Main ecological risks are high nutrient inputs and accumulation of nutrients in soils. Beside the chemical risks,
soil degradation occurs as a result of pigs’ behaviour and farm machinery. The ecological risks mentioned may lead to
ecological effects like an increase of nutrient leaching into groundwater and its pollution. Eutrophication of surface
waters as a result of nutrient output, with surface runoff from paddocks and increased soil erosion, because of reduced
infiltration rates and a reduced filter function of the soil for elements and micro-organisms, are further ecological effects
resulting from intensive outdoor pig fattening.
The potential for N leaching primarily results from the management of outdoor pig production, either from too
intensive farming systems (Williams et al., 2000), when stocking rates are too high, or from increasing nutrient
concentrations at the installation units. Stauffer et al. (1999) found the leaching potential to be 20 times higher in front of
the huts than in the main pasture area. The ecological risks of N pollution from outdoor pig production depend on the Nsources, their forms and their distribution on paddocks. They are summarised in Table 1 for their ecological relevance with
respect to outdoor pig production