Grazed pasture constitutes a major source of agriculturally derived nitrous oxide (N₂O), which is a potent greenhouse gas. Soil texture and structure, soil moisture, and soil‐gas diffusivity are considered to be major soil physical drivers controlling pastoral N₂O emissions. Research gaps exist regarding their combined roles on N₂O emissions dynamics. This study used 2‐mm‐sieved and repacked soil samples, retrieved at three depths (0, 10, and 15 cm) from three grazed pasture sites in New Zealand, to investigate the combined effects of soil‐water characteristic (SWC) and soil‐gas diffusivity on N₂O emissions. The existing and modified parametric functions were used to numerically characterize and parameterize measured particle size distribution (PSD), SWC, and soil‐gas diffusivity. We observed distinct PSDs within the three soils with little variation across depths. Distinct fingerprints were observed for SWC and gas diffusivity in the three pasture soils, suggesting clear effects of soil type on diffusion‐controlled gas emissions. The soil moisture retention above approximately −10 kPa decreased with increasing depth and showed clear soil type effects. Soil‐gas diffusivity, on the other hand, showed pronounced depth‐wise variation below approximately −1000 kPa. Pore tortuosity was found to be nonlinearly correlated to air‐filled pore space as well as the PSD. The measured N₂O fluxes peaked around a diffusivity window of 0.005 to 0.01 for all soil types, and the corresponding water‐filled pore space ranged from 0.80 to 0.95. The results provide guidance for managing pasture soils to reduce high N₂O fluxes through reductions in compaction and excess irrigation such that the critical diffusivity window, where peak N₂O emissions occur, is avoided.

中文翻译：

---

土壤气体的扩散性和水分对重新包装草场土壤N2O排放的影响

放牧的草场是农业上产生的一氧化二氮（N ₂ O）的主要来源，一氧化二氮是一种有力的温室气体。土壤质地和结构，土壤水分和土壤气体扩散率被认为是控制牧草N ₂ O排放的主要土壤物理驱动力。关于它们在N ₂ O排放动力学中的综合作用，存在研究空白。这项研究使用了2毫米筛分和重新包装的土壤样本，这些样本是从新西兰三个放牧牧场的三个深度（0、10和15厘米）获取的，以调查土壤水特征（SWC）和土壤的综合影响N ₂上的气体扩散率O排放。现有的和修改后的参数函数用于对表征的粒度分布（PSD），SWC和土壤-气体扩散率进行数值表征和参数化。我们在三种土壤中观察到了不同的PSD，并且在深度上几乎没有变化。在三种牧场土壤中观察到了不同的指纹，表明SWC和气体扩散率不同，表明土壤类型对扩散控制的气体排放具有明显的影响。大约-10 kPa以上的土壤水分保持力随深度增加而降低，并表现出明显的土壤类型效应。另一方面，在大约-1000 kPa以下，土壤-气体扩散率显示出明显的深度变化。发现孔隙曲折度与充气孔隙空间以及PSD呈非线性关系。测得的N ₂对于所有类型的土壤，O通量均在0.005至0.01的扩散率窗口附近达到峰值，相应的充满水的孔隙空间在0.80至0.95之间。结果为通过减少压实和过度灌溉来管理牧场土壤以减少高N ₂ O通量提供了指导，从而避免了出现峰值N ₂ O排放的临界扩散率窗口。