Importance of Topsoil

The Dust Bowl era, when rampant soil erosion caused environmental devastation in America in the 1930s, drove home the importance of topsoil. It was a difficult and painful---even deadly---lesson in the life-giving nature of topsoil.

Nutrients

One important function of topsoil is supplying nutrients. This is a fairly complex process involving the formation of soil by weathering and plant decomposition over time. Topsoil supplies nutrients to plants and recycles nutrients by hosting the decomposition process of dead organic materials. Through invertebrate and microbial action, nutrients are recycled and become available to a new generation plants and other soil organisms. This occurs in topsoil in natural settings, such as forests, and also in cultivated settings, such as agricultural fields and gardens.

Structure and Support

Soil also forms the medium for the structure and support of plants. Everything from small plants growing in the understory of the forest---such a small wildflowers---to tomato plants and other garden crops to larger crops in agricultural fields and trees in a forest, depends on soil to support each plant's body. In every situation, plants develop root systems that grow into the topsoil, or deeper, to form a framework that supports their structure. Healthy topsoil is an integral part of this vital function.

Water

Soil is an intricate medium with organic and inorganic components. These components have varying abilities to bind moisture to the soil and keep it in a form that is available for plant growth. Topsoil---as contrasted with more mineral soil types such as subsoil---generally has organic components that increase the ability of the soil to retain moisture and make it available to plants. Very sandy subsoil, for example, lets water drain rapidly and does not retain enough moisture for the adequate growth of most plants.

Community of Organisms

Soil functions as a hosting medium for a wide array of organisms that can be beneficial to plants, neutral to plants or pathogenic. Topsoil is an important medium for beneficial organisms but is also a medium for pathogens that can be detrimental to plant growth.

Soil Stabilization

Indirectly, topsoil provides a buffer against soil erosion. Because topsoil can support plant growth, given enough rainfall a lush vegetative layer develops in the soil and binds the soil in place, preventing or reducing erosion that might otherwise be more severe if more mineral subsoils were exposed to the elements. In this respect, soil has a very beneficial, stabilizing effect by providing a buffer against soil erosion.

References

• University of Michigan
• University of South Dakota