N2O emissions from agricultural lands: a synthesis of simulation approaches

Abstract

Nitrous oxide (N 2 O) is primarily produced by the microbially-mediated nitrification and denitrification processes in soils. It is influenced by a suite of climate (i.e. temperature and rainfall) and soil (physical and chemical) variables, interacting soil and plant nitrogen (N) transformations (either competing or supplying substrates) as well as land management practices. It is not surprising that N 2 O emissions are highly variable both spatially and temporally. Computer simulation models, which can integrate all of these variables, are required for the complex task of providing quantitative determinations of N 2 O emissions. Numerous simulation models have been developed to predict N 2 O production. Each model has its own philosophy in constructing simulation components as well as performance strengths. The models range from those that attempt to comprehensively simulate all soil processes to more empirical approaches requiring minimal input data. These N 2 O simulation models can be classified into three categories: laboratory, field and regional/global levels. Process-based field-scale N 2 O simulation models, which simulate whole agroecosystems and can be used to develop N 2 O mitigation measures, are the most widely used. The current challenge is how to scale up the relatively more robust field-scale model to catchment, regional and national scales. This paper reviews the development history, main construction components, strengths, limitations and applications of N 2 O emissions models, which have been published in the literature. The three scale levels are considered and the current knowledge gaps and challenges in modelling N 2 O emissions from soils are discussed.

Mitigating N<sub>2</sub>O emissions from soil: from patching leaks to transformative action

“…Tremendous progress has been made during the last decennia with respect to the scientific understanding of N 2 O emissions from soils: various pathways and mechanisms have been elucidated (Butterbach-Bahl et al, 2013); molecular and isotopic tools to assess mechanisms have been advanced (Baggs, 2008(Baggs, , 2011Decock and Six, 2013); we have a general idea of temporal and spatial patterns of N 2 O emissions (Groffman et al, 2009); micrometeorological methods are available to monitor spatially integrated N 2 O emissions at high temporal resolution (Eugster and Merbold, 2015); various data sources have been synthesized in qualitative and quantitative reviews (Bouwman, 1996;Decock, 2014); and biogeochemical models have been developed and improved to predict N 2 O emissions under various scenarios (Chen et al, 2008). These efforts have paved the way to identify the major causes of soil-derived N 2 O and to isolate the strategies that have the greatest potential for reducing global N 2 O emissions (e.g.…”

“…Models are in essence a mathematical representation of our understanding of functional relationships between the key drivers, their interactions and the ecosystem responses under different agricultural managements (Chen et al, 2008). Hence, model predictions can only be as accurate as our current understanding of the underlying mechanisms.…”

Spatial and temporal variability of nitrous oxide emissions in a mixed farming landscape of Denmark

“…Within the Bjerringbro landscape, we found large N 2 O emissions from an arable field after the application and incorporation of farmyard manure and attributed the N 2 O losses to lumps of manure acting as hotspots within the field soil. These emissions may be difficult to predict using even the best available models (Chen et al, 2008;Farquharson and Baldock, 2008).…”

A Novel Method Combining FTIR-ATR Spectroscopy and Stable Isotopes to Investigate the Kinetics of Nitrogen Transformations in Soils

“…N ew and innovative methods for investigating N transformations in soils are crucial for improving the knowledge of the complex N-cycle in agricultural soils and for quantification of formation rates of N-species (e.g., NO 3 − , NH 4 + /NH 3 , N 2 O) which pollute the environment (Chen et al, 2008;Imran et al, 2009;Ghiglieri et al, 2009;Skiba et al, 2000). Common methods for investigating N transformations include soil incubations with ammonium (NH 4 + ) and/or nitrate (NO 3 − ).…”