Rootstock Interaction with Cultural Practices

This project continues to investigate the interactions of rootstocks with cultural decisions of pruning severity, and between-row or in-row spacing. The project was comprised of several experiments bearing on the interaction of rootstock with cultural practices. In combination with three between row spacings (6, 9, and 12 ft.), nine rootstocks (AxR#l, 110R, 039-16, 5C, 3309, 5BB, 1202, 1616, and 420A) grafted to Chardonnay were evaluated for effects on fruit composition, vine growth, and crop yield in a replicated field plot established at the Beringer’s Hudson Vineyard in Napa, CA. The stocks could be divided into four vigor groups based on the amount of shoot growth as measured by shoot length or lateral and primary leaf areas. 039-16 and 420 A were in classes by themselves as the highest and lowest vigor stocks, respectively. Between the two extremes, 110R, 1202, 5-C, AxR#l, and 1202 exhibited intermediate growth while 3309 and 1616 tended toward low vigor. In general vigor tended to be lower in stocks with V. riparia heritage. Crop loads per vine increased with wider spacing from 8.1 kg/vine at 6 ft to 9.7 kg/vine at 12 ft. The increase was due to larger clusters with more berries per cluster. When considered on a per acre basis, however, yield was 50%higher on the narrow spacing due to more vines per acre. The average yield per acre of the 6, 9, and 12 ft spacings were 9.2, 6.7, and 5.5 tons/acre, respectively. At Oakville, the interaction of rootstock and balanced pruning formula on Cabernet Sauvignon (Clone UCD #8) grapevines was examined for the second year. Results in the second year of study differed substantially from those of 1995. Fruit maturity was not significantly lower on 039-16 as in previous years. Soluble solids increased as crop load decreased whether due to pruning formula of rootstock. Crop yield was reduced on 039-16 relative to the other stocks due to lower clusters per shoot and by pruning formula through reduced shoot number. Yields were 5.6 kg/vine for 039-16 and an average of 8.1 for 110R, 3309, and 5-C. The 5, 7, 9, and 11 bud/lb treatments produced yields of 5.5, 7.1, 7.6, and 8.6 kg/vine, respectively. No other components of yield (berry weight, cluster weight and berries per cluster) were found to be compensating for cluster number. Please consult the complete Final Report for other results and remaining experiments.