INDICATORS OF THE SUSTAINABILITY OF HEAVY-METAL MANAGEMENT IN AGROECOSYSTEMS

The aim of sustainable heavy-metal management in agro-ecosystems is to ensure that the soil continues to fulfil its function in agricultural production, in environmental processes such as the cycling of element s, and as a habitat of numerous organisms. Assessment of sustainabilit y has to be carried out in time, since metal accumulation in soil is l argely irreversible and may cause problems if certain concentration le vels are exceeded. In this study, we provide a concept to assess the s ustainability of current metal cycles in agro-ecosystems based on dyna mic heavy-metal balances for the plough layer. After presenting some g eneral aspects of dynamic metal balances, we introduce 'sustainability indices'. These characteristic numbers can be used as indicators for potentially adverse effects of current agricultural practices, since t hey account for (ecotoxicologically founded) soil quality standards an d for quality standards for produce, groundwater and surface water. Th ey can also be used to assess the effects of different management opti ons that aim to prevent quality standards from being exceeded as they provide insight in the dynamics governing input-output relationships. This is illustrated with a case study on heavy-metal flows in differen t arable farming systems. (C) 1997 Elsevier Science B.V.