To study and investigate soil biodiversity is a difficult task because of the complex interactions that exist in soil and the need for considerable expertise to undertake the necessary investigations. The factors that influence biodiversity are diverse: some are natural, for example soil acidity, water retention, temperature and organic matter content, others are anthropogenic, for example human population pressure. This report summarises the results of the multidisciplinary BIO-BIO study of biodiversity and bioindication, conducted within the Pavia Project, which had as its principal objective the evaluation of the quality and health of soil in Pavia Province, Lombardy, in northern Italy. The area under investigation covered 3000 km2 and the project took into account of the different uses of soil. International standard methods were adopted for the identification of sampling points, the collection, treatment and analysis of the samples for heavy metals, macro-elements, dioxins, furans, soil acidity, physical properties (water retention, pore size, geochemical profile, etc.) and biological data (bacteria and terrestrial mosses). The differences in soil biodiversity that have resulted from different management practices, namely: organic or 'biological' farming; conventional 'manure' farming using animal excreta and mineral fertilizers; and sewage sludge 'amended' applications to soil, have been studied on a seasonal basis (4 sampling per year) and analysis of soil samples taken at 0--5 cm; 0-15 cm and 15-30 cm depth. Some general ideas of what needs to be done in this field are outlined, whilst, at the same time, suggesting the basis for further studies. Bacteria, collembola and earthworms, which cover the three nutritional nets, are the most useful bio-indicators for appraising the evolution of biodiversity and assessing soil quality. To evaluate the biodiversity 'in soil' means to appraise the quality of the soil. Only integrated studies, that take into consideration the chemical, physical and biological nature of soil, will lead to a full understanding of soil biodiversity.
