Nitrogen, phosphorus and potassium balances and cycles of Swiss agriculture from 1975 to 2008

Intensification of Swiss agriculture after 1950 led to an increase in productivity and a range of environmental and health problems provoked by growing inputs of nitrogen (N), phosphorus (P) and potassium (K) into the agricultural cycle. In 2008, farm-gate balances showed surpluses of 108 kg N ha(-1), 5.5 kg P ha(-1) and 28 kg K ha(-1) for Swiss agriculture. Nutrient surpluses rose between 1975 and 1980 and then decreased significantly until 2008, with percentage reductions being higher for P (80%) and K (54%) than for N (27%). The introduction of direct payments for ecological programmes such as integrated production in 1993 led to a more pronounced decrease in nutrient surpluses for several years, until most farmers had joined these programmes. Lower surpluses could primarily be attributed to reductions in mineral fertilizer use and N deposition. Biological N fixation and atmospheric deposition contributed most to the uncertainty in calculating nutrient balances. N cycle was characterized by substantial inputs into and outputs out of the agricultural sector, whereas P and K cycles were more closed. In future, nutrient balances at a regional level are required to identify areas with high surpluses. In Switzerland, a further reduction in surpluses could be achieved by better feeding strategies and an improved fertilizer management, mainly of animal manure.