Scientific and reasonable application of nitrogen fertiliser is an important agronomic measure to achieve both a high yield and a high quality of malting barley, and determining the appropriate nitrogen concentration is important for optimising the two. To this end, we constructed critical concentration curves for plant and ear nitrogen of malting barley as a tool for diagnosing nitrogen nutrition. Two varieties of barley, Zhepi 33 and Yangnongpi 8, were used as experimental materials, and five nitrogen application levels (ranging from 0 to 300 kg·ha^–1) were established in three field experiments. Plant dry matter first increased and then stabilised and the nitrogen concentration increased continuously with an increase in nitrogen application rate. Based on analyses of the relationship between dry matter and nitrogen concentration, dilution models of critical nitrogen concentration in the plant (Np) and ear (Ne) of malting barley were established, and were expressed as power function equations: Np = 3.879PDM^–0.444 (R² = 0.9705) and Ne = 2.198EDM^–0.152 (R² = 0.7968). Next, nitrogen nutrition indexes were constructed to identify nitrogen-limiting and non-limiting treatments. To ensure an optimal grain protein concentration of 10–12%, the Ne index and the Np index were required to be 0.897–1.061 and 0.699–0.992 at the heading stage, respectively. The results provide a theoretical foundation for the diagnosis and regulation of nitrogen nutrition in malting barley and have great significance for the production of high-quality and high-yielding malting barley.

科学合理施用氮肥是实现大麦高产优质的重要农艺措施，确定适宜的氮肥浓度对优化两者具有重要意义。为此，我们构建了大麦麦芽植物和穗氮的临界浓度曲线，作为氮营养诊断的工具。以浙皮33和羊农皮8两个品种为试验材料，施氮5个水平（0～300 kg·ha ^–1) 是在三个现场实验中建立的。随着施氮量的增加，植物干物质先增加后稳定，施氮量不断增加。在分析干物质与氮浓度关系的基础上，建立了大麦麦芽植株（Np）和穗（Ne）临界氮浓度的稀释模型，并表示为幂函数方程：Np = 3.879PDM ^–0.444 (R ² = 0.9705) 和 Ne = 2.198EDM ^–0.152 (R ²= 0.7968）。其次，构建氮营养指数来识别限氮和非限氮处理。为确保最佳籽粒蛋白浓度为 10-12%，抽穗期的 Ne 指数和 Np 指数分别为 0.897-1.061 和 0.699-0.992。研究结果为大麦麦芽氮营养的诊断和调控提供了理论依据，对生产优质高产大麦麦芽具有重要意义。