Modelling the Impact of Crop Residue Management, Organic Fertilization and associated Application Techniques on N2O and N2 Emissions from Agricultural Soils (MOFANE 2)

• Applicants: Dr.-Ing. Rene Dechow; Dr. Maik Lucas; Privatdozent Dr. Reinhard Well
• Subject Area: Soil Sciences
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 546285662

Fertilizing arable soils with liquid manures and incorporation of crop residues affects gaseous N losses to the atmosphere including NO, N2O and N2 as well as nitrate leaching. Their extent depends on the complex interaction between manure and crop residue management techniques and properties of these substrates and soil. The first phase of MOFANE addressed the general question, how liquid manure fertilization and its application mode impact N2O and N2 fluxes from agricultural soils, how their optimization could mitigate emission while maintaining crop yields and how models would have to be improved to find answers. We addressed this by targeted experiments to quantify N2, N2O and NO fluxes as well as gross rates of mineralization and nitrification of soil-manure systems under controlled conditions and using results to evaluate and improve models. Here, we apply for a follow-up of MOFANE with the goals to include crop residue effects on denitrification dynamics to our models and to quantify pore structure and distribution of manure and crop residues to supply improved input data for the model. Building on the achievements of the first phase we now quantify hotspots created through organic fertilizer application directly using a combination of X-ray CT and O2-microsensors in incubation experiments with structured soil. Further, while in the first phase the focus was on manure only, we will also investigate the incorporation of plant residues. Our work program includes the following experimental and modeling tasks. • Experimental exploration of denitrification in structured soil under realistic conditions with 1) different organic substrates, namely manure and plant residues and 2) different application, incorporated by ploughing (conventional tillage, CT) and using a cultivator (reduced tillage, RT) • Reducing the structural complexity of natural undisturbed soil to a limited set of meaningful quantities derived by X-ray CT, which can be translated to model parameters describing the 1) hotspot, the bulk soil and their boundary layer and 2) the distribution of the hotspots. • Explorative model development to describe hot spot effects of manure and crop residue incorporation by conventional and reduced tillage on denitrification, including further improvement and development of the DyMaN sub-module that was originally designed to model spatial manure effects to cover also crop residue hot spot effects. • Implementation of model approaches describing spatial effects on C and N cycling into the biogeochemical model DNDCv.CAN. Model validation of the integrated model along existing data sets

• DFG Programme: Research Grants