**Figure 1.**
Seasonal variation of the Greenness Index (SPAD) measured on leaves of Barbera vines subjected to different nitrogen fertilization (N+ versus N0), for each trial year (2016–2017–2018). (**A**): 2016, basal; (**B**): 2016, median; (**C**): 2016, apical; (**D**): 2017, basal; (**E**): 2017, median; (**F**): 2017, apical; (**G**): 2018, basal; (**H**): 2018, median; (**I**): 2018, apical. First fertilization: 23 May 2016 (day of the year (DOY)) 144), 28 April 2017 (DOY 118), 7 May 2018 (DOY 127). Within each sampling date, the asterisk indicates significant differences among vigor levels at p < 0.05 according to the Student–Newman–Keuls (SNK) test. Vertical bars indicate standard error (SE).

**Figure 1.**
Seasonal variation of the Greenness Index (SPAD) measured on leaves of Barbera vines subjected to different nitrogen fertilization (N+ versus N0), for each trial year (2016–2017–2018). (**A**): 2016, basal; (**B**): 2016, median; (**C**): 2016, apical; (**D**): 2017, basal; (**E**): 2017, median; (**F**): 2017, apical; (**G**): 2018, basal; (**H**): 2018, median; (**I**): 2018, apical. First fertilization: 23 May 2016 (day of the year (DOY)) 144), 28 April 2017 (DOY 118), 7 May 2018 (DOY 127). Within each sampling date, the asterisk indicates significant differences among vigor levels at p < 0.05 according to the Student–Newman–Keuls (SNK) test. Vertical bars indicate standard error (SE).

**Figure 2.**
Seasonal variation of the assimilation rate measured on leaves of Barbera vines subjected to different nitrogen fertilization (N+ versus N0), for each trial year (2016–2017–2018). (**A**): 2016, basal; (**B**): 2016, median; (**C**): 2016, apical; (**D**): 2017, basal; (**E**): 2017, median; (**F**): 2017, apical; (**G**): 2018, basal; (**H**): 2018, median; (**I**): 2018, apical. First fertilization: 23 May 2016 (DOY 144), 28 April 2017 (DOY 118), 7 May 2018 (DOY 127). Within each sampling date, the asterisk indicates significant differences among vigor levels at p < 0.05 according to the Student–Newman–Keuls (SNK) test. Vertical bars indicate SE.

**Figure 2.**
Seasonal variation of the assimilation rate measured on leaves of Barbera vines subjected to different nitrogen fertilization (N+ versus N0), for each trial year (2016–2017–2018). (**A**): 2016, basal; (**B**): 2016, median; (**C**): 2016, apical; (**D**): 2017, basal; (**E**): 2017, median; (**F**): 2017, apical; (**G**): 2018, basal; (**H**): 2018, median; (**I**): 2018, apical. First fertilization: 23 May 2016 (DOY 144), 28 April 2017 (DOY 118), 7 May 2018 (DOY 127). Within each sampling date, the asterisk indicates significant differences among vigor levels at p < 0.05 according to the Student–Newman–Keuls (SNK) test. Vertical bars indicate SE.

**Figure 3.**
Seasonal variation of stomatal conductance (g_{s}) measured on leaves of Barbera vines subjected to different nitrogen fertilization (N+ versus N0), for each trial year (2016–2017–2018). (**A**): 2016, basal; (**B**): 2016, median; (**C**): 2016, apical; (**D**): 2017, basal; (**E**): 2017, median; (**F**): 2017, apical; (**G**): 2018, basal; (**H**): 2018, median; (**I**): 2018, apical. First fertilization: 23 May 2016 (DOY 144), 28 April 2017 (DOY 118), 7 May 2018 (DOY 127). Within each sampling date, the asterisk indicates significant differences among vigor levels at p < 0.05 according to the Student–Newman–Keuls (SNK) test. Vertical bars indicate SE.

