INFlux (2022 - 2025)

Improved process understanding and quantification of Nitrous oxide FLUXes in a German crop rotation

Nitrous oxide (N₂O) is one of the most powerful greenhouse gases (GHG) and agricultural soils are one of its larger sources. Quantification of N₂O emissions is challenging because of the high temporal and spatial variability of the fluxes and the underlying processes remain poorly understood. Quantifying and understanding N₂O fluxes is the first step to develop mitigation strategies for agricultural systems. The objectives of the research project INFLUX are to quantify N₂O fluxes and to improve the mechanistic understanding of the fluxes in a German crop rotation (sugar beet, barley, wheat). The most common method to quantify N₂O fluxes are manual chambers, which are easy to manipulate and can reveal information about the spatial distribution of N₂O emissions in the field. However, they fail at capturing the temporal variability of the fluxes.

The Eddy Covariance (EC) method provides non-intrusive flux data at the ecosystem scale with high temporal resolution and therefore offers the opportunity to better understand the short-term variability of N2O fluxes.

Eine Wissenschaftlerin und ein Wissenschaftler arbeiten hinter einer Glasfassade und mischen Chemikalien mit Großgeräten.

Scheme of Work Packages and relationship between them © INFlux

In the INFLUX project, we will (i) compare high-resolution N₂O data measured with the EC technique and the chamber method at the Experimental Farm Reinshof for two years. Additionally, the full GHG balance will be assessed, considering also carbon dioxide and methane fluxes, i.e. the global warming potential and the greenhouse gas intensity, which relates GHG emissions with crop yields.

Additionally, we will (ii) relate the fluxes to environmental conditions, management practices and crop development to improve the understanding of the effects of agricultural management on emissions. N₂O emissions strongly depend on soil nitrogen and carbon availability, oxygen concentration/ soil moisture, soil temperature and pH. Therefore, weather events like rainfall or freeze-thaw cycles, as well as management practices like fertilization or tillage, can lead to enhanced N₂O production. Continuously monitoring climatic conditions, soil parameters, management practices and crop development will provide information on which are the most relevant drivers for N₂O fluxes in this cropping system.

Finally, to gain a better understanding of the mechanisms responsible for N₂O production, (iii) the high-resolution measurements of N₂O fluxes and its drivers will be combined with isotopic and metagenomic analysis. Stable isotope analysis provides new opportunities for source partitioning of soil-emitted N₂O. We will study the ¹⁵N site preference and use the isotopocule mapping approach to identify production and consumption processes. It will additionally be possible to distinguish between N₂O source processes in the soil. Those analyses will be completed by molecular methods. Metagenomic analysis of gene abundances in the soil will provide information on the microbial communities and the potential activities involved in N₂O production and consumption. As these soil microbial communities are likely to be affected by water/nutrient availability, examining their abundances alongside soil characteristics and GHG fluxes could improve identification of N₂O drivers associated with crop management.

The unique dataset that will be generated in INFLUX will allow to understand which are the most relevant mechanisms responsible for N₂O emissions in an agricultural soil.