Fertilizer nitrogen (N) management in any region following standard general recommendations discount the fact that crop response to N varies between sites and seasons. To devise field-specific N management in wheat at jointing stage (Feekes 6 growth stage) using atLeaf meter and leaf colour chart (LCC), eight field experiments were conducted in three wheat seasons during 2017–2020 in the West Delta of Egypt. In the first two seasons, four experiments consisted of treatments with a range of fertilizer N application levels from 0 to 320 kg N ha−1. Monitoring atLeaf and LCC measurements at Feekes 6 growth stage in plots with different yield potentials allowed formulation of different criteria to apply field-specific and crop need-based fertilizer N doses. In the four experiments conducted in the third season in 2019/20, different field-specific N management strategies formulated in 2017/18 and 2018/19 wheat seasons were evaluated. In the atLeaf-based fertilizer N management experiment, prescriptive application of 40 kg N ha−1 at 10 days after seeding (DAS) and 60 kg N ha−1 at 30 DAS followed by application of an adjustable dose at Feekes 6 stage computed by multiplying the difference of atLeaf measurements of the test plot and the N-sufficient plot with 42.25 (as derived from the functional model developed in this study), resulted in grain yield similar or higher to that obtained by following the standard treatment. The LCC-based strategy to apply field-specific fertilizer N at Feekes 6 stage consisted of applying 150, 100 or 0 kg N ha−1 based on LCC shade equal to or less than 4, between 4 and 5 or equal to or more than 5, respectively. Both atLeaf- and LCC-based fertilizer N management strategies not only recorded the highest grain yield levels but also resulted in higher use efficiency with 57–60 kg N ha−1 in average less fertilizer use than the standard treatment.

遵循标准一般建议的任何地区的肥料氮 (N) 管理忽略了作物对 N 的反应因地点和季节而异的事实。为了使用 atLeaf 测量仪和叶色图 (LCC) 设计拔节期（Feekes 6 生长阶段）小麦田间特定的氮管理，在 2017-2020 年期间在埃及西部三角洲的三个小麦季节进行了八次田间试验。在前两个季节，四个试验包括使用范围从 0 到 320 kg N ha -1 的施氮水平的处理. 在具有不同产量潜力的地块中监测 Feekes 6 生长阶段的 atLeaf 和 LCC 测量值，允许制定不同的标准，以应用田间特定的和基于作物需求的氮肥剂量。在 2019/20 年度第三季进行的四个试验中，评估了 2017/18 和 2018/19 小麦季节制定的不同田间特定氮管理策略。在基于 atLeaf 的氮肥管理实验中，在播种后 10 天（DAS）规定施用 40 kg N ha -1和 60 kg N ha -1在 30 DAS，然后在 Feekes 6 阶段应用可调剂量，通过将测试图和 N 充足图的 atLeaf 测量值的差异乘以 42.25（源自本研究开发的功能模型）计算得出谷物产量与按照标准处理获得的产量相似或更高。在 Feekes 6 阶段施用田间特定肥料 N 的基于 LCC 的策略包括基于 LCC 阴影等于或小于 4、4 和 5 之间或等于或大于施用 150、100 或 0 kg N ha -1 5、分别。基于 atLeaf 和 LCC 的氮肥管理策略不仅记录了最高的谷物产量水平，而且使用效率更高，为 57-60 kg N ha -1 化肥用量平均低于标准处理。