**Figure 3.**
Seasonal variation of stomatal conductance (g_{s}) measured on leaves of Barbera vines subjected to different nitrogen fertilization (N+ versus N0), for each trial year (2016–2017–2018). (**A**): 2016, basal; (**B**): 2016, median; (**C**): 2016, apical; (**D**): 2017, basal; (**E**): 2017, median; (**F**): 2017, apical; (**G**): 2018, basal; (**H**): 2018, median; (**I**): 2018, apical. First fertilization: 23 May 2016 (DOY 144), 28 April 2017 (DOY 118), 7 May 2018 (DOY 127). Within each sampling date, the asterisk indicates significant differences among vigor levels at p < 0.05 according to the Student–Newman–Keuls (SNK) test. Vertical bars indicate SE.

**Figure 4.**
Seasonal variation of the t-value relative to the comparison between the foliar reflectance values of the N+ versus N0 treatments for each wavelength of the electromagnetic spectrum Vis-NIR. (**A**): 2016, basal; (**B**): 2016, median; (**C**): 2016, apical; (**D**): 2017, basal; (**E**): 2017, median; (**F**): 2017, apical; (**G**): 2018, basal; (**H**): 2018, median; (**I**): 2018, apical. First fertilization: 23 May 2016 (DOY 144), 28 April 2017 (DOY 118), 7 May 2018 (DOY 127).

**Figure 4.**
Seasonal variation of the t-value relative to the comparison between the foliar reflectance values of the N+ versus N0 treatments for each wavelength of the electromagnetic spectrum Vis-NIR. (**A**): 2016, basal; (**B**): 2016, median; (**C**): 2016, apical; (**D**): 2017, basal; (**E**): 2017, median; (**F**): 2017, apical; (**G**): 2018, basal; (**H**): 2018, median; (**I**): 2018, apical. First fertilization: 23 May 2016 (DOY 144), 28 April 2017 (DOY 118), 7 May 2018 (DOY 127).

**Figure 5.**
Seasonal variation in 2016 of the t-value relative to the comparison between the values of broadband vegetation indices of the N+ versus N0 treatments. In black is presented the standard NDVI, in red are reported indices based on two bands and in blue indices based on three bands. Linear pattern when the t-value is below the threshold of significance, full color when significant. (**A**): DOY 145-basal; (**B**): DOY 145-median; (**C**): DOY 145-apical; (**D**): DOY 159-basal; (**E**): DOY 159-median; (**F**): DOY 159-apical; (**G**): DOY 172-basal; (**H**): DOY 172-median; (**I**): DOY 172-apical; (**L**): DOY 180-basal; (**M**): DOY 180-median; (**N**): DOY 180-apical. Indices highlighted were then correlated with N content (Figure 8).

**Figure 5.**
Seasonal variation in 2016 of the t-value relative to the comparison between the values of broadband vegetation indices of the N+ versus N0 treatments. In black is presented the standard NDVI, in red are reported indices based on two bands and in blue indices based on three bands. Linear pattern when the t-value is below the threshold of significance, full color when significant. (**A**): DOY 145-basal; (**B**): DOY 145-median; (**C**): DOY 145-apical; (**D**): DOY 159-basal; (**E**): DOY 159-median; (**F**): DOY 159-apical; (**G**): DOY 172-basal; (**H**): DOY 172-median; (**I**): DOY 172-apical; (**L**): DOY 180-basal; (**M**): DOY 180-median; (**N**): DOY 180-apical. Indices highlighted were then correlated with N content (Figure 8).

**Figure 6.**
Seasonal variation in 2017 of the t-value relative to the comparison between the values of broadband vegetation indices of the N+ versus N0 treatments. In black is presented the standard NDVI, in red are reported indices based on two bands and in blue indices based on three bands. Linear pattern when the t-value is below the threshold of significance, full color when significant. (**A**): DOY 129-basal; (**B**): DOY 129-median; (**C**): DOY 137-basal; (**D**): DOY 137-median; (**E**): DOY 144-basal; (**F**): DOY 144-median; (**G**): DOY 144-apical; (**H**): DOY 177-basal; (**I**): DOY 177-median; (**L**): DOY 177-apical. Indices highlighted were then correlated with N content (Figure 8).

