The Differences Between Topsoil and Subsoil

Topsoil is the surface portion of undisturbed soil. It may be only an inch or so deep on thin mountainous land, or several or many feet deep in the river valleys and coastal plains. It is usually a darker color than the deeper subsoil because of it's higher organic content. Because of this relative organic richness, it is generally easier to handle than subsoil. It cultivates better, is less sticky or likely to cake. But with these advantages come some disadvantages--particularly the likelihood of weed seeds that accumulate in surface soil.
Subsoil is usually lighter in color, more sticky, less fertile and more difficult to handle. Typical are foundation diggings. Because such soil comes from a greater depth, it usually contains no weed seeds. For lawn making this advantage may be big and even outweigh the disadvantages. Subsoils are fairly easy to improve.

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