Rootstock Interactions with Cultural Practices
This project covers three objectives. It evaluates the interaction of rootstock with increased buds retained at pruning at the Oakville Experimental Vineyard, the performance of rootstocks with several in-row spacings under non-irrigated conditions at the Oakville Experimental Vineyard and the interaction of nine rootstocks with potassium application in Merlot with Chalk Hill Vineyards.
The response of cordon trained Cabernet Sauvignon on 110R, 101-14, and 5-C rootstocks to a wide range of pruning levels was evaluated to examine the interaction of rootstock and pruning formula. Rootstock had no effect on the measured components of fruit composition at harvest. Maturities varied in response to pruning level with a significant interaction between pruning and spacing. Closer spacing resulted in a steeper decline in maturity with incremental increases in bud number. This was especially evident for vines planted on 5C. Pruning level influenced components of yield that depend on shoot number: clusters per vine and total yield. It had no independent effect on components that depend on bud fruitfulness: clusters per shoot and cluster size. Significant interactions arose between pruning and rootstock on the number of berries per cluster and final cluster weight. Cluster weights tended to increase with increasing pruning levels on 5-C and decrease with increasing pruning levels on 110R. Berry size was reduced at high bud numbers on 101-14 and 110R.
In 2000, the in-row spacing treatments had yields of 3.22, 4.07 and 4.44 kg m-1, for the 1.0, 1.6 and 2.2 meter spacing, respectively. The differences in yield was attributed to the numbers of berries per cluster with the 1.0, 1.6 and 2.2 m treatments having 120, 130 and 133 berries cluster-1, respectively. There were no differences in berry weight. The four-year average also showed that yield was lower at the 1.0 m spacing than the 1.6 and 2.2 m spacing treatments, 2.49, 3.15 and 3.20 kg m-1, respectively. The lower yield of the 1.0 m spacing was attributed to both smaller berries and fewer berries per cluster. In 2000, there was no effect of rootstock on yield for those vines pruned to equivalent buds per vine. Likewise, the components of yield, berry weight, cluster weight and berries per cluster did not differ. These results are consistent with the cumulative four-year averages.
At the Chalk Hill Merlot site yield in 2000 was equal to the four-year mean at 8.5 kg vine-1. However, when the effect of the potassium fertilizer treatment is taken into account we see a different picture. Yields for vines receiving potassium fertilizer were slightly higher (0.4 kg vine-1). Indeed, yield has been higher for vines receiving potassium fertilizer for all but the first year. In the last two years, 1999 and 2000, the increased yield has been approximately 1.5 kg vine-1. The yield increase has been largely accomplished through an increase in cluster number arising from an increase in shoot number. The vines have been pruned as was appropriate for each vine therefore, the increase in shoot number represents an increase in perceived capacity.