Figure 2. Pulse NO_x emission responses to dissolved ammonium nitrate fertilization.

(a) Soil NO_x fluxes observed during a N-fertilization experiment in 2012 where collars received 20 kg ammonium nitrate-N ha⁻¹ in dissolved form during an irrigation (white circles; n=10) and control collars received irrigation only (black circles; n=10; s.d. bars shown). The irrigation and fertilization event is indicated by an arrow (DOY 262). N treatment significantly increased NO_x emissions with peak emissions observed 7 days post fertilization. (b) Control collar NO_x fluxes were also evaluated in a separate analysis to investigate the influence of irrigation alone on NO_x flux. Control NO_x fluxes were significantly affected by time during the experiment in response to irrigation, where fluxes observed during the third measurement (7 days post treatment) were significantly different from all other measurements except for the fourth measurement (14 days post treatment). Significant differences between time points are indicated by letters (p, q) at P<0.05, as determined using pairwise comparisons with Bonferroni adjustment.