The Dutch soil policy is being focussed towards a more conscious and sustainable use of the soil, taking into account ecological, economical, and societal dimensions, as stated in the so-called 'Beleidsbrief Bodem' sent to the Parliament in December 2003. In the present report the framework for the determination of the sustainability of land-use as far as the ecological dimension and soil biodiversity are concerned is described. On the basis of a large database containing soil biological monitoring data and on the basis of ecological models for soil food-web stability, we derived two reference soil ecosystems indicating sustainable land-use, i.e. one for diary farming on sand and one for diary farming on river clay. Using mathematical evidence derived from field studies, a hypothesis is formulated to explain how soil organisms become affected by increasing effects of land management. This is discussed in relation to defining 'critical' conditions for ecosystem sustainability in agricultural soils: only within such stable assemblages, in fact, a host of soil organisms may interact in ways beneficial to each other. The approach provides a useful tool to assess land-use quality in the future.