Agroscope FAL Reckenholz, Swiss Federal Research Station for Agroecology and Agriculture, Zurich

Inputs from diffuse sources in the Greifensee area: phosphorus and nitrogen

The phosphorus concentration in the Greifensee continues to exceed the target value, due to excessive phosphorus inputs. No relevant water pollution by nitrogen is currently evident. Phosphorus and nitrogen inputs from diffuse sources have been estimated with the aid of the Modiffus model. High phosphorus inputs are principally due to leaching of drained arable land, soil erosion from arable land and run off from grassland. High nitrogen inputs are the result of leaching and drainage losses from arable land. Further model calculations show the potential for reducing phosphorus pollution. Measures by farmers will not reduce phosphorus inputs sufficiently in the medium term to reach the target value for the Greifensee.

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