Fertilizer Source Influenced Nitrous Oxide Emissions from a Clay Soil under Corn
2011
Gagnon, Bernard | Ziadi, Noura | Rochette, Philippe | Chantigny, Martin H. | Angers, Denis A.
Synthetic N fertilizers are a major source of N₂O emissions from soil. A field experiment was conducted during three growing seasons (2004–2006) on a clay soil (fine, mixed, frigid Typic Humaquept) under corn (Zea mays L.) to evaluate the impact of N fertilizer source and application rate on N₂O emissions. Treatments consisted of three sources of N fertilizer (urea–NH₄NO₃ 32% [UAN], Ca–NH₄NO₃ [CAN], and aqua NH₃ [AA]) at four different rates (0, 100, 150, and 200 kg N ha⁻¹). Fertilizers were banded 5 cm below the soil surface between corn rows at the six-leaf stage and N₂O emissions were measured weekly. For all 3 yr of this study, cumulative N₂O emission decreased in the order UAN ≥ CAN ≥ AA. Averaged across years, fertilizer-induced post-sidedress emissions were greater than the Intergovernmental Panel on Climate Change default factor (0.01 kg N₂O-N kg⁻¹ N), with values of 0.038, 0.033, and 0.027 kg N₂O-N kg⁻¹ N for UAN, CAN, and AA, respectively. The N₂O emissions increased linearly with N rate, even at rates exceeding the optimum level for grain yield. Peaks of N₂O flux occurred on the days following fertilizer application and in early fall when the soil was re-wetted. Emissions of N₂O were higher at water-filled pore space >0.57 m³ m⁻³ and were also related to soil inorganic N and water-extractable organic C contents. Our results confirm that N fertilizer source and application rate can impact N₂O emissions but these effects are modulated by soil environmental conditions.
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