**Figure 6.**
Seasonal variation in 2017 of the t-value relative to the comparison between the values of broadband vegetation indices of the N+ versus N0 treatments. In black is presented the standard NDVI, in red are reported indices based on two bands and in blue indices based on three bands. Linear pattern when the t-value is below the threshold of significance, full color when significant. (**A**): DOY 129-basal; (**B**): DOY 129-median; (**C**): DOY 137-basal; (**D**): DOY 137-median; (**E**): DOY 144-basal; (**F**): DOY 144-median; (**G**): DOY 144-apical; (**H**): DOY 177-basal; (**I**): DOY 177-median; (**L**): DOY 177-apical. Indices highlighted were then correlated with N content (Figure 8).

**Figure 7.**
Seasonal variation in 2018 of the t-value relative to the comparison between the values of broadband vegetation indices of the N+ versus N0 treatments. In black is presented the standard NDVI, in red are reported indices based on two bands and in blue indices based on three bands. Linear pattern when the t-value is below the threshold of significance, full color when significant. (**A**): DOY 130-basal; (**B**): DOY 130-median; (**C**): DOY 138-basal; (**D**): DOY 138-median; (**E**): DOY 152-basal; (**F**): DOY 152-median; (**G**): DOY 152-apical; (**H**): DOY 169-basal; (**I**): DOY 169-median; (**L**): DOY 169-apical. Indices highlighted were then correlated with N content (Figure 8).

**Figure 7.**
Seasonal variation in 2018 of the t-value relative to the comparison between the values of broadband vegetation indices of the N+ versus N0 treatments. In black is presented the standard NDVI, in red are reported indices based on two bands and in blue indices based on three bands. Linear pattern when the t-value is below the threshold of significance, full color when significant. (**A**): DOY 130-basal; (**B**): DOY 130-median; (**C**): DOY 138-basal; (**D**): DOY 138-median; (**E**): DOY 152-basal; (**F**): DOY 152-median; (**G**): DOY 152-apical; (**H**): DOY 169-basal; (**I**): DOY 169-median; (**L**): DOY 169-apical. Indices highlighted were then correlated with N content (Figure 8).

**Figure 8.**
Within-year correlation between index reflectance and leaf N concentration and selected 12 broadband vegetation indices evaluated for data pooled over N+ and N0. Index values were DOY 172, 177, and 169 in 2016, 2017, and 2018, respectively. △: 2016-N0; ▲: 2016-N+; □: 2017-N0; ■: 2017-N+; ○: 2018-N0; ●: 2018-N+. Individual regression formulae are provided below. (**A**): 2016, y = 2.09x − 1.25 (R^{2} = 0.91); 2017, y = 1.32x − 0.51 (R^{2} = 0.96); 2018, y = 1.12x + 0.53 (R^{2} = 0.69). (**B**): 2016, y = 1.68x − 1.01 (R^{2} = 0.91); 2017, y = 1.02x − 0.27 (R^{2} = 0.96); 2018, y = 0.90x + 0.64 (R^{2} = 0.69). (**C**): 2016, y = 13.04x − 3.68 (R^{2} = 0.90); 2017, y = 9.23x − 2.46 (R^{2} = 0.96); 2018, y = 5.68x − 0.24 (R^{2} = 0.66). (**D**): 2016, y = 11.87x − 3.59 (R^{2} = 0.89); 2017, y = 8.22x − 2.29 (R^{2} = 0.95); 2018, y = 5.04x − 0.14 (R^{2} = 0.65). (**E**): 2016, y = 16.07x − 4.38 (R^{2} = 0.92); 2017, y = 11.20x − 2.93 (R^{2} = 0.95); 2018, y = 6.59x − 0.39 (R^{2} = 0.62). (**F**): 2016, y = 13.93x − 4.07 (R^{2} = 0.91); 2017, y = 9.38x − 2.53 (R^{2} = 0.95); 2018, y = 5.63x − 0.23 (R^{2} = 0.62). (**G**): 2016, y = 0.70x − 0.05 (R^{2} = 0.44); 2017, y = 0.66x − 0.31 (R^{2} = 0.93); 2018, y = 0.48x + 0.81 (R^{2} = 0.59). (**H**): 2016, y = 0.62x − 0.03 (R^{2} = 0.48); 2017, y = 0.53x − 0.12 (R^{2} = 0.93); 2018, y = 0.41x + 0.87 (R^{2} = 0.60). (**I**): 2016, y = 1.10x − 0.52 (R^{2} = 0.91); 2017, y = 0.75x − 0.12 (R^{2} = 0.96); 2018, y = 0.72x + 0.66 (R^{2} = 0.71). (**L**): 2016, y = 0.90x − 0.38 (R^{2} = 0.90); 2017, y = 0.59x + 0.05 (R^{2} = 0.95); 2018, y = 0.59x + 0.76 (R^{2} = 0.71). (**M**): 2016, y = 0.31x − 1.06 (R^{2} = 0.87); 2017, y = 0.27x − 1.03 (R^{2} = 0.94); 2018, y = 0.11x + 1.18 (R^{2} = 0.61). (**N**): 2016, y = 0.27x − 1.35 (R^{2} = 0.86); 2017, y = 0.21x − 0.98 (R^{2} = 0.94); 2018, y = 0.09x + 1.07 (R^{2} = 0.61).

