Ammonia (NH3) volatilization
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The sensitivity of ammonia (NH3) volatilization in agricultural production systems to variation in input parameters was investigated by Bouwman et al. (2006). Various parameters were selected, including nitrogen excretion per head, animal stocks, the distribution of production over pastoral, and mixed and landless systems, fertilizer inputs and the NH3 emission factors for animal housing, etc. The results suggest that on the global scale, excretion of nitrogen per head and animal stocks are the most important parameters in the model. However, the importance of the various parameters varies among world regions and countries. For example, in China fertilizer use is a far more important determinant for total ammonia loss than in other world regions, while in India the use of manure as fuel is a very important process. The overall conclusion is that nitrogen excretion per head merits our attention in future research. Research will focus on the difference between N excretion in extensive versus intensive systems, and modelling excretion as a function of production characteristics such as milk production per head and nutrient intake by feed category. This study also made clear that the spatial modelling of nutrient use allows for analysis of various policy alternatives and consequences for the nitrogen cascade. |
