Research is lacking monitoring beyond the root zone for programmatic or regulatory assessment and for onsite monitoring of field‐ or farm scale agricultural nitrate leaching to groundwater. Here, we investigate the relationship between measurements of N at the sediment core scale, the groundwater monitoring well scale, and the field or farm management scale. Importantly, we monitor across the vertical continuum of root zone (RZ, to 3 m), deep vadose zone (DVZ, to 7 m), and upper saturated zone (SZ, to 14 m) in a highly heterogeneous alluvial sediment system, common to many agricultural groundwater basins. Twenty 14‐m‐deep sediment cores collected across a 56‐ha commercial almond orchard were characterized for texture, water content, nitrate, and ammonium. Groundwater nitrate samples (GW) were also obtained from monitoring wells installed and screened across the SZ at the coring sites. Measured parameters were found highly variable at the 0.05‐m core sample scale. Monitoring well nitrate concentrations also span over a half order of magnitude despite the uniform agronomic practices across the orchard. Laterally aggregated, orchard‐scale parameter means exhibited significant vertical trends and differed in variability between RZ, DVZ, and SZ. Within the SZ, coarse texture facies nitrate concentrations were most closely correlated to GW nitrate, confirming the significance of preferential flow paths within the SZ. The data also indicate significant correlation between DVZ and GW nitrate concentrations. Our findings have important implications to developing appropriate onsite monitoring tools of field‐ or farm‐scale N emissions to groundwater.

中文翻译：

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测量从田间到农场规模的关键区域的硝酸盐浸出量

缺乏对根部区域以外的项目进行方案或法规评估以及对田间或农场规模的农业硝酸盐向地下水的淋失进行现场监测的研究。在这里，我们调查了在沉积物核心规模，地下水监测井规模以及田间或农场经营规模的氮测量之间的关系。重要的是，我们在高度非均质冲积沉积物系统中，监测根区（RZ，至3 m），深渗流区（DVZ，至7 m）和上饱和区（SZ，至14 m）的垂直连续体，这很常见。到许多农业地下水盆地。在一个56公顷的商业杏仁果园中收集了20个深14微米的沉积物岩心，进行了质地，水含量，硝酸盐和铵盐的表征。地下水硝酸盐样品（GW）也可以从在取样区整个SZ进行安装和筛选的监测井中获得。发现测得的参数在核心样品规模为0.05-m时变化很大。尽管果园采取了统一的农艺措施，但监测井中硝酸盐的浓度也跨越了一半数量级。横向汇总的果园规模参数均值显示出显着的垂直趋势，并且RZ，DVZ和SZ之间的变异性不同。在深圳内，粗质地相的硝酸盐浓度与GW硝酸盐最密切相关，证实了深圳内优先流动路径的重要性。数据还表明DVZ和GW硝酸盐浓度之间存在显着相关性。