Calibration of non-invasive fluorescence-based sensors for the manual and on-the-go assessment of grapevine vegetative status in the field

Background and Aims Optical sensors can accomplish frequent and spatially widespread non‐destructive monitoring of plant nutrient status. The main goal was to calibrate a fluorescence sensor, used both manually (MXH) and on‐the‐go (MXM), for the assessment of the spatial variability in the vineyard of the concentration of chlorophyll, flavonol and nitrogen in grapevine leaves, against that of a leaf‐clip type optical sensor (DX4). Methods and Results Measurements were taken in a commercial vineyard on the adaxial and abaxial sides of leaves of nine Vitis vinifera L. cultivars, manually with the DX4 and MXH, and with the MXM mounted on an all‐terrain vehicle. A significant correlation was obtained for the chlorophyll and nitrogen indices of MXH and DX4 (R2 > 0.90) and of MXM and DX4 (R2 > 0.74), and the calibration equations were defined. A similar spatial distribution was achieved for the chlorophyll, flavonol and nitrogen indices of the leaves. Conclusions The capability of the fluorescence sensor, used manually and on‐the‐go, for characterising the nutritional status of grapevines was demonstrated. Significance of the Study This work reports the first calibration of the hand‐held and on‐the‐go fluorescence sensor to assess key nutritional parameters of grapevines. The applicability of this sensor on‐the‐go to characterise the spatial variability of the vegetative status of a vineyard for the delineation of homogeneous management zones was proved.