Influence of Rootstock on Seasonal Foliar Levels of N and K
Petioles and blades were collected from 4 vineyards at 3 phenological dates (bloom, veraison and harvest). Three of the 4 vineyards had identical lists of 14 rootstocks while the fourth had 9 rootstocks. The 1997 samples were ground and submitted for analysis, with only part of them returned at this time. Seasonal results from 1995 and 1996, averaged for all rootstocks, show different nutrient patterns among the scion varieties. Cabernet Sauvignon K decreased in petioles from bloom through harvest or petioles and blades, except for blades in 1996, which showed a small rise between bloom and veraison. Chardonnay and Zinfandel had equal or slightly higher veraison K levels compared to bloom, but all values decreased by harvest. Nitrate was much higher in petioles than in blades and showed dramatic differences in petiole NO3 between the two years with very high values in 1996. In all cases petiole NO3 levels rose slightly between veraison and harvest. Nitrogen (%total) values were much more similar between years and were higher in blades than in petioles. In both cases, levels of N seemed to decrease throughout the year. Relative differences among rootstocks are more easily seen. While rootstocks generally high or low in N or K at bloom tend to remain that way throughout the entire year, this is not always the case. When the 1997 data is available, correlation analysis will be done in order to examine the effect of tissue and season. In addition, rootstocks will be ranked and trends will be established among sites/scions.