This document would evaluate the habitat function of soils by determining effects of soil contaminants and substances on organic matter decomposition. This test is applicable to natural soils and soil materials of unknown quality (e.g. contaminated sites, amended soils, soils after remediation, agricultural or other sites under concern). In this method, the effects of individual substances can be assessed using standard natural soil used in chemical-spiking testing. For contaminated soils, the effects are determined in the test soil and in a control soil. In this laboratory method, sterilized filter paper disks are used as a source of organic matter. Organic matter decomposition is estimated based on the mass loss of filter paper disks sandwiched between two layers of the test soil. Information is provided on how to use this method for testing substances under temperate conditions. This document is not applicable to substances for which the air/soil partition coefficient is greater than 1, or to substances with vapour pressure exceeding 300 Pa at 25°C. NOTE – The stability of the test substance cannot be ensured over the test period. No provision is made in the test method for monitoring the persistence of the substance under test.