Remedy for Compacted Soil

Soil Compaction

• Soil is compacted when the pores are tightly pressed together, inhibiting the movement of air and water. This state is desirable for structures that require a stable base, such as buildings and pavement. But soil compaction is a serious obstacle to plant growth. Excessive soil compaction is harmful to plants in two ways. It limits plant growth by preventing plant roots from penetrating the soil, and it decreases drainage.

Soil Amendments

• Adding organic matter, such as compost and peat moss, can reduce soil density to a point where plant growth isn't limited. About 25 percent of the volume of compacted sandy loam needs to be amended with organic matter to decrease the density so that drainage and aeration is improved. For heavy clayey soils, at least 50 percent of the volume needs to be amended to make any difference. Dig in the organic material to a depth of at least 18 inches.

Sand

• Sand can be added to compacted soil to increase the density and improve the drainage, but about 75 percent of the area has to be amended this way. Make sure the sand has uniform, large particles. Sand needs to be tilled into the soil to a depth of 18 inches to 36 inches. For a large site, this method is impractical. The best way to amend soil with sand is to mix it with material off the site, essentially bringing in new soil.

Soil Replacement

• Soil replacement might be a solution if the area isn't large. For trees and shrubs, at least 18 inches of topsoil is needed. An alternative option is to bury the compacted material with better soil. This measure can be incorporated with site design that creates areas for berms, or planned landscape areas. Topsoil for berms and planted areas should also be to a depth of at least 18 inches; 3 feet is best.