Ferland D, Wagner-Riddle C, Brown S E, Bourgault M, Helgason W, Farrell R E, Congreves K A
Department of Plant Sciences, University of Saskatchewan, Saskatchewan, Canada.
School of Environmental Science, University of Guelph, Ontario, Canada.
Sci Total Environ. 2024 Dec 15;956:177211. doi: 10.1016/j.scitotenv.2024.177211. Epub 2024 Nov 4.
Arable croplands are a significant source of nitrous oxide (NO) emissions, largely due to nitrogen (N) fertilizer applications to support crop production. Nevertheless, there is limited research on the NO dynamics from canola-wheat rotations in the semi-arid northern Prairies, an important agricultural region. Here, we present micrometeorological NO fluxes measured from January 2021 to April 2024 in Saskatchewan, Canada, to evaluate the impact of N fertilizer management on the year-round NO emissions from a canola-wheat rotation. A combination of two 4R (Right Source, Right Rate, Right Time, Right Place) N management practices - a reduced N rate and an enhanced efficiency N fertilizer source - was compared to common fertilizer management practices for the region. Two periods at high risk for NO flux events were identified, after N fertilizer applications and the following spring thaw, with the magnitude of emissions varying over the multi-year period. As for cumulative emissions, the growing season (GS) NO emissions were 50 % of annual emissions, presenting an opportunity to mitigate NO emissions through improved N fertilizer management. Indeed, the improved 4R N management reduced NO emissions by 57 % over the entire study period without impacting yields. The reduction in GS NO emissions resulted from the 4R N management lowering mean NO flux at times of high WFPS (>50 %). The non-growing season (NGS) NO accounted for 11-67 % of annual emissions. Fall soil nitrate levels were a strong explanatory variable of NGS emissions (r = 0.69, r = 0.39), but the rate of change and magnitude of NGS emissions depended on thawing conditions - lower for drier thaws, higher for wetter thaws. Ultimately, better N fertilizer management reduces cumulative NO emissions from cropping systems when practiced for several years.
耕地是一氧化二氮（N₂O）排放的重要来源，这主要归因于为支持作物生产而施用的氮肥。然而，在半干旱的北部大草原这一重要农业区域，关于油菜 - 小麦轮作体系中N₂O动态的研究有限。在此，我们展示了2021年1月至2024年4月在加拿大萨斯喀彻温省测量的微气象N₂O通量，以评估氮肥管理对油菜 - 小麦轮作体系全年N₂O排放的影响。将两种4R（正确的来源、正确的用量、正确的时间、正确的地点）氮肥管理措施（降低氮肥用量和使用增效氮肥源）相结合，并与该地区常见的肥料管理措施进行比较。确定了两个N₂O通量事件的高风险时期，分别是在施用氮肥后以及次年春季解冻后，多年来排放规模有所不同。至于累积排放量，生长季（GS）的N₂O排放量占年排放量的50%，这为通过改进氮肥管理来减少N₂O排放提供了机会。事实上，改进后的4R氮肥管理在不影响产量的情况下，在整个研究期间将N₂O排放量减少了57%。生长季N₂O排放量的减少是由于4R氮肥管理降低了高土壤水分含量（WFPS）（>50%）时的平均N₂O通量。非生长季（NGS）的N₂O排放量占年排放量的11 - 67%。秋季土壤硝酸盐水平是解释非生长季排放的一个重要变量（r = 0.69，r = 0.39），但非生长季排放的变化速率和规模取决于解冻条件——较干燥解冻时排放较低，较湿润解冻时排放较高。最终，多年实施更好的氮肥管理可减少种植系统的累积N₂O排放。
