Nitrogen application rate and nitrous oxide flux from a pastoral soil

Figures & data

Figure 1 Time courses of the mean pH in: A, the upper (0–5 cm depth) and B, lower (5–10 cm depth) layers of soil samples including 1 day before nitrogen (N) application. The symbols denote different N application rates (kg N ha⁻¹, • control (zero), ○ N25, ▴ N50, Δ N100, ▪ N250, □ N500, ♦ N1000, ⋄ N1500).

Figure 2 Time courses of the mean ammonium concentration (± SE, n = 3) in: A, the upper (0–5 cm depth) and B, lower (5–10 cm depth) layers of soil samples including 1 day before nitrogen (N) application. The symbols denote different N application rates (kg N ha⁻¹, • control (zero), ○ N25, ▴ N50, Δ N100, ▪ N250, □ N500, ♦ N1000, ⋄ N1500).

Figure 3 Time courses of the mean nitrate concentration (± SE, n = 3) in: A, the upper (0–5 cm depth) and B, lower (5–10 cm depth) layers of soil samples including 1 day before nitrogen (N) application. The symbols denote different N application rates (kg N ha⁻¹, • control (zero), ○ N25, ▴ N50, Δ N100, ▪ N250, □ N500, ♦ N1000, ⋄ N1500).

Figure 4 Time courses of the mean nitrous oxide (N₂O) flux (± SE, n = 3) including 1 day before nitrogen (N) application. The symbols denote different N application rates (kg N ha⁻¹, • control (zero), ○ N25, ▴ N50, Δ N100, ▪ N250, □ N500, ♦ N1000, ⋄ N1500).

Figure 5 The relationship between nitrogen (N) application rate (Nrate, kg N ha⁻¹) and the replicate nitrous oxide (N₂O) fluxes accumulated over 67 days (kg N ha⁻¹). Linear regression yielded N₂O flux = (0.0122 ± 0.0006) * Nrate + 0.8352 ± 0.0626, a statistically significant relationship (P < 0.05) accounting for 92% of the variability.