Canopy microclimate vineyard variability in vineyards of the Lodi region of California, USA

Aim: The aim of this project was to evaluate the microclimatic effects on objective measures of fruit quality within different vigour classes of multiple vineyards and to compare the results across the Lodi region of California, USA.

Methods and Results: In May 2019, small temperature sensors were installed in the fruit zones of 10 vineyards in the Lodi region of California. To assess differences in canopy temperature between high and low vigour areas, three sensors were installed in each vineyard, two in the fruit zone (high and low vigor) and one above the canopy (ambient control). Photosynthetically active radiation in the fruit zone was measured at veraison and harvest on 15 vines surrounding each sensor and compared with the temperature data. At harvest, two randomly selected clusters were collected from each of the 15 data vines, combined into one composite sample per temperature sensor, and analysed for individual objective measures of grape quality. Results showed large differences in fruit composition between vigour zones. Daytime temperatures were higher in low vigour zones and canopy light measurements were correlated with anthocyanins (R² = 0.59), polymeric tannins (R² = 0.55), malic acid (R² = 0.48), and linalool (R² = 0.76).  

Conclusions: 

The results showed large differences in fruit quality within vineyards which implies delivery of heterogenous fruit to wineries. Excessive differences in fruit quality could be ameliorated with appropriate canopy management tools geared towards increasing vineyard uniformity. 

Significance and Impact of the Study: Delivery of reliable fruit to wineries by vineyard managers and consistent wines by winemakers is challenging when harvesting large vineyards into single programs. These risks are highlighted by the above results which also provide further evidence for the need of differential management solutions in wine grape production.