This article, written by Thomas Bolles of the Prince William Unit of the Virginia Cooperative Extension, follows up on Field Notes (Vol. 19, No. 5) and provides additional information specifically for homeowners on how soil amendments can be implemented on residential lawns. The following recommendations are based on Virginia Cooperative Extension guidelines to help establish and maintain a healthy turf.

Tillage and Soil Testing for New Lawns

The optimal time to amend soil is prior to the establishment of a new lawn, before anything is planted in the soil. Ideally, tillage and amendments should be preceded by a soil test to determine the fertility and pH of the soil so that the appropriate amount of lime and fertilizer can be added during tillage. To determine the correct amount of lime and other fertilizer, homeowners are encouraged to contact the Virginia Cooperative Extension.

Research from Virginia Tech and other land grant universities suggests that, for residential lawns in urban areas, soils should be tilled to a depth of 4-6 inches. Amending the soil with two inches of compost while tilling will allow the amendments to be incorporated quickly and uniformly. In addition, this has been shown to significantly increase the rate of turfgrass establishment.

Compost will increase the soil's organic matter content, which reduces compaction, improves the soil's ability to infiltrate water, and nourishes beneficial microorganisms. Less compaction means additional pore space for roots to move through, as well as more space for air and water to penetrate.

Recommendations for Established Lawns

Once a lawn is established, it is much more difficult to incorporate organic matter into the soil, when removing the turf is not always practical. As a result, Virginia Cooperative Extension recommends top-dressing established lawns annually with ¼ inch of compost; this will help maintain a rich, healthy soil. (While adding more compost is beneficial, cost is usually a limiting factor.) Core aeration in conjunction with top-dressing will speed the process of incorporation into the soil.

Building the soil will improve its ability to infiltrate water and ultimately help filter runoff and trap sediments. A healthy, well-maintained turf lawn will also require fewer chemical inputs. Properly amending the soil under the lawn is a win-win for homeowners by improving the look of individual landscapes and helping to protect the water quality of our waterways.

For more information on Virginia Cooperative Extension recommendations for soil amendments, please contact Thomas Bolles.

For additional information on how soil amendments relate to BMP credits, please contact Jennifer Brophy-Price or Bethany Bezak.

¹ Soils in Virginia are typically acidic, meaning they have low pH. Since many nutrients in the soil become unavailable at low pH; lime is often used as a soil conditioner to counteract the acidity. A soil test will provide lime recommendations based on the soil’s ability to maintain a target pH.
² While the focus of this article is geared toward homeowners with residential lawns, it should be noted that depending on the area of amendment and the impervious cover of the contributing watershed, the addition of 2” of compost during tillage may also qualify for Best Management Practice (BMP) credit under the recently-adopted Virginia Stormwater Management regulations (based on the Virginia Stormwater BMP Clearinghouse; Specification No. 4 Soil Compost Amendments).
³ However, it should be noted that while top-dressing established lawns with compost will benefit the soil, this practice will not provide BMP credit under the recently-adopted stormwater management regulations.