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.
Symbiotic nitrogen fixation by bacteria in the soil coexisting with legumes leads to reduced fertiliser requirement. It is not easy to measure this variable on farms, however. Now researchers from Agroscope have developed a method for estimating nitrogen input via symbiotic fixation at farm level.
With increasing global and regional temperatures, even in Switzerland the growing season has lengthened considerably. Using data from the Federal Office of Meteorology and Climatology, Agroscope has traced the development of the growing season since the start of the previous century.
The phosphate mineral reserves required for fertiliser production could be exhausted on a global scale in just a few decades. This study presents a method for recycling a Swiss industrial by-product into a phosphate fertiliser.