Nitrous oxide (N2 O) is an air pollutant of major environmental concern, with agriculture representing 60% of anthropogenic global N2 O emissions. Much of the N2 O emissions from livestock production systems result from transformation of N deposited to soil within animal excreta. There exists a substantial body of literature on urine patch N2 O dynamics, we aimed to identify key controlling factors influencing N2 O emissions and to aid understanding of knowledge gaps to improve GHG reporting and prioritize future research. We conducted an extensive literature review and random effect meta-analysis (using REML) of results to identify key relationships between multiple potential independent factors and global N2 O emissions factors (EFs) from urine patches. Mean air temperature, soil pH and ruminant animal species (sheep or cow) were significant factors influencing the EFs reviewed. However, several factors that are known to influence N2 O emissions, such as animal diet and urine composition, could not be considered due to the lack of reported data. The review highlighted a widespread tendency for inadequate metadata and uncertainty reporting in the published studies, as well as the limited geographical extent of investigations, which are more often conducted in temperate regions thus far. Therefore, here we give recommendations for factors that are likely to affect the EFs and should be included in all future studies, these include the following: soil pH and texture; experimental set-up; direct measurement of soil moisture and temperature during the study period; amount and composition of urine applied; animal type and diet; N2 O emissions with a measure of uncertainty; data from a control with zero-N application and meteorological data.

中文翻译：

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全球农业土壤中牲畜尿液产生的一氧化二氮排放量的荟萃分析。

一氧化二氮 (N2 O) 是一种引起主要环境问题的空气污染物，农业排放的 N2 O 占全球人为排放的 60%。畜牧生产系统排放的大部分 N2 O 是由动物排泄物中沉积到土壤中的氮转化造成的。关于尿斑 N2 O 动力学存在大量文献，我们的目的是确定影响 N2 O 排放的关键控制因素，并帮助了解知识差距，以改进温室气体报告并优先考虑未来的研究。我们对结果进行了广泛的文献综述和随机效应荟萃分析（使用 REML），以确定多个潜在独立因素与尿斑中的全球 N2 O 排放因素 (EF) 之间的关键关系。平均气温、土壤 pH 值和反刍动物种类（绵羊或牛）是影响所审查的 EF 的重要因素。然而，由于缺乏报告数据，无法考虑一些已知影响 N2 O 排放的因素，例如动物饮食和尿液成分。该审查强调了已发表研究中元数据和不确定性报告不足的普遍趋势，以及调查的地理范围有限，迄今为止，调查通常在温带地区进行。因此，我们在这里对可能影响 EF 的因素提出建议，并应将其纳入所有未来的研究中，其中包括：土壤 pH 值和质地；实验装置; 研究期间直接测量土壤湿度和温度；所用尿液的量和成分；动物类型和饮食；N2 O 排放量具有一定的不确定性；来自零氮应用和气象数据的控制的数据。