Optimal timing of nitrogen (N) fertilizer to promote N use efficiency (NUE) in cool climate wine regions is largely unknown. One year-old potted Vitis vinifera L. (Vitaceae) cv. Pinot Noir vines were subjected to soil applied ¹⁵N-labelled calcium nitrate (5.5 atom%) fertilizer at four application timings (budbreak to fruit set, fruit set to veraison, veraison to harvest, or spread evenly across the growing season) over two growing seasons (2017/18 and 2018/19) at a rate of 12 g N vine⁻¹. Annual vine parts (leaves and clusters) were collected at commercial harvest in both 2018 and 2019 and the remaining vine was destructively harvested during winter dormancy. Vines were separated into organs (leaves, clusters, shoot, trunk, and roots) and organ dry matter was determined before samples were ground into a fine powder to determine total N percentage and ¹⁵N atom percentage using flash combustion isotope ratio mass spectrometry (varioPYRO cube coupled to Isoprime100 mass spectrometer). Compared to the average values obtained from the other treatments, the veraison to harvest treatment significantly reduced whole vine dry matter by 39.1% and vine NUE by 42.1%. Yield was also reduced by 12.9% compared to the budbreak to fruit set treatment. NDF, defined here as the proportion of N within the vine (or vine organ) that was derived from fertilizer N, and overall vine total N content was lower in the veraison to harvest treatment due to the reduction of root and shoot NDF content. This suggests that for young, actively growing vines in cool climates, limiting N applications until veraison is inefficient and ineffective. No significant differences in NUE, N partitioning or N storage were observed between the other fertilizer N application timings.

在凉爽气候的葡萄酒产区，氮肥 (N) 施肥以提高氮利用效率 (NUE) 的最佳时机在很大程度上是未知的。一岁盆栽Vitis vinifera L. (Vitaceae) cv。黑比诺葡萄藤在四个施用时间（萌芽到坐果、坐果到转色、转色到收获或在整个生长季节均匀分布）施以¹⁵ N 标记的硝酸钙（5.5 原子％）肥料，在两次生长期间季节（2017/18 和 2018/19）以 12 g N vine ^-1的速率. 一年生葡萄树部分（叶子和簇）在 2018 年和 2019 年的商业收获时被收集，剩余的葡萄树在冬季休眠期间被破坏性地收获。将葡萄藤分为器官（叶、簇、枝条、树干和根），并在将样品研磨成细粉之前测定器官干物质，以确定总 N 百分比和¹⁵使用闪燃同位素比质谱法（varioPYRO 立方体与 Isoprime100 质谱仪耦合）的 N 原子百分比。与从其他处理获得的平均值相比，收获处理使整个葡萄树干物质显着减少了 39.1%，葡萄树 NUE 减少了 42.1%。与从萌芽到坐果的处理相比，产量也降低了 12.9%。NDF，这里定义为来自肥料 N 的葡萄树（或葡萄树器官）中 N 的比例，由于根和芽 NDF 含量的减少，葡萄树总 N 含量在收获处理到收获处理中较低。这表明，对于凉爽气候中年轻、积极生长的葡萄藤，限制施氮直至变质效率低下。NUE无显着差异，