Topsoil is the upper, outermost layer of soil. It has the highest concentration of organic matter and microorganisms and is where most of the Earth’s biological soil activity occurs.
Plants generally concentrate their roots in and obtain most of their nutrients from this layer.
A variety of soil mixtures are available commercially as topsoil, usually for use in improving gardens and lawns. Another important yet not commonly known use for topsoil is for proper surface grading near residential buildings such as homes. "The ground around the home should slope down six inches for the first ten feet away from the home. This can often be done by adding topsoil (not sand or gravel)."
