Development of a soil-model to simulate nitrous oxide emissions and application studies

Nitrous oxide is a greenhouse gas with a rather high global warming potential. A large part of anthropogenic nitrous oxide stems from forestry and agriculture where the usage of N fertilizers has continuously increased since decades globally. This increase in nitrogen-use has led to substantial nitrous oxide emissions indicated by increases in atmospheric concentration. Denitrification and nitrification are identified as the two major processes responsible for nitrous oxide emissions of soils. The production of nitrous oxide in soils is mainly dependent on the presence of certain microbes (denitrifiers and nitrifiers), the lack of oxygen and the availability of nitrate, nitrite, and ammonium. Denitrification is an aerobic respiration process and reduces mainly nitrate to molecular nitrogen through other intermediate nitrogen oxides. One of the intermediate products is nitrous oxide. Nitrification is a metabolic process and oxidizes ammonium to nitrite and nitrate under aerobic conditions. Under partly anaerobic conditions, however, nitrification can produce nitrous oxide. Thus both processes are depending on the oxygen availability in soils and on different physical and chemical soil attributes like moisture, pH, and temperature among others. In this project my scope is to write a simulation program that models denitrification and nitrification according to the current scientific reliable knowledge, using a new approach which is based on electron accounting and includes complex conditions of the soil like oxygen availability, texture of the soil, soil moisture and nitrogen-oxides and ammonium availability. The outcome will be compared with experimental data and studies. When evaluated, this new nitrous oxide model can be integrated in the in large scale simulation models to better trace N2 O formation in terrestrial ecosystems and agricultural systems under different climates and fertilizer regimes. In agriculture, certain farming technologies, such as the use of controlled-released fertilizers (precision farming), nitrification inhibitors, timing of nitrogen application and water management can lead to improvements in N-use efficiency and thus limit nitrous oxide formation. Results can be used to estimate the full life cycle analysis of e.g. bio-fuel plants and included in economic forecast studies to accomplish a more complete picture of greenhouse gas emissions in carbon dioxide equivalents.