Performance of reflectance indices and of a handheld device for estimating in‐field the nitrogen status of grapevine leaves

• M. Friedel ^[1] ; M. Hendgen ^[1] ; M. Stoll ^[1] ; O. Löhnertz ^[1]
  1. [1] Hochschule Geisenheim University

     Hochschule Geisenheim University

     Rheingau-Taunus-Kreis, Alemania

     
• Localización: Australian journal of grape and wine research, ISSN 1322-7130, Vol. 26, Nº 2, 2020, págs. 110-120
• Idioma: inglés
• Texto completo no disponible (Saber más ...)
• Resumen

  • 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.