Modelling uncertainty for nitrate leaching and nitrous oxide emissions based on a Swedish field experiment with organic crop rotation

J. Nylinder^1*, M. Stenberg^2,3,3, P. E. Jansson⁴, A. K. Klemedtsson⁵ and L. Klemedtsson¹

Abstract
High uncertainties are common in detailed quantification of the N budget of agricultural cropping systems. The process-based CoupModel, integrated with the parameter calibration method known as Generalized likelihood uncertainty estimation (GLUE), was used here to define parameter values and estimate an N budget based on experimental data from an organic farming experiment in south-west Sweden.

Data on nitrate (NO₃⁻) leaching and nitrous oxide (N₂O) emissions were used as a basis for quantifying N budget pools. A complete N budget with uncertainties associated with the different components of the N cycle compartments for two different fields (B2 and B4) is presented.

Simulated N₂O emissions contributed 1–2% of total N output, which corresponded to 7% and 8.7% of total N leaching for B2 and B4, respectively. Measured N₂O emissions contributed 3.5% and 10.3% of total N leaching from B2 and B4, respectively. Simulated N inputs (deposition, plant N fixation and fertilisation) and outputs (emissions, leaching and harvest) showed a relatively small range of uncertainty, while the differences in N storage in the soil exhibited a larger range of uncertainty. One-fifth of the GLUE-calibrated parameters had a significant impact on simulated NO₃⁻ leaching and/or N₂O emissions data. Emissions of N₂O were strongly associated with the nitrification process. The high degree of equifinality indicated that a simpler model could be calibrated to the same field data.


Source
Agriculture, Ecosystems and Environment (2011) 141: 167-183
DOI: 10.1016/j.agee.2011.02.027


Author Locations and Affiliations
(1) Department of Plant and Environmental Sciences, University of Gothenburg, PO Box 461, SE-405 30 Göteborg, Sweden
(2) Rural Economy and Agricultural Society of Skaraborg, PO Box 124, SE-532 22 Skara, Sweden
(3) Department of Soil and Environment, Swedish Agriculture University, PO Box 234, SE-532 23 Skara, Sweden
(4) Department of Land and Water Resources Engineering, Royal Institute of Technology, SE-100 44 Stockholm, Sweden
(5) Department of Earth Sciences, University of Gothenburg, PO Box 461, SE-405 30 Göteborg, Sweden
* Corresponding author, E-mail Josefine.Nylinder@dpes.gu.se


Posted May 2011