Integration and testing of the Hot-Spot submodel with the DNDCv.Can model on the results of a manure-soil laboratory experiment

Biogeochemical models are useful tools for modeling nitrous oxide (N₂O) emissions from agricultural mineral soils. However, most biogeochemical models assume that conditions favoring N₂O producing reactions, nitrification and denitrification, are spatially homogeneous distributed in soil. Recent studies have shown, that conditions favoring N₂O producing, like the availability of easy degradable organic carbon, nitrate and ammonium and the establishment of anaerobic conditions are often concentrated in hot spots around particular organic matter originating from crop residues and organic amendments. In contrast to common biogeochemical models, spatially explicit models are required to better describe dynamics of N₂O emissions.

To address the role of spatial heterogeneity of conditions responsible for nitrification and denitrification, we introduce a model approach combining biogeochemical process descriptions at hot spots and the bulk soil. The „hot spot” part of the model includes the description of diffusive transport of solutes and gases in a spherical object combined with process descriptions like mineralization, nitrification, nitrifier denitrification and denitrification. Several instances of the hot spot module then interact with the model approach describing processes in the bulk soil.

In this study, a laboratory experiment will be modeled in order to simulate the application of a single type of manure on the surface and the injection of manure into the center of a column in sandy and loess soils with water contents set at 40% and 60% WFPS.

The submodel will be integrated into the DNDCv.Can model, which provides the boundary conditions and input data required for the submodel and also participates in determining the O₂ concentration by explicitly calculating the diffusion from the surface to the soil layer where the hot spot is located.

Our hypothesis is that the DNDCv.Can model with the hot spot submodule will be able to describe the daily dynamics of the nitrification and denitrification processes generated by the hot spot induced in the experiment more accurately, which would greatly help the further development of the model for the application of this approach in real agricultural practice.