Nutrient Level Comparisons of Leaf Petioles and Blades in Twenty-Six Grape Cultivars Over Three Years (1979 through 1981)

Leaf petiole and blade nutrient levels were compared in 26 raisin, table, and wine grape cultivars at five growth stages over three years, 1979 - 1981. The cultivars are ranked according to total N, NH 4 -N, NO 3 -N, P, K, Zn, and B levels. Total N was highest in blades but did not show wide cultivar differences. NO 3 -N showed wide cultivar differences, especially before and during bloom when levels peaked. These peaks occurred at the same stage in most cultivars each year, suggesting similarities in the influence of seasonal weather patterns on cultivar N metabolism. NH 4 -N analysis may be useful in studying N metabolism differences and problems but showed too many inconsistencies in this study to be of value in estimating N needs. The consistency of cultivars to show high, medium, or low NO 3 -N levels is indicative of their inherent genetic differences in N metabolism. Thus, critical petiole NO 3 -N levels need to be established for individual cultivars. Petiole P levels were generally higher than blade levels among the cultivars, especially at the high range. Petioles and blades approached equal levels at 0.25% P. P levels did not change with time. Cultivars showed wide K level differences among them, especially in the petioles. K levels usually declined between bloom and veraison. Significant year to year differences in K levels also occurred. Zn was usually highest in the petioles and tended to increase with time. Cultivars with a history of Zn deficiency susceptibility ranked low in Zn levels. Cultivar nutrient level differences, relative to one another, tended to be fairly consistent through the season and from year to year. Overall, Black Corinth and Salvador were the highest and lowest ranked cultivars, respectively, in most nutrient comparisons. Other important relationships of plant parts, N compounds, seasonal changes, and yearly differences among the cultivars are discussed.