Nitrogen and phosphorus balances of Swiss agriculture between 1975 and 1995 Are outdoor pigs a groundwater hazard?

The nutrient balances of the Swiss agriculture were calculated for nitrogen (N) and phosphorus (P) for all the years between 1975 and 1995 on the basis of the farmgate balance, a comparison between nutrient input into agriculture and output from agriculture. Nitrogen surplus amounted to about 124‘000 t N and 116 kg N/ha agricultural used area (= surface used by agriculture without alpine pastures) respectively in 1995. For phosphorus the corresponding values were about 13‘500 t P and 13 kg P/ha. Between 1975 and 1995 mineral fertilizer consumption increased at first and decreased subsequently. A strong decrease over the whole period was observed for the imported feedstuffs. Nutrient surplus increased for both nutrients up to 1980, then decreased continuously. In the framework of the evaluation of the ecological measures according to the Agricultural Law a decrease in nutrient surplus of nearly 10‘000 t N and about 5‘500 t P could be observed between the reference years of 1990-92 and 1995.