Treatment mean separations for grain yield (GY), and yield-scaled N2O–N

Table 4. Treatment mean separations for grain yield (GY), and yield-scaled N2O–N. Means presented in this table are obtained from the back-transformed data for yield-scaled means. Pre-emergence (Pre), and side-dress (Side). Different letters indicate statistically significant differences within columns (Scheffe-5%). p-values for each variable are included at the bottom of the table. (Notes: ,, significant at 0.05, 0.01 and 0.001 probability levels, respectively.) Abstract Nitrification inhibitors have the potential to reduce N2O emissions from maize fields, but optimal results may depend on deployment of integrated N fertilizer management systems that increase yields achieved per unit of N2O lost. A new micro-encapsulated formulation of nitrapyrin for liquid N fertilizers became available to US farmers in 2010. Our research objectives were to (i) assess the impacts of urea–ammonium nitrate (UAN) management practices (timing, rate and nitrification inhibitor) and environmental variables on growing-season N2O fluxes and (ii) identify UAN treatment combinations that both reduce N2O emissions and optimize maize productivity. Field experiments near West Lafayette, Indiana in 2010 and 2011 examined three N rates (0, 90 and 180 kg N ha−1), two timings (pre-emergence and side-dress) and presence or absence of nitrapyrin. Mean cumulative N2O–N emissions (Q10 corrected) were 0.81, 1.83 and 3.52 kg N2O–N ha−1 for the rates of 0, 90 and 180 kg N ha−1, respectively; 1.80 and 2.31 kg N2O–N ha−1 for pre-emergence and side-dress timings, respectively; and 1.77 versus 2.34 kg N2O–N ha−1 for with and without nitrapyrin, respectively. Yield-scaled N2O–N emissions increased with N rates as anticipated (averaging 167, 204 and 328 g N2O–N Mg grain−1 for the 0, 90 and 180 kg N ha−1 rates), but were 22% greater with the side-dress timing than the pre-emergence timing (when averaged across N rates and inhibitor treatments) because of environmental conditions following later applications. Overall yield-scaled N2O–N emissions were 22% lower with nitrapyrin than without the inhibitor, but these did not interact with N rate or timing.

表4 籽粒产量（grain yield, GY）及产量标度化N₂O-N的处理均值多重比较结果。本表所列均值均由产量标度化均值的反变换数据计算得到。播前施肥（Pre）与侧施追肥（Side）。列内不同字母代表组间具有统计学显著差异（Scheffe检验，显著性水平5%）。各变量的p值列于本表底部。注：分别表示在0.05、0.01和0.001概率水平下显著。

摘要：硝化抑制剂可降低玉米田N₂O排放，但最优减排效果可能依赖于一体化氮肥管理体系的应用，该体系可提升单位N₂O损失对应的籽粒产量。2010年，一款适用于液态氮肥的新型微胶囊剂型硝化吡啉（nitrapyrin）面向美国农户上市。本研究目标为：（1）评估尿素硝酸铵溶液（urea–ammonium nitrate, UAN）管理措施（施肥时期、施氮量及硝化抑制剂）与环境变量对生育期N₂O通量的影响；（2）筛选出既能降低N₂O排放又能优化玉米生产性能的UAN处理组合。2010年与2011年，在印第安纳州西拉法叶市周边开展田间试验，设置3个施氮水平（0、90和180 kg N·ha⁻¹）、2个施肥时期（播前与侧施追肥）以及是否添加硝化吡啉共4个处理维度。经Q10校正的累积N₂O-N排放量均值，在施氮量为0、90和180 kg N·ha⁻¹时分别为0.81、1.83和3.52 kg N₂O-N·ha⁻¹；播前施肥与侧施追肥时期分别为1.80和2.31 kg N₂O-N·ha⁻¹；添加与不添加硝化吡啉时分别为1.77和2.34 kg N₂O-N·ha⁻¹。产量标度化N₂O-N排放量随施氮量增加而升高，与预期一致（施氮量为0、90和180 kg N·ha⁻¹时，均值分别为167、204和328 g N₂O-N·Mg⁻¹籽粒）；但侧施追肥时期的排放量较播前施肥高22%（综合所有施氮水平与抑制剂处理的均值），这是由于后期施肥后的环境条件差异导致的。整体而言，添加硝化吡啉的产量标度化N₂O-N排放量较不添加时低22%，但该效果与施氮量或施肥时期无交互作用。