Clay loam is a soil mixture that contains more clay than other types of rock or minerals. A loam is a soil mixtures that is named for the type of soil that is present in the greatest amount. The particles of clay are very small, which is one of its most important characteristics. For this reason, loams that contain a great deal of clay tend to be heavy, because they are so dense. While this soil type can be difficult to work with, it can also be improved to be a very good growing medium.
The density of clay is the cause of the two biggest drawbacks of clay loam. When it is very wet, it swells to retains water, which makes it difficult to work with. Over time, this poor drainage can also stunt plant growth. Dry clay shrinks but stays packed, forming dense clods and cracking the soil surface. These drawbacks can be lessened by adding organic matter over time.
Usually clay loam contains a good deal of plant nutrients and supports most types of plants and crops. Clay loams can be improved to create better drainage without too much difficulty. In some wet weather or climates, the drainage problems may be harder to overcome.
Probably the best way to improve clay loam is to regularly add organic matter in the form of compost or humus. Another good idea is to dig in more bulky matter, such as shredded leaves. This will help to keep clods from forming when dry. When wet, it will allow more water and air to pass through, leading to a less packed, better drained texture. As clay already contains a good deal of nutrients, improving the texture makes it a perfectly good soil mixture for most plants.
There are other methods that can be used to improve clay loam. One is to plant yearly in the same places. Old roots that are left behind will create extra space in the soil. Digging in plants that died on the spot will also help. It's often easier to dig clay in the fall, when the loam is drier. This can be done in the spring, but there may be fewer opportunities.
Clay soil can be identified by the fact that it is sticky when wet. Then it can be easily rolled between the fingers to form lumps or balls. These will retain their shape without crumbling.