Alessandra Garavani

Effects of Early Shoot Trimming of Varying Severity on Single High-Wire Trellised Pinot noir Grapevines

Amid growing concerns over global warming and available management strategies to reduce cluster temperature and prevent overheating and sunburn damage, there is increasing interest in sprawling, nonpositioned canopies as an alternative to traditional vertically positioned ones. However, management of sprawling canopies requires adjustments to maintain a mostly erect growth pattern during the season. A three-year study (2009–2011) was carried out to investigate the performance of 15-year-old Pinot noir grapevines trained to a single high-wire trellis subjected to prebloom shoot trimming to retain seven (T7) or eleven (T11) main stem leaves. There were significant year × treatment interactions: with a low crop and weather conducive to posttrimming lateral regrowth in 2010, trimmed vines had higher leaf area, soluble solids concentration, pH, total anthocyanins, and cluster rot incidence than control vines, whereas in 2009 and 2011, the overall must compositional pattern was reversed due to suboptimal leaf-to-fruit ratios in the trimmed plots. The effects linked to this necessary operation are highly dependent on unpredictable weather occurring after shoot trimming; hence, the milder trimming severity (T11) may more successfully balance the need to induce a still mostly erect canopy while retaining sufficient vine leaves to buffer possible weak lateral formation after trimming. This paper provides new and useful knowledge for improved canopy management in trellises with free shoot growth due to the absence of foliage wires.

Effects of Variable Rate Nitrogen Application on cv. Barbera Performance: Vegetative Growth and Leaf Nutritional Status

Variable rate application of vineyard inputs in field parcels characterized by different levels of vigor and/or yield is one of the most promising applications of precision agriculture. In a four-year study, we provided ground-truthing of three different vigor levels (L = low, M = medium, and H = high) derived pre-trial from Normalized Difference Vegetation Index (NDVI) values determined by remotely sensed imagery (5 m pixel resolution) in a small Barbera vineyard (0.64 ha). Each vigor level was subjected to three fertilization strategies (S) consisting of no N supply (C, 0 kg/ha), standard supply (S, 60 kg/ha), and variable-rate application (VRA) delivering 0, 60, and 120 kg/ha to H, M, and L vines, respectively. Post-trial effects were assessed by taking another NDVI satellite image at the same resolution and by adding proximal sensing performed with the MECS-VINE sensor yielding the estimation of a canopy index (CI). Ground-truthing was based on recording main vine growth parameters and leaf nutritional status. Results show that vine balance of L vines was optimal. Variability among vigor levels was significantly reduced in years 3 and 4, while mean effects related to fertilization strategy were not significant and very few S × V and S × Y interactions were found. However, when the ground-truthing assessment was compared with the CI index values, it was very clear that VRA was able to reduce variability among vigor levels (CV = 1.42%) versus standard fertilization at 60 kg/ha (8.20%).

Mechanical Mid-Shoot Leaf Removal on Ortrugo (Vitis vinifera L.) at Pre- or Mid-Veraison Alters Fruit Growth and Maturation

Production of high-quality sparkling wines relies on an optimal balance between sugar and acidity in the fruit at harvest. Warming trends favor a too-fast sugar increase at the expense of adequate acidity. The removal of photosynthetically active leaves from the distal part of the canopy around veraison has been proposed as a simple technique to delay sugar accumulation. Over three seasons (2015 to 2017), we compared the effects of mechanical mid-shoot leaf removal in the white variety Ortrugo, either performed before veraison (PRE-LR) or at a total soluble solids (TSS) concentration of ~12 Brix (POST-LR), with non-defoliated vines (C). PRE-LR shifted the sugar increase in all the three seasons, but the effects held until harvest only in 2015 and 2016 (−1.1 Brix and −1.4 Brix, respectively, if compared to C). Acidity was unaffected. POST-LR was less effective in changing the composition of grapes during ripening. Both leaf removal treatments reduced berry size (−5%) and yield (−19% PRE-LR and −14% POST-LR, in comparison with C). Finally, the treatments changed the berry morphology and the proportion between its components, with some peculiarities due to the seasons, but the relative skin mass generally increased. Overall, the efficacy of the technique was below expectations, primarily because the delay in general ripening expected from removing a significant portion of the mature and functioning leaves was offset by a decrease in malic acid due to excess heat summation for this variety.