Influence of soil properties on the release of dissolved organic matter (DOM) from the topsoil

A percolation experiment over a period of three month with small monoliths from forest and grassland:soils varying in their anthropogenic changes wa carried gut to identify, to weigh and to quantify important soil properties for DOM release from the topsoil. Quality of soil organic matter determines the amount of DOM released from the topsoil if the soils have a low ability to adsorb and to precipitate DOM. Favorable conditions for high DOC concentrations in the soil solution are wide C/N ratios in the soil and in the hot water soluble fraction, a high soil content of hot water soluble organic carbon and a high portion of hot water soluble organic carbon in the total organic carbon content. Anthropogenic changes of the Soils are effective to DOM release via changing quality of soil organic matter. Long dry periods : and large water fluxes can further increase DOM release. The effects of soil organic matter can be disguised in soils with a high DOM retention capacity (high CEC, high content of exchangeable bases, Fe-ox and Fe-d). Then adsorption and precipitation determine DOM release from the topsoil and contribute;to a decrease of DOM release.