The agri-environmental indicators (AEI) of the Federal Office for Agriculture FOAG are intended to give early information on undesirable changes. They serve as a basis for further development of agricultural policies, for public information and for research. The AEI allow users to evaluate whether and how environmental goals can be achieved.
The National Soil Monitoring Network NABO calculates for about 300 AEI farms the annual copper and zinc balances, expressed for each individual farm and sampled site. Due to lack of reference values in the Swiss domestic legislation, the NABO element balances are compared with the so-called threshold loads of the German Federal Soil Protection Act to deduce information on the AEI «heavy metal balances». The threshold loads define the maximal element inputs that ensure an appropriate long-term soil quality.