Effect of Rootstocks on grapevine mineral nutrition in the Central Coast Region

This study is comparing the differences in vine mineral nutrient status as influenced by rootstock in Central Coast wine grapes. Four rootstocks trials have been sampled to date to include Chenin blanc and Chardonnay in Soledad, Chardonnay at York Mountain (Paso Robles), and Cabernet Sauvignon at Santa Ynez. All are irrigated sites, except York Mountain, and compare 7 to 10 rootstocks, depending on location. All of the sites have been sampled at bloom while two of the sites (York Mountain and Santa Ynez) were also sampled at veraison in 1993. Analyses included total N, N03-N, P, K, Ca, Mg, Na, CI, B and Zn. Generally, the results are demonstrating the strong influence that rootstocks can have on scion mineral nutrition. The information should be helpful in anticipating potential nutritional problems, guiding fertilizer recommendations, and selecting rootstocks partly on the basis of nutritional adaptability to the site. The information is preliminary, as additional years of sampling, including fruit analysis, will be needed to determine multi-season responses. However, some preliminary responses are worth noting, especially when they are showing some consistency among sites. They include: 5C = lower N, CI, and Zn; 110R = lower CI and K; 3309 = lower P and Ca but higher CI; 1202 = higher P and Zn; 039-16 and 043-43 = higher N, Na, and CI; Freedom = higher N and K; Harmony = lower N, P, and Ca; St. George = lower CI but higher N and Mg; 5BB and 5A = mostly minor differences. Some of the differences were consistent with the generally good performance of St. George on a dryland site, the relatively poor performance of Harmony in Coastal sites, the general high nutritional status of Freedom, and the potentially high sensitivity of 039-16 to Na and CI problems. Additional information and recommendations should be forthcoming as the study progresses.