by adding large quantities of organic material.

Loam
Loam soil is actually composed of two parts silt, two parts sand, and one part clay. It is often considered the ideal soil because it is ideal for most plants, including those that grow well in other types of soil. Loam soil is usually soft, dark, and crumbly. This soil drains well without loosing too much moisture and is generally rich in nutrients.

Continue to Part 2 >

© Doityourself.com 2006