How Much Topsoil Does Grass Need?

Topsoil refers to the topmost layer of ground. Some topsoil is highly fertile, with years of accumulation of rock and decaying organic material. The required depth of topsoil differs by plant. Lawns have a specific topsoil depth requirement.

Depth Recommendation

"Garden Wisdom & Know-How" author Judy Pray recommends at least 4 inches of good topsoil to ensure optimal growth of grass roots. Kimberly Willis, writing in "The Complete Idiot's Guide to Country Living," also recommends using at least 3 to 4 inches of topsoil for healthy lawns.

Requirement

Topsoil is usually not required in established lawns. In new areas, where lawns are being established from scratch, the addition of topsoil is necessary. Grounds around newly constructed homes sometimes have topsoil removed at construction time. You would also need topsoil if you change the elevation of the lawn for better drainage or for aesthetic reasons.

Alternative

Pete Landschoot, Penn State University turf extension specialist, recommends using compost as the best alternative to topsoil. Compost is usually readily available and is also a more economical source of organic matter. Even in areas where topsoil is not required for grass, adding compost works as a soil amendment that leads to better grass health. This is especially beneficial in clay soils at it improves aeration and drainage.

References

• Washington State University Extension; Gardening in Western Washington; Steve Witcher; 1996
• "Garden Wisdom & Know-How"; Judy Pray; 2010
• "The Complete Idiot's Guide to Country Living"; Kimberly Willis; 2008
• The Connecticut Agricultural Experiment Station; Starting a New Lawn; Thomas M. Rathier; April 2004
• "Turfgrass Maintenance Reduction Handbook"; Doug Brede; 2000