Three potential variables, shoot basal diameter, leaf count per shoot, and shoot length, were examined as potential rapid, nondestructive methods for estimating leaf area per shoot, a frequent component of estimates of leaf area per vine. The metrics were recorded in large field-grown vines over five years. Shoot basal diameter, the most rapid method, was not a good predictor of leaf area per shoot. After transformation, shoot length and leaf count per shoot had relatively tight linear relationships with the square root of leaf area per shoot (R2 = 0.90 and R2 = 0.85, respectively). Some of the variation in the relationships due to between-year and within-season variability can be reduced by expressing the relationships as a function of thermal time. Furthermore, nonlinear models can be fit to the ratio of leaf area per shoot to the rapidly obtained metrics. Using this ratio approach accounts for the dynamics of canopy development and should increase the accuracy of leaf area estimates during early-season rapid shoot growth. Early in the season the length and count measurements can be made at ~0.5 min per shoot, but as the canopy develops and shoots intertwine, the sampling rate progressively slows to ~2.5 min per shoot.
- Copyright © 2007 by the American Society for Enology and Viticulture