P3 Relevance of functional soil organic matter fractions for kinetics and spatiotemporal patterns of denitrification [funded by DFG]

Project staff:

Prof. Dr. Jürgen Böttcher
Prof. Dr. Robert Mikutta
M.Sc. Ronny Surey


Despite soil organic matter (OM) is known as an important ecosystem property which fuels denitrification, the understanding of the role of OM quality and its spatial and temporal availability is only at the beginning. Therefore, the goal of our application is to investigate the relevance of functional OM fractions (DOM, POM, MOM) as stimulants for denitrification in agricultural soils. In phase one of the RU, we attempt to clarify (i) the effect of OM source, composition, and content, (ii) the consequences of the spatial distribution of OM fractions in soil, and (iii) the interplay with abiotic factors (NO3- and O2 availability) on soil denitrification, including kinetics and gas products. Although, temperature is an important abiotic factor for denitrification activity in soil, we intend to investigate temperature effects on availability and reactivity of OM fractions in detail in phase two of the RU.
Our experimental approach in phase one is based on a bottom-up concept where we will first address independently the role of individual OM components in controlled incubation experiments under the influence of abiotic factors (Task 1, DOM; Task 2, POM; Task 3, MOM). It then continues with more complex systems (Task 4, central mesocosm experiments) focussing on the spatial distribution of OM fractions in soil aggregates and their impact on denitrification. The results obtained in Task 1-4 during the first phase of the RU set the scientific basis for developing an "OM quality index" which will describe the impact of OM fractions and their quality in soil denitrification models.