Background and Aims Optical leaf sensing of plant nitrogen (N) status enables fertilisation based on plant demand. The aim of this study was to assess the suitability of leaf reflectance indices and of a handheld device for the estimation of N and chlorophyll (Chl) in Vitis vinifera L. cv. Riesling. Methods and Results Riesling leaves from a long‐term fertilisation trial were analysed for nitrogen and pigments and their spectral reflectance in the Vis/near‐infrared range was recorded for two consecutive seasons. In the second season the leaves were also measured with a Chl fluorescence based portable device (Dualex). Published reflectance indices and fluorescence indices were regressed against the concentration of pigment and N. Temporal changes in the Chl/N ratio complicated the indirect assessment of N via Chl. Red edge inflection points and several three‐ to four‐waveband indices allowed for a good prediction of leaf N. Fluorescence indices allowed for reliable estimation of N and Chl. Conclusions While leaf pigments can be analysed by simple two‐band indices, accurate N estimation requires more complex indices such as three‐band indices or indices calculated from derivative spectra. Significance of the Study Data from this study will assist growers to monitor non‐destructively the spatial and temporal variability of grapevine N status and thereby, improve fertilisation.

中文翻译：

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反射指数的性能和用于估计葡萄叶片田间氮状态的手持设备的性能

背景和目标 植物氮 (N) 状态的光学叶片感应能够根据植物需求进行施肥。本研究的目的是评估叶片反射指数和手持设备对估计 Vitis vinifera L. cv. 中 N 和叶绿素 (Chl) 的适用性。雷司令。方法和结果 对来自长期施肥试验的雷司令叶子进行氮和色素分析，并连续两个季节记录它们在可见光/近红外范围内的光谱反射率。在第二个季节，叶子也用基于 Chl 荧光的便携式设备 (Dualex) 进行了测量。已公布的反射指数和荧光指数根据色素和 N 的浓度进行回归。 Chl/N 比率的时间变化使通过 Chl 间接评估 N 变得复杂。红边拐点和几个三到四波段指数可以很好地预测叶 N。荧光指数可以可靠地估计 N 和 Chl。结论虽然可以通过简单的双波段指数分析叶色素，但准确的 N 估计需要更复杂的指数，例如三波段指数或从导数光谱计算的指数。来自本研究的研究数据的意义将帮助种植者无损监测葡萄 N 状态的时空变异性，从而改善施肥。准确的 N 估计需要更复杂的指数，例如三波段指数或从导数谱计算的指数。来自本研究的研究数据的意义将帮助种植者无损监测葡萄 N 状态的时空变异性，从而改善施肥。准确的 N 估计需要更复杂的指数，例如三波段指数或从导数谱计算的指数。来自本研究的研究数据的意义将帮助种植者无损监测葡萄 N 状态的时空变异性，从而改善施肥。