Background: The current method employed by industry for tissue analysis to determine grapevine nitrogen (N) status is expensive and time intensive. Aims: This study explored the use of proximal sensors and Fourier transform near infrared spectroscopy (FT‐NIRS) to predict vine (Vitis vinifera L.) canopy N status over two growing seasons in Southern Tasmania, Australia. Methods: The GreenSeeker, Crop Circle ACS‐430 and SPAD‐502 proximal sensors were used to measure vine canopies (cv. Pinot Noir and Chardonnay) at three sampling dates (January, February, March) in the 2017/18 growing season, and two (December & February) in the 2018/19 growing season. For 12 replicates consisting of 5 vines each, a 30‐leaf sample was taken for FT‐NIRS and elemental analysis on dried, ground leaf samples. In addition, measurements with a portable FT‐NIRS were taken on fresh leaf samples (2018/19). All measurements were correlated with leaf N concentration (%) determined via elemental analysis. Results: The reliability of the proximal sensors to predict vine N content was dependent on the vine variety and sampling time. FT‐NIRS demonstrated a strong ability to predict vine N concentration independent of season, sampling time and variety. The benchtop FT‐NIRS showed the strongest predictability over both seasons (r2 = 0.94), yet the portable FT‐NIRS also showed potential (r2 = 0.76). Conclusion: Further investigation of portable FT‐NIRS technology is necessary to provide a robust model for non‐destructive vine N determination in the field.

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Low yeast assimilable nitrogen (YAN) concentrations (<140 mg/N/L) can produce wines with inferior aroma and flavor, regardless of supplemental nitrogen (N) additions in the winery. The impact of doubling commercial field N and irrigation rates was explored in Vitis vinifera L. cv. Chardonnay and Pinot noir over three growing seasons (2016 to 2019) in Southern Tasmania, Australia, to improve YAN concentrations and observe the concurrent influence on vine canopy, yield, and grape and wine composition. Six combinations of irrigation and N rates were applied to 20 vines for each treatment combination and replicated across both cultivars. The treatments included the standard irrigation rate (~530 L/vine/year) / control N (0 kg/N/ha/year) rate, standard irrigation / standard commercial N rate (~18 kg/N/ha/year), standard irrigation / double commercial N rate (~36 kg/N/ha/ year), double irrigation rate (~1060 L/vine/year) / control N, double irrigation / standard N, and double irrigation / double N. Analysis of variance was used to determine main treatment effects and treatment interactions of the measured variables for a subset of the vine population in each growing season. Increasing N rate improved YAN concentrations in both cultivars in two of three growing seasons, with the double N rate associated with increasing YAN to acceptable (>140 mg/N/L) levels. Irrigation had no impact on YAN concentrations. Treatment influences on vine vegetative growth, yield, and grape and wine composition were marginal, inconsistent, and largely influenced by climatic conditions. Cool-climate grapegrowers would benefit from applying more N in the vineyard around veraison to improve YAN without stimulating vigor or reducing the quality of grape and wine chemical composition. Increasing irrigation rates may be advantageous in seasons with high crop load; however, current commercial irrigation rates are considered adequate.

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