Impact of Vine Vigor, Nitrogen, and Carbohydrate Status on Fruitfulness of Pinot Noir

The first year of a two-year research project was completed in 2014. The project involves three components, all analyzed within main plot vines managed with different vineyard floor management practices and different levels of vine vigor and nitrogen status. Preliminary results show that bud fruitfulness is not reduced at basal nodes for canes assessed within any of the vineyard floor treatments. Vines grown with cultivated alleyways (Tilled) were the most vigorous with the greatest leaf area and lowest light infiltration compared to vines with grass alleyways (Grass). Dormant buds collected in winter 2014 from Tilled treatment vines had the highest fruitfulness at several nodes along the cane. Primary bud necrosis was rarely found and did not differ between Tilled and Grass treatments. Grass vines had less leaf area, lower yields and higher fruit total soluble solids at harvest as was found in prior years of research in this block. Vine tissue N and carbohydrate analysis are still pending as of this reporting. The differences in nitrogen (%N) and total non-structural carbohydrates of bud, cane, shoot, trunk and root samples will be compared to bud fruitfulness data to understand the dynamic role of N and carbohydrates on bud development and fruitfulness. Within the main plot vineyard floor management study, two experiments were conducted within sub-plots to evaluate the effect of canopy management practices on bud fruitfulness, including lateral removal and cluster zone leaf removal. Both included a time course study of lateral and leaf removal.

Lateral shoot removal treatments were imposed during one of three different time points (fruit set, pea-size and bunch closure) in 2014 and compared to a no lateral removal treatment. Timing of lateral removal did not increase light exposure to the upper canopy where laterals were removed, indicating that any differences in bud fruitfulness within apical sections of dormant canes may be due to internal differences such as nitrogen or carbohydrates rather than light or temperature effects. The main differences in canopy light were due to the main plot effect (Grass, Alternate and Tilled). There were no differences in photoassimilation rates of primary leaves with or without a lateral. Data collected from these experiments will be compared with bud fruitfulness that is currently being assessed for winter 2015. Cluster zone leaf removal was applied to vines during one of three different time points during 2014 (bloom, fruit set, and pea-size), and these were compared to a no leaf removal treatment. Leaf removal increased light exposure to the buds in the fruit zone where leaves were pulled. Within the Grass vines, yields were higher with no leaf removal compared to those with leaf removal. Grass vines had lower total vine leaf area than Alternate and Tilled vines, and removal of leaves early season could have affected fruit set. Fruit set data are still being analyzed. Data collected from these experiments will be compared with bud fruitfulness that is currently being assessed for winter 2015.