N2O emissions result from de-nitrification processes in soils and in slurry on the farm. Most N2O emissions occur from soils after application of manure/fertilizer. The highest emissions are found when manure is applied with sod injection techniques (Velthof et al., 2003). The simplest way to reduce N2O emissions is to apply fertilizer to the soil surface, instead of injecting it into in the soil. However, these sod-injections techniques reduce NH3 emissions by about 30% relative to soil surface application. Here a trade-off between acidification and climate change is observed.
Presently only a small part of the nitrogen applied to the soil is actually taken up by the crop (at a maximum 70% but frequently values in order of 20% of the applied nitrogen are found - Meisinger and Randall, 1991). The nitrogen that is not taken up by the crop, nor is stored in the soil is lost to the surroundings, causing eutrophication as nitrate, acidification as NH3 or climate change as N2O. Better nitrogen management practices that increases the fraction of the nitrogen that is taken up by the crop seems the best route to go since all environmental themes benefit.
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