The influence of redox dynamics on nitrogen cycling and nitrous oxide emissions from soils

Understanding the role of the nitrogen cycle in soil systems is of importance in many environmental applications (for example, minimizing greenhouse emissions). Soils are a dominant source of nitrous oxide N2O releasing an estimated 9.5 Tg N2O -N year-1 (65% of global emissions according to IPCC, 2001a). Further research is still needed to comprehend key drivers of N2O emissions from soils and its influencing factors. Amongst these factors, water content can be considered a crucial one since it modifies the ratio of N2O - N2 emissions and influences the rate of oxygen supply thus determining whether aerobic processes such as nitrification or anaerobic processes (i.e., denitrification) becomes dominant within the soil. Also, water content is linked to dissolved oxygen and to redox potential, which regulate microbial metabolism and chemical transformations in the environment. Investigating the interplay between these physical and chemical factors is needed to comprehend the nitrogen cycle at the catchment scale. The importance of soil moisture in the nitrogen cycle has already been investigated, however only few works are focusing on water content dynamics. To our knowledge, there are no studies that investigate N-emission under realistic rain conditions as well as linking soil moisture dynamics to nitrate ammonification (also known as DNRA) along the soil profile. The purpose of this study is thus to analyze if there are existing conditions in which an equivalent soil moisture value can be used in predictive models operating at the daily scale. Solving this problem is interesting as a failsafe feature in capabilities of the more complex system, as well as an improvement in understanding better the soil processes themselves. In the current work, we design an experimental soil column which allows one to relate water dynamics to gas emissions in a closed-controlled environment.