Multispecies pastures containing grasses, N-fixing legumes and forage herbs can maintain high herbage dry matter (DM) yield, while reducing the need for fertiliser N inputs thus potentially reducing harmful N losses such as nitrous oxide (N₂O) emission and nitrate (NO₃⁻) leaching to the wider environment. However, our understanding of these processes in grassland swards of contrasting composition is still very limited. A lysimeter experiment was carried out over 12 months to test the hypotheses that (1) cumulative and (2) seasonal N₂O emission and N leaching would be highest from the Perennial Ryegrass only (PRG, 250 kg N ha^-1 yr^-1) treatment compared to three other treatments; Perennial Ryegrass and Low White Clover (PRG+LWC, 90 kg N ha^-1 yr^-1), Perennial Ryegrass and High White Clover (PRG+HWC, 0 kg N ha^-1 yr^-1) and Perennial Ryegrass, White Clover and Ribwort Plantain (PRG+WC+P, 45 kg N ha^-1 yr^-1) and (3) that the soil N cycling pathways (nitrification/denitrification) linked to these N losses would be different between treatments. Cumulative N₂O emissions (2.74–3.25 kg N₂O-N ha^-1), leached N (10.91–13.70 kg N ha^-1), DM yields (5083–5493 kg DM ha^-1 yr^-1) and N uptake (122–169 kg N ha^-1 yr^-1) were not significantly different between treatments. Nitrogen yield scaled N₂O emissions were significantly lower from all other treatments compared to the high fertiliser N input PRG monoculture. A significant interaction between treatment and season showed that in Spring, N₂O emission was significantly higher from PRG (1.39 kg N₂O-N ha^-1) and PRG+LWC (1.19 kg N₂O-N ha^-1) than PRG+HWC (0.81 kg N₂O-N ha^-1) and PRG+WC+P (0.85 kg N₂O-N ha^-1). This result was linked to a numerically lower fraction of nitrification (F_N) for PRG+WC+P potentially indicating that biological nitrification inhibition associated with ribwort plantain could lessen N₂O emissions. This study demonstrates some of the environmental benefits of grassland management systems that require less intensive chemical fertiliser N input.

含有草、固氮豆类和牧草的多品种牧场可以保持高草本干物质 (DM) 产量，同时减少对肥料 N 投入的需求，从而潜在地减少有害的 N 损失，例如一氧化二氮 (N ₂ O) 排放和硝酸盐 ( NO ₃ ^- ) 浸出到更广泛的环境中。然而，我们对组成对比鲜明的草原的这些过程的理解仍然非常有限。蒸渗仪实验进行了 12 个月，以检验仅来自多年生黑麦草 (PRG, 250 kg N ha ^-1 yr ^{-1 ) 的 (1) 累积和 (2) 季节性 N} ₂ O 排放和 N 浸出量最高的假设) 治疗与其他三种治疗相比；多年生黑麦草和低白三叶草 (PRG+LWC, 90 kg N ha ^-1 yr ^-1 )、多年生黑麦草和高白三叶草 (PRG+HWC, 0 kg N ha ^-1 yr ^-1 ) 和多年生黑麦草、白三叶草和Ribwort 车前草 (PRG+WC+P, 45 kg N ha ^-1 yr ^-1 ) 和 (3) 与这些 N 损失相关的土壤 N 循环途径（硝化/反硝化）在处理之间会有所不同。累积 N ₂ O 排放量 (2.74–3.25 kg N ₂ O-N ha ^-1 )、浸出 N (10.91–13.70 kg N ha ^-1 )、干物质产量 (5083–5493 kg DM ha ^-1 yr ^-1) 和 N 吸收 (122–169 kg N ha ^-1 yr ^-1 ) 在处理之间没有显着差异。与高施肥 N 输入 PRG 单一栽培相比，所有其他处理的氮产量按比例计算的 N ₂ O 排放量显着降低。处理和季节之间的显着交互作用表明，在春季， PRG（1.39 kg N ₂ O-N ha ^-1）和PRG+LWC（1.19 kg N ₂ O-N ha ^{-1 ）的N} ₂ O排放显着高于PRG+HWC（ 0.81 kg N ₂ O-N ha ^-1 ) 和 PRG+WC+P (0.85 kg N ₂ O-N ha ^-1）。这一结果与 PRG+WC+P 的数值较低的硝化分数 ( F _N ) 相关，这可能表明与车前草相关的生物硝化抑制可以减少 N ₂ O 排放。这项研究证明了草原管理系统的一些环境效益，这些系统需要较少的化学肥料 N 投入。