Seasonal variation of macro and micronutrients in blades and petioles of Vitis vinifera L. cv. Mencía and Sousón

In the case of grapevine (Vitis vinifera L.), leaf blade and petioles at different sampling times are used for nutritional diagnosis and planning fertilization practices. However, reference values for each nutrient depend on the scion‐rootstock combination. In this sense, the current study aimed at determining the reliability of leaf blade and petiole for diagnosis at different phenological stages and, also, of the period of validity, around flowering and veraison, in which the nutrient concentrations obtained could be compared with reference values. The study was carried out in three vineyards (two planted with cv. Mencía and one with cv. Sousón) within the Ribeira Sacra Designation