Shoot Density Effects on Riesling Grapevines: Interactions with Cordon Age

Abstract

An experiment in the Similkameen Valley near Cawston, B.C. examined the impact of three shoot densities (20, 30, and 40 shoots/m of row) in combination with three cordon ages (year of establishment: 1983, 1986, and 1987) on Riesling vine performance, fruit composition, and wine sensory attributes. No effect of either factor was observed on weight of cane prunings. Periderm formation was inhibited by increased shoot density. Yield, clusters per vine, and crop load increased with increasing shoot density, but cluster weight, berries per cluster, and berry weight displayed concomitant decreases. Old cordons (1983) were associated with higher yields and high cluster weights. Effects on fruit composition were minor, and tended to be associated with cordon age more than shoot density; for example, highest titratable acidity, free volatile terpenes, and potentially volatile terpenes were found in berries and juices from 1983 cordons. Canopy density, leaf layer number, and shaded clusters and leaves increased linearly with increasing shoot density, but cordon age appeared to have no effect. Tasters found most fruity aroma and flavor, as well as the least grassy aroma and flavor, in treatments from lowest shoot densities and oldest cordons. Principal components analysis showed that wines from old cordons were best explained by fruity and candy (aroma and flavor) as well as sweetness descriptors, while wines from 1986 cordons and the 1987 cordon x 40 shoots/m combination were best explained by grassy aroma and flavor. Existing shoot density recommendations were confirmed by these data.