What Is Topsoil?

Overview

Rutgers University's cooperative extension specialist says topsoil is "the top 6 to 10 inches of soil or the depth to which the soil is ... cultivated." For most of us, it is what supports the plants we grow.

Topsoil supports the plants we grow. image by "The Garden Floor" is Copyrighted by Flickr user: frozenchipmunk (Sharat Ganapati) under the Creative Commons Attribution license.

Identification

Soil is the rocky base that has been pulverized and pushed upward to the planet's surface over time. Topsoil is the most finely ground top layer and contains organic matter from decaying surface life.

Types

All soils are combinations of particles. The largest are called sand, then silt, then the smallest of particles, clay. Whichever type of particle predominates gives a soil its "type."

Function

Sandy soil holds few nutrients---it needs some silt and clay to help. Soil with too much clay holds too much water and becomes soggy---it needs sand and silt to hold oxygen and nitrogen between particles to allow proper drainage.

Balance

A balance of from 40 to 65 percent sand, 25 to 60 percent silt and 5 to 20 percent clay makes a "friable" soil base for a garden or lawn base.

Organics

Topsoil contains the remnants of millions of years' worth of dead plants and other decayed matter. They add carbon, oxygen, nitrogen and other nutrients to the minerals from the original rocks.

Additiions

Lime, sulfur, composts and fertilizers containing nitrogen, phosphorous and potassium are used to correct acidity, texture or fertility of topsoil.

References

  • Topsoil for Landscape Use
  • Organic Matter in Soil

Who Can Help

  • Purchasing Topsoil
  • UN Food and Agriculture Organization Report on Topsoil for Sustainable Land Management
  • Soil Types
Keywords: topsoil, soil, plants, cultivate

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.