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DASIM - Denitrification in Agricultural Soils: Integrated control and Modelling at various scales

Funding Agency: DFG //  Duration: 2016 - 2023 // PI: Christoph Müller


Denitrification is the process of nitrate reduction which allows microbes to breathe under aerobic conditions, is a key process of reactive nitrogen from the soil as inert N2 returns to the atmosphere. The individual steps (NO3- -> NO2- -> NO -> N2O -> N2) are enzymatically controlled by a large number of pro- and eukaryotes. Active denitrifiers communities in soil exhibit distinct regulatory phenotypes (DRP), with characteristic control of individual reaction steps and end products. It is unclear whether DRPs are taxonomically fixed in denitrifiers and how much environmental conditions can change them. Although research on DRPs has been going on for over 100 years, denitrification rates and the emission of gaseous products still cannot be satisfactorily explained and predicted. While the influence of individual environmental conditions is already well understood, the complexity of the overall process with its complicated cellular regulation as a reaction to very variable factors in the soil matrix has not yet been clarified. Key parameters are the oxygen partial pressure in the soil, the content of organic material and its quality, the pH value and the composition of the microbial community, which in turn is determined by soil structure, soil chemistry and soil-plant interaction. In this project we aim to make quantitative predictions of denitrification rates as a function of soil microstructure, organic mass quality, DRPs and atmospheric boundary layer condition. We rely on the latest experimental and analytical methods (X-ray µCT, 15N tracing, NanoSIMS, microsensors, advanced flux detection, NMR spectroscopy, molecular methods including "next generation sequencing of functional gene transcripts") to achieve a very accurate spatial and temporal resolution of the process steps. Improved numerical methods and computer capacities will allow to integrate the results of the individual groups and to develop new denitrification models ranging from the microscale (phase 1) to the field scale (phase 2).