Aims

Perennial forages in rotation with annual crops can improve agricultural resilience by increasing soil organic carbon. However, how nitrogen (N) sources interact with rotation diversity to influence soil nitrous oxide (N₂O) emissions is not well understood.

Methods

During three snow-free seasons, N₂O emissions, crop yields, and ancillary variables were measured at three experimental sites with contrasting soil textures (silty clay and sandy loam) in eastern Canada. Using a split-plot design, we compared a corn (Zea mays L.)-soybean (Glycine max [L.] Merr.)-corn rotation and a mixed perennial grass sward receiving N via: i) mineral fertilizer (MIN), ii) liquid dairy manure (LDM), and iii) inclusion of alfalfa (Medicago sativa L.) to the perennial forages with no additional N (LEG).

Results

When summed across sites over all three years, cumulative N₂O emissions were greater for LDM than MIN in annual crops (8.75 ± 1.63 and 5.15 ± 0.96 kg N₂O-N ha^–1, respectively), but not in perennial grasses (2.95 ± 0.55 and 3.76 ± 0.70 kg N₂O-N ha^–1, respectively). When comparing N sources within each crop type over the three years, MIN generated greater yields than LDM in annual and perennial crops, but lower yield-scaled N₂O emissions than LDM in annual crops only. During forages post-seeding years, area- and yield-scaled N₂O emissions induced by LDM and LEG were lower than MIN.

Conclusion

Our results suggest that for a cool humid climate using LDM or LEG in perennial forages and MIN on annual crops can reduce overall N₂O emissions, while generating similar or lower yield-scaled emissions.

中文翻译：

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凉爽潮湿气候下作物类型和氮源对 N2O 排放的交互影响

 目标

多年生牧草与一年生作物轮作可以通过增加土壤有机碳来提高农业恢复力。然而，氮 （N） 源如何与轮作多样性相互作用以影响土壤一氧化二氮 （N₂O） 排放尚不清楚。

 方法

在三个无雪季节中，在加拿大东部土壤质地截然不同的三个实验点（粉质粘土和沙壤土）测量了 N₂O 排放、作物产量和辅助变量。使用裂区设计，我们比较了玉米 （Zea mays L.）-大豆 （Glycine max [L.] Merr.）-玉米轮作和混合多年生草草地接收氮，方法为：i）矿物肥料（MIN），ii）液体奶牛粪（LDM），以及iii）在多年生牧草中加入紫花苜蓿（Medicago sativa L.），无需额外的氮（LEG）。

 结果

在所有三年中，当各地点相加时，在一年生作物中，LDM 的累积 N₂O 排放量大于 MIN（分别为 8.75 ± 1.63 和 5.15 ± 0.96_{kg N 2} ^{O-N ha–1}），但在多年生草类中则不然（分别为 2.95 ± 0.55 和 3.76 ± 0.70_{kg N 2}O-N ha^–1）。在比较三年中每种作物类型中的氮源时，MIN 在一年生和多年生作物中产生的产量高于 LDM，但在一年生作物中，产量比例的 N₂O 排放量低于 LDM。在牧草播种后几年，LDM 和 LEG 诱导的面积和产量比例的 N₂O 排放低于 MIN。

 结论

我们的结果表明，在凉爽潮湿的气候下，在多年生牧草中使用 LDM 或 LEG，在一年生作物上使用 MIN 可以减少总体 N₂O 排放，同时产生相似或较低的产量排放。