Speaker
Description
Agriculture stands as a fundamental pillar of human sustenance, meeting the growing global demand for food, feed and fiber. Within this context, the use of fertilizers, especially nitrogen (N) based, has been pivotal in enhancing crop productivity. However, excess usage of nitrogen not only leads to economic losses but also has negative environmental consequences, such as the emission of greenhouse gases. Among these gases, the nitrous oxide (N2O) stands out as a direct derivate of the use of N fertilizers. N2O is a long-lasting anthropogenic greenhouse gas (IPCC 2019) and has a global warming potential (GWP) of 298 times higher than carbon dioxide (CO2). Emissions are highly variable in space and time and depend on biological (microbial activity), physical (rainfall) or environmental (frost-thaw cycles) factors as well as the availability of N (Ito et al. 2018). Since the dynamics of N is a central piece in crop models, these can be an appropriate tool to integrate multiple environmental factors and management practices to understand N2O fluxes in agricultural systems. In this study, the model HERMES was tested in its ability to simulate N2O production in an experiment with varying fertilizer types.
The experiment was planned as an on-farm strip design spanning three consecutive crop rotations (maize, wheat, barley) in NE Germany (Uckermark Region, “53°18'54.2"N, 13°40'15.2"E”). The mineral N fertilizer used was ammonium sulfate urea (AS-HS; 33%N 12%S) and tested in combination with a urease inhibitor (UI) and a nitrification inhibitor (NI). The on-farm field trial was divided into four equal stripes, with the following treatments: 1) Control (non-fertilized); 2) mineral N fertilizer (AS-HS); 3) fertilizer with urease inhibitor (AS-HS+UI); and 4) fertilizer with urease and nitrification inhibitor (AS-HS+UI+NI), respectively. N2O (and CH4) emissions were measured using NFT-NSS opaque chambers, evacuated glass vials for sampling and subsequent gas chromatography analyses (Shimadzu GC-14B with ECD and FID detectors). Experimental conditions were reproduced in the model HERMES, which combines a series of basic modules (soil, crop, field management, N cycle), to simulate yield, biomass and, among other outputs, N2O production (Kersebaum 2019). Model results were compared with field measurements.
The model was able to predict most of the N2O emission events (peaks) and showed a high sensitivity to the effect of rain events on N2O production. Fertilization events played a relatively lower role in the production of N2O, indicating that the model might need adjustments in this respect. Crop and soil parameter calibration is currently being carried out to adjust the simulations to fit additional measurements. Preliminary results of this study also showed the need to adjust the fertilizer parameterization to accurately discriminate between fertilizer types.
References
- IPCC (2019): Climate change and land. An IPCC special report on
climate change, desertification, land degradation, sustainable land
management, food security, and greenhouse gas fluxes in terrestrial
ecosystems : summary for policymakers. [Geneva]: Intergovernmental
Panel on Climate Change. - Ito, Akihiko; Nishina, Kazuya; Ishijima,
Kentaro; Hashimoto, Shoji; Inatomi, Motoko (2018): Emissions of
nitrous oxide (N2O) from soil surfaces and their historical changes
in East Asia: a model-based assessment. In Prog Earth Planet Sci 5
(1). DOI: 10.1186/s40645-018-0215-4. - Kersebaum, K.C., Wallor, E.,
Lorenz, K., Beaudoin, N., Constantin, J., & Wendroth, O. (2019).
Modeling cropping systems with HERMES–Model capability, deficits and
data requirements. Bridging Among Disciplines by Synthesizing Soil
and Plant Processes, 103-126.n
https://doi.org/10.2134/advagricsystmodel8.2017.0005
| Keywords | N2O fluxes, crop model, soil, fertilizer type, greenhouse gas emissions |
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