What Is the Difference Between Topsoil & Loam?

Is topsoil loam, or is loam topsoil?

Comparing topsoil to loam is a little like comparing east and west to thin and thick. One set of words describes direction and location, and the other is a set of physical qualities. It's the same with these two soil classifications.

Topsoil

Topsoil is just what the name implies. It's the top layer of soil in a landscape, according to the University of Connecticut Home & Garden Education Center. The name refers to the location of this particular layer of soil in a yard, garden or other landscaping project.

Loam

Loam is a term that refers to the combination of particles within the soil. Some experts may disagree about what makes a good loamy soil, but, in general, a good loam is generally one that's almost equal parts sand, silt and clay.

Types

You might have a loamy topsoil in your yard. It may have more of one particle than another. So it might be classified as clay loam, sandy loam or silt loam. Or it can be a combination. For example, a loam could be classified as a sandy clay loam or a silty clay loam.

Misconceptions

The terms topsoil and loam can be confusing because they're sometimes used interchangeably.

Considerations

Many garden books often refer to loam as the perfect gardening soil, but they're also referring to the mixture of particle sizes and organic matter. Topsoil--because of its location--is where you do most of your planting. So it should be the ideal gardening soil, too.

Identification

Still confused? Just think of loam as the particle quality of any soil, whether it's topsoil or not.

References

• Purdue University Consumer Horticulture: What is Loam?; B. Rosie Lerner; Jan. 6, 2000
• University of Connecticut Home & Garden Education Center: Purchasing Topsoil; Dawn Pettinelli and Dr. Harvey D. Luce

Resources

• The New York Times: Garden Q & A-Topsoil vs. Loam; Dora Galitzki; Feb. 20, 1997