The characterization of topsoils has recently received enhanced attention, particularly for environmental monitoring. Traditional national and international soil taxonomies hardly consider the topsoil in spite of its importance for soil quality. Consequently, the FAO “Topsoil Characterization for Sustainable Land Management” was developed to be used additionally for describing topsoils and to combine it with the “World Reference Base for Soil Resources” (WRB). In this paper, recommendations for a first step of a revision and expansion of the FAO “Topsoil Characterization” are made. On the one hand, common rules for soil description as used in the FAO “Guidelines for Profile Description” were incorporated in the FAO “Topsoil Characterization”. On the other hand, new characteristics for the description of the organic matter and of biological features of the topsoils were introduced. At first, the proposed German systematics of humus forms is presented and correlated with different national systematics, for validation in the international context. Secondly, a correlation of the new German systematics of humus forms with the FAO “Topsoil Characterization for Sustainable Land Management” and other topsoil systematics is made. Thirdly, additional qualifiers are described focussing on the organic layers and the biological features.
A coincidence between the characterization of humus forms and topsoils was found which appears to be an appropriate basis for the incorporation of humus forms in the FAO “Topsoil Characterization”. Investigations have shown that the topsoils in forests can be described comprehensively by additional qualifiers for the organic layers. Grassland or arable land which usually lack organic layers can be characterized in detail by qualifiers concerning soil biological activity in the A horizon. The methodology was already applied successfully in temperate regions. But there is still a need for further discussion of the revision and for tests in tropical and subtropical zones and poorly drained areas.
At the beginning of the 20th century municipal wastewater was used to fertilize grassland in the freshwater marsh of the river Weser. In 1987, 150 ha of the marsh became part of a mitigation area with artificial inundation during winter and spring. Heavy metal input may be expected from former wastewater treatment and artificial flooding nowadays. In addition, inundation may increase the availability of heavy metals that were accumulated during municipal wastewater treatment. In order to get an idea of heavy metal content and availability, the content of Cd, Cr, Cu, Ni, Pb, and Zn of the soil, the vegetation, and the input due to inundation were determined. Metal enrichment in the epipedon is evident for Cr, Cu, Pb, and Zn. Total content of Pb and Zn exceed the precaution limit. Soils treated with wastewater seems to contain more heavy metals than the ones without. Inundation causes an input of metals, but it is very low and varies in a broad range. Metal input is higher by atmospheric deposition than the one due to inundation. Degree of enrichment can be arranged in the order: atmospheric deposition > municipal wastewater >> inundation. In shallow ditch soils heavy metals are becoming more available.
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