**Figure 8.**
Within-year correlation between index reflectance and leaf N concentration and selected 12 broadband vegetation indices evaluated for data pooled over N+ and N0. Index values were DOY 172, 177, and 169 in 2016, 2017, and 2018, respectively. △: 2016-N0; ▲: 2016-N+; □: 2017-N0; ■: 2017-N+; ○: 2018-N0; ●: 2018-N+. Individual regression formulae are provided below. (**A**): 2016, y = 2.09x − 1.25 (R^{2} = 0.91); 2017, y = 1.32x − 0.51 (R^{2} = 0.96); 2018, y = 1.12x + 0.53 (R^{2} = 0.69). (**B**): 2016, y = 1.68x − 1.01 (R^{2} = 0.91); 2017, y = 1.02x − 0.27 (R^{2} = 0.96); 2018, y = 0.90x + 0.64 (R^{2} = 0.69). (**C**): 2016, y = 13.04x − 3.68 (R^{2} = 0.90); 2017, y = 9.23x − 2.46 (R^{2} = 0.96); 2018, y = 5.68x − 0.24 (R^{2} = 0.66). (**D**): 2016, y = 11.87x − 3.59 (R^{2} = 0.89); 2017, y = 8.22x − 2.29 (R^{2} = 0.95); 2018, y = 5.04x − 0.14 (R^{2} = 0.65). (**E**): 2016, y = 16.07x − 4.38 (R^{2} = 0.92); 2017, y = 11.20x − 2.93 (R^{2} = 0.95); 2018, y = 6.59x − 0.39 (R^{2} = 0.62). (**F**): 2016, y = 13.93x − 4.07 (R^{2} = 0.91); 2017, y = 9.38x − 2.53 (R^{2} = 0.95); 2018, y = 5.63x − 0.23 (R^{2} = 0.62). (**G**): 2016, y = 0.70x − 0.05 (R^{2} = 0.44); 2017, y = 0.66x − 0.31 (R^{2} = 0.93); 2018, y = 0.48x + 0.81 (R^{2} = 0.59). (**H**): 2016, y = 0.62x − 0.03 (R^{2} = 0.48); 2017, y = 0.53x − 0.12 (R^{2} = 0.93); 2018, y = 0.41x + 0.87 (R^{2} = 0.60). (**I**): 2016, y = 1.10x − 0.52 (R^{2} = 0.91); 2017, y = 0.75x − 0.12 (R^{2} = 0.96); 2018, y = 0.72x + 0.66 (R^{2} = 0.71). (**L**): 2016, y = 0.90x − 0.38 (R^{2} = 0.90); 2017, y = 0.59x + 0.05 (R^{2} = 0.95); 2018, y = 0.59x + 0.76 (R^{2} = 0.71). (**M**): 2016, y = 0.31x − 1.06 (R^{2} = 0.87); 2017, y = 0.27x − 1.03 (R^{2} = 0.94); 2018, y = 0.11x + 1.18 (R^{2} = 0.61). (**N**): 2016, y = 0.27x − 1.35 (R^{2} = 0.86); 2017, y = 0.21x − 0.98 (R^{2} = 0.94); 2018, y = 0.09x + 1.07 (R^{2} = 0.61).

**Table 1.**
Leaf nutrition assessment for main macro and micro-elements performed on leaf blades sampled each at veraison from different node positions along the main stem (basal, median, and apical).

**Table 1.**
Leaf nutrition assessment for main macro and micro-elements performed on leaf blades sampled each at veraison from different node positions along the main stem (basal, median, and apical).

| N (%) | P (%) | K (%) | Ca (%) | Mg (%) | S (%) | Na (ppm) | Fe (ppm) | Mn (ppm) | B (ppm) | Zn (ppm) |
---|

**Treatment (T)** | | | | | | | | | | |

N+ | 2.21a | 0.34b | 0.64 | 2.89 | 0.66 | 0.21 | 73 | 102 | 59b | 25 | 17b |

N0 | 1.60b | 0.59a | 0.66 | 3.12 | 0.63 | 0.19 | 85 | 94 | 76a | 27 | 20a |

**Position (P)** | | | | | | | | | | |

Basal | 1.75c | 0.42b | 0.69 | 2.69b | 0.53b | 0.18b | 83 | 107 | 79a | 25 | 22a |

Median | 1.94b | 0.49a | 0.64 | 3.19a | 0.68a | 0.19b | 80 | 100 | 67ab | 27 | 17b |

Apical | 2.02a | 0.49a | 0.62 | 3.12a | 0.73a | 0.22a | 74 | 88 | 56b | 26 | 17b |

**Year (Y)** | | | | | | | | | | |

2016 | 2.00a | 0.43b | 0.71a | 2.60b | 0.55b | 0.24a | 58b | 126a | 78a | 29a | 19 |

2017 | 1.80c | 0.47ab | 0.54b | 3.29a | 0.69a | 0.19b | 66b | 72c | 68ab | 29a | 18 |

2018 | 1.92b | 0.49a | 0.70a | 3.12a | 0.69a | 0.18b | 112a | 97b | 57b | 20b | 18 |

T | ** | ** | ns | ns | ns | ns | ns | ns | * | Ns | * |

P | ** | * | ns | * | * | * | ns | ns | * | Ns | * |

Y | ** | * | ** | ** | * | ** | ** | ** | * | ** | ns |

T × P | ** | ns | ns | ns | ns | ns | ns | ns | ns | Ns | ns |

T × Y | * | ** | ns | ns | ns | ns | ns | ns | ns | Ns | ns |

P × Y | Ns | ns | ns | ns | ns | ns | ns | ns | ns | Ns | ns |

**Table 2.**
Vegetative growth, yield components, and Ravaz Index (vine yield to-total pruning weight) recorded over 2016, 2017, and 2018 for nitrogen (N)+ and N0 treatment levels.

**Table 2.**
Vegetative growth, yield components, and Ravaz Index (vine yield to-total pruning weight) recorded over 2016, 2017, and 2018 for nitrogen (N)+ and N0 treatment levels.

| Main Pruning Weight (g/vine) | Lateral Pruning Weight (g/vine) | Total Pruning Weight (g/vine) | Yield (g/vite) | Cluster Weight (g) | Berry Weight (g) | Cluster Compactness (g/cm) | Shot Berries (%) | Live Green Ovaries (%) | Ravaz Index (kg/kg) |
---|

**Treatment (T)** | | | | | | | | | |

N+ | 200.4a | 66.2a | 266.67a | 651a | 155a | 2.08a | 19. 10 a | 8.44b | 0.99a | 2.80a |

N0 | 169.7b | 26.8b | 196.50b | 291b | 72b | 1.64b | 9.76b | 22.72a | 0.27b | 1.55b |

**Year (Y)** | | | | | | | | | |

2016 | 187.1ab | 53.7a | 240.87a | 529b | 137a | 2.13a | 17.59a | 26.22a | 1.24a | 2.19b |

2017 | 166.2b | 39.7b | 206.00b | 706a | 139a | 1.99a | 17.96a | 4.58c | 0.48b | 3.54a |

2018 | 201.8a | 46.1ab | 247.87a | 178c | 65b | 1.46b | 7.73b | 15.94b | 0.15b | 0.80c |

T | ** | ** | ** | ** | ** | ** | ** | ** | * | ** |

Y | * | * | * | ** | ** | ** | ** | ** | ** | ** |

T × Y | * | ** | ** | ** | * | ns | Ns | ns | Ns | ** |

**Table 3.**
Absolute and relative growth of the three main berry organs/skin, flesh, and seeds) recorded over 2016, 2017, and 2018 for N+ and N0 treatment levels.

**Table 3.**
Absolute and relative growth of the three main berry organs/skin, flesh, and seeds) recorded over 2016, 2017, and 2018 for N+ and N0 treatment levels.

| Skin Weight (g/berry) | Flesh Weight (g/berry) | Total Seed Weight (g/berry) | Mean Seed Weight (mg) | Seed Number (n/berry) | Skin-to-berry Ratio (%) | Seed-to-berry Ratio (%) | Flesh-to-berry Ratio (%) | Skin-to-flesh Ratio (%) |
---|

**Treatment (T)** | | | | | | | | |

N+ | 0.152 | 1.960a | 0.092a | 36.79a | 2.49a | 7.39b | 4.22a | 88.39a | 8.48b |

N0 | 0.141 | 1.515b | 0.066b | 32.77b | 2.00b | 8.97a | 3.83b | 87.28b | 10.42a |

**Year (Y)** | | | | | | | | |

2016 | 0.138b | 2.012a | 0.080b | 32.52b | 2.54a | 6.38c | 3.52b | 90.09a | 7.12b |

2017 | 0.156a | 1.703b | 0.090a | 38.18a | 2.29ab | 8.48b | 4.31a | 87.22b | 9.85a |

2018 | 0.143b | 1.375c | 0.066b | 33.64b | 1.92b | 9.68a | 4.25a | 86.19b | 11.39a |

T | ns | ** | ** | ** | ** | ** | * | * | ** |

Y | * | ** | ** | ** | ** | ** | ** | ** | ** |

T × Y | ** | ** | ** | Ns | ** | ns | ns | ns | ns |

**Table 4.**
Grape composition determined at harvest on musts obtained from vines that, over three years (2016, 2017, and 2018) were subject to N supply (N+) or received no N supply (N0).

**Table 4.**
Grape composition determined at harvest on musts obtained from vines that, over three years (2016, 2017, and 2018) were subject to N supply (N+) or received no N supply (N0).

| Total Soluble Solids (Brix) | pH | Titratable Acidity (g/L) | Tartrate (g/L) | Malate (g/L) | Total Anthocyanins (mg/g) | Total Phenols (mg/g) |
---|

**Treatment (T)** | | | | | | | |

N+ | 23.6b | 3.42 | 11.82a | 7.57b | 5.89a | 0.584b | 1.865b |

N0 | 25.8a | 3.39 | 7.70b | 8.58a | 2.65b | 1.047a | 2.939a |

**Year (Y)** | | | | | | | |

2016 | 25.1 | 3.36 | 8.15c | 8.57a | 3.65c | 1.083a | 2.750a |

2017 | 23.7 | 3.43 | 9.55b | 9.27a | 4.35b | 0.667b | 1.703b |

2018 | 25.2 | 3.42 | 11.58a | 6.40b | 4.81a | 0.697b | 2.754a |

T | ** | ns | ** | * | ** | ** | ** |

Y | * | ns | ** | ** | ** | ** | ** |

T × Y | ** | ns | Ns | ** | ** | ** | ns |