Nitrate leaching is an important yet difficult to manage contribution to groundwater and surface water contamination in agricultural areas. We examined 14 farm fields over a four year period (2014–2017) in the southern Willamette Valley, providing 53 sets of annual, field-level agricultural performance metrics related to nitrogen (N), including fertilizer inputs, crop harvest outputs, N use efficiency (NUE), nitrate–N leaching and surplus N. Crop-specific nitrate–N leaching varied widely from 10 kg N ha⁻¹ yr⁻¹ in hazelnuts to > 200 kg N ha⁻¹ yr⁻¹ in peppermint. Averaging across all sites and years, most leaching occurred during fall (60%) and winter (32%). Overall NUE was 57%. We used a graphical approach to explore the relationships between N inputs, surplus, crop N harvest removal and NUE by crop type. The blueberry site had high inputs and surplus, peppermint had high inputs but also high crop N removal and NUE and thus lower surplus, and most wheat crops had high NUE and evidence of using soil N. Annual N surplus was not well correlated with leaching, and leaching varied more by crop type and inputs. Grass seed and hazelnuts, which are dominant crop types in the southern Willamette Valley, were intermediate in terms of NUE, leaching and surplus. Of all performance metrics, N input was most closely aligned with field-level crop N harvest and nitrate leaching, therefore optimizing N inputs may well inform local efforts to reduce groundwater nitrate contamination.

硝酸盐浸出是农业地区地下水和地表水污染的一个重要但难以管理的贡献。我们在四年期间（2014-2017 年）检查了威拉米特山谷南部的 14 个农田，提供了 53 组与氮 (N) 相关的年度田间农业绩效指标，包括肥料投入、作物收获产出、氮利用效率 (NUE)、硝酸盐-N 浸出和剩余 N。作物特定的硝酸盐-N 浸出变化很大，从榛子中的 10 kg N ha ^-1 yr ^-1到 > 200 kg N ha ^-1 yr ^-1在薄荷。平均所有地点和年份，大部分浸出发生在秋季（60%）和冬季（32%）。总体 NUE 为 57%。我们使用图形方法来探索不同作物类型的 N 投入、剩余、作物 N 收获去除和 NUE 之间的关系。蓝莓场地有高投入和盈余，薄荷投入高，但作物氮去除和 NUE 也高，因此盈余较低，大多数小麦作物的 NUE 较高，并且有证据表明使用土壤 N。年度 N 盈余与淋失没有很好的相关性，浸出量因作物类型和投入而异。草籽和榛子是威拉米特山谷南部的主要作物类型，在 NUE、浸出和过剩方面处于中等水平。在所有绩效指标中，氮输入与田间作物氮收获和硝酸盐浸出最接近，