Introduction and background
The application of organic matter to ecosystems has received increasing attention in many
European countries in recent decades. This is due not only to the potentially beneficial effects of
organic matter application, but also to the increasing availability of cheap sources of organic
matter, such as sewage sludge and compost in industrialised countries. Within the European
Community, a total of 7,432,000 t of sewage sludge dry matter was produced in 1996. This
quantity is expected to increase by 35% by the year 2005 (Vetterlein & Hüttl 1999). A similar
situation exists for compost. With regard to the sustainability concept in Germany a matter cycling law was established in 1996, indicating that all waste material suitable for reutilization such as sewage sludge and compost, e.g. via application in agriculture, must in fact be reutilized and only those waste materials that can not be beneficially used e.g. for soil improvement purposes should be disposed on dumps or used for energy production. Also based on the sustainability concept, a few years later the German government passed a soil protection law, indicating, that soils should not be harmed by whatever management practise. As the application of organic waste materials such as sewage sludge and compost may not only have positive effects but may also cause ecological risks such as soil contamination with heavy metals or eutrification problems due to the input of high rates of N and P contained in these materials, clearly between these two regulations a conflict was produced. This controversial discussion has lead to the suggestion that in Germany specific types of application of organic matter, particularly of sewage sludge and compost for agricultural purposes, should be discontinued. Hence, with regard to the ecological effects of organic matter management, the question arises whether application of organic matter aiming at soil improvement can be seen as a contribution to the sustainability goal or not.