Evaluation for Topsoil

Source of Topsoil

Construction activities require the movement and placement of soil materials. Topsoil is used to cover either a disturbed or undisturbed area so that vegetation can be established and maintained on the site. In the soil judging contest, the upper 40 inches of the soil profile will be evaluated for use as topsoil. The surface layer or the A horizon of most soils is preferred for topsoil because of the organic matter content. This layer must be sufficiently thick for cost-effective removal and use as a topsoil material. Organic matter increases the absorption and retention of moisture and nutrients for plant growth, enhances structural development and stability of soil aggregates, and provides a more favorable soil tilth quality than occurs in soils low or very low in organic matter content. Soils suited for a source of topsoil generally have more than 40 inches of total soil profile depth, have textures in the medium textural group, have dark or black A horizons greater than 14 inches thick, and are somewhat poorly or better drained in their natural internal drainage class. These soils are free of stone and cobbles and have little or no gravel. Soil properties listed in table 5 will be used in the contest to determine whether the material is suitable for use as a source of topsoil. Presence of redox features at or below 12 inches of the surface will be used to determine evidence of a water table. Rust colored redox features are usually visible if a seasonal high water occurs within the upper 12 inches of the black A horizon. These redox features may be few in quantity. Poorly and very poorly drained soils have limitations for this use. The properties listed are not inclusive for making an overall evaluation as to the suitability for a source of topsoil material.