In the atmosphere, ammonia reacts with nitric and sulphuric acid and produces low volatile salts. These can significantly contribute to particulate mass by either partitioning onto existing particles or building new particles. The acids are mainly produced from precursors arising from traffic, industry and households. In contrast, ammonia originates by about 90 % from agricultural sources. As ammonia is a very light molecule, it only contributes around 10 % of the particulate mass, but it is involved in the production of about 40 % of the particle mass. Therefore, ammonia emission controls appear to be an effective way to reduce particulate matter. However, there is no 1:1 relation between the reduction of ammonia emissions and the reduction of ambient particulate matter. The effectiveness is significantly reduced by two factors: firstly secondary inorganic aerosols only account for 40 % of total particulate mass and secondly the boundary layer air in Switzerland is over-saturated with ammonia. Our analyses demonstrate that a 10 % reduction of ammonia emissions only results in a 0.5 % decrease of particulate matter. Larger reductions are more effective, a 50 % reduction of ammonia emissions yields about a 3 to 10 % decrease in particulate matter.
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.