Novel Critical Levels and Nutrient Content Ranges in Leaf Tissue for Prominent Grapevine Cultivars in California and Oregon

Background and aims: The study aimed to evaluate the nutritional similarity among grapevine cultivars across different counties and to propose nutritional reference values in leaf tissue for prominent cultivars and growing regions. This approach is noteworthy because nutrient management guidelines for vineyards are generally based on tissue analyses that lead to broad interpretations applied uniformly across cultivars and regions, without accounting for cultivar-specific nutritional requirements or differences in edaphoclimatic conditions among counties. Methods: The proposed approach was applied to a database comprising 3,256 samples of complete leaves (blade + petiole) collected over multiple years from vineyards of Cabernet Sauvignon, Chardonnay, Merlot, and Pinot Noir. The vineyards were located in five counties in California and Oregon: Lake, Monterey, San Luis Obispo, Polk and Yamhill. Leaf samples (blade + petiole) were prepared and submitted for analysis to determine the N, S, P, K, Ca, Mg, Zn, Cu, Mn, Fe, B and Na concentrations. Results: Leaf nutrient data were analyzed using the Compositional Nutrient Diagnosis (CND) approach, allowing the establishment of cultivar- and region-specific critical levels (CL) and nutrient sufficiency ranges, including upper (UL) and lower (LL) limits. Conclusion: The results confirmed that grapevine nutritional status and nutrient sufficiency ranges vary according to both cultivar and growing region, demonstrating that generalized nutrient standards may not adequately represent grapevine nutritional requirements. The CND-derived CL, UL, and LL values provide a more accurate basis for nutritional diagnosis, supporting site-specific fertilizer recommendations, improving nutrient-use efficiency, and contributing to sustainable vineyard management. The proposed approach also provides a framework that can be adapted to other viticultural regions where regionalized nutrient reference values are still unavailable.