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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.
@Iluviaporos - That's very true. I read in the paper the other day about a man who had been farming in a clay based soil for about ten years and his neighbors couldn't believe the size and quantity of the vegetables he was producing.
He said the secret was adding really good quality compost every year to the soil and digging it in well. He started out with a top soil layer that was only a few inches thick and tended to flood whenever there was a rain.
Now it's a couple of feet thick and drains very well.
It was really interesting reading about that kind of success and how with a little bit of work anyone can create that kind of loamy soil.
It gives me hope for my own soil which has quite a lot of clay in it.
Most of what you need to know about your soil you can tell with a few minutes of inspection.
As it says in the article, if you roll a ball of it between your hands and it sticks very tightly together and holds its shape, it's probably got quite a bit of clay and might become waterlogged easily. It might also need more nutrients.
If it falls completely apart and won't hold a ball shape at all, that means it probably has too much sand and will also need more nutrients.
If it holds a loose ball shape then it might be "just right".
In all cases, soil will usually respond well to adding organic matter, like compost. If you do this regularly every year eventually you won't know what to do with all the vegetables and other plants you grow, as they will thrive.