Seeding New Soil with Soil OrganismsIn nature, the accumulation of humus in soils is intimately associated with the development of a large and diverse assemblage of soil organisms that play important roles in decomposition and regulation of nutrient supply to plants, and in moderating pest and diseases in plants.[V2, V5, V10] Manufactured soils are especially low in such organisms. Recently manufactured composts will contain some of them, but lack many important species and groups of soil organisms.
Over time, diverse organisms will invade a new soil and an assemblage of soil organisms adapted to the particular site, usage and plants will develop. If the manufactured topsoil is placed over and/or mixed with an existing top soil, the existing soil will act as a source of organisms.
However, if the manufactured topsoil is placed over other types of subgrade which are largely sterile, the lack of a reservoir of diverse soil organisms close by could slow the development of a diverse community of soil organisms in the new soil. In such cases, soil organisms could be introduced by adding old soil from another site (e.g. a garden), or adding some 'well aged' compost or old manure that has been sitting around for a long time in contact with soil.
Any time topsoil is stripped from a site, it should be kept for this sort of use.
See also Section IV (Factors) Part 7 (Soil Organic Matter and Biodiversity in Manufactured Topsoils).
Page posted 17 May 2004
Modified 7 Mar. 2006