Measuring N2O Emissions from Multiple Sources Using a Backward Lagrangian Stochastic Model

<p>Nitrous oxide (N<sub>2</sub>O) emissions from agricultural soil are substantially influenced by nitrogen (N) and field management practices. While routinely soil chambers have been used to measure emissions from small plots, measuring field-scale emissions with micrometeorological methods has been limited. This study implemented a backward Lagrangian stochastic (bLS) technique to simultaneously and near-continuously measure N<sub>2</sub>O emissions from four adjacent fields of approximately 1-ha each. A scanning open-path Fourier transform infrared spectrometer (OP-FTIR), edge-of-field gas sampling and measurement, locally measured turbulence, and bLS emissions modeling were integrated to measure N<sub>2</sub>O emissions from four adjacent fields of maize production using different management in 2015. The maize N management treatments consisted of 220 kg NH<sub>3</sub>-N ha<sup>-1</sup> applied either as one application in the fall after harvest or spring before planting or split between fall after harvest and spring before planting. The field preparation treatments evaluated were no-till (NT) and chisel plow (ChP). This study showed that the management of the full-N rate applied in fall led to higher N<sub>2</sub>O emissions than the split-N rates applied in the fall and spring. Based on the same N application (i.e., split-N rates applied in the fall and spring), the ChP practice tended to increase N<sub>2</sub>O emissions compared with NT. The method had a minimum detection limit (MDL) of ±1.2 µgm<sup>-2</sup> s<sup>-1</sup> (3σ). The averaged emission rates of the four treatments over 41 days after the spring fertilizer application ranged from 0.8 to 3.9 µg m<sup>-2</sup> s<sup>-1</sup>. Advection of N<sub>2</sub>O from adjacent fields influenced the estimated emissions; uncertainty (1σ) in emissions was 0.5±0.3 µg m<sup>-2</sup> s<sup>-1</sup> if the field of interest received a clean measured upwind background air but increased to 0.6±0.4 µg m<sup>-2</sup> s<sup>-1</sup> if there was one predominant upwind source advecting into the field of interest and then to 1.1±0.5 µg m<sup>-2</sup> s<sup>-1</sup> if all fields were advecting N<sub>2</sub>O over the field of interest.</p>

<p>These data refer to figures 1b, 3, 4, 5, 6, 7a, and 7b of Lin, C.-H., Grant, R. H., and Johnston, C. T. (2020) Measuring N2O Emissions from Multiple Sources Using a Backward Lagrangian Stochastic Model. Atmosphere.</p>