Topsoil Facts

Topsoil Facts image by DRW & Associates Inc, Microsoft Office clip art
Topsoil Facts image by DRW & Associates Inc, Microsoft Office clip art


Topsoil is where grass and flowers grow, but it's one of the most vulnerable parts of the environment. Conserving---and restoring---viable topsoil is essential to commercial and residential landscaping as well as to agriculture.

Topsoil has developed over millions of years


Topsoil is rock that has been broken down by the earth's geological processes and pushed up to the surface where it mixes with decaying plant and animal matter.

Topsoil provides a hospitable environment for seeds and plant roots.


Humus and nitrogen in topsoil provide nutrition for plants and provide filtration media for water in aquifers.

Not all topsoil is black---local mineral deposits may make it brown or reddish.


Topsoil varies from about 2 to 10 inches deep. High levels of organic matter give it a darker color than sub-soils and it contains fewer salts, less clay and other materials that might limit plant growth. It has few fragments of coarse rock and contains nitrogen, phosphorus, potassium and iron.

Grass clippings supplement the nitrogen in topsoil.


Good topsoil allows water to drain easily, but it holds water long enough for roots to use it. Unlike clay or rocky sub-soils, its texture allows easy penetration by plant roots.

Lawngrass fades but weeds thrive on thin or clay-heavy topsoils.


Ideal topsoil has a pH between 5.5 and 7.5, contains high percentages of sand and silt, a low percentage of clay and 2 percent or more organic matter.

Erosion along riverbanks may deposit topsoil downstream or fill marshes.


Topsoil lost during development excavation or removed by flooding and erosion must be replaced for soil to support plant growth. Topsoil should always be tested before adding amendments or fertilizers.


  • Soil Facts
  • King County, Washington; Preserving And Restoring Healthy Soils
  • Definitions for Topsoil

Who Can Help

  • Utah Topsoil Quality Guidelines
  • Buying Topsoil
Keywords: topsoil, environment, grass, agriculture, landscaping

About this Author

Laura Reynolds began writing professionally in 1974. She has worked as author and editor in nonfiction, professional journals and newspapers. Reynolds has also served in numerous appointed and elected local offices. She holds a Bachelor of Science in education from Northern Illinois University.

Photo by: DRW & Associates Inc, Microsoft Office clip art