The influence of site aspect and pruning types on Pinot Noir phenology and shoot growth

Aim: Managing the influence that terroir in vineyards has on vine development depends on improving our understanding the effect of the interaction of within-site variability, within-vine variability, and management practices (such as pruning types) on phenology and vine development. This study evaluates the consequence of site aspect and pruning management on budburst, leaf appearance rate, and shoot growth in Pinot noir vines.

Methods and Results: Two rows of 19-year-old Pinot noir vines were selected within a commercial vineyard with south, hilltop, and north-facing aspects (note: the north-facing slope is sun-facing in the Southern Hemisphere). Vines were either cane- or spur-pruned, retaining 20 nodes per vine. Budburst, shoot development, and leaf appearance were assessed, and vine trunk circumference was measured to quantify the accumulated differences in vine vigour.

Hilltop plots had smaller trunk circumferences when compared to the south- and north-facing plots. Irrespective of topographical positions, budburst was earlier in cane-pruned vines compared to spur-pruned vines, but no differences were observed by the time of 12-leaf stage. The rate of shoot growth reflected the variations in topographical positions and trunk circumference. Cane-pruning exhibited more significant within-vine variation in budburst, budburst duration, and shoot growth when compared with spur-pruning. Shoots from hilltop vines were shorter relative to the vines at other plots for both pruning systems.

Conclusions:

The rate of shoot growth and development was associated more with site and vine vigour as determined by trunk circumference than pruning type. Spur-pruned vines had a later but more uniform budburst when compared to cane-pruned vines.

Significance and Impact of the Study: Pruning type and within-site variability may lead to differences in canopy density and vine vigour, which can ultimately impact subsequent growth and development of the grapevine. Determining the influence of terroir within the vineyard on budburst, leaf appearance, and shoot growth variability will enable the development of improved phenology and growth models to describe within vineyard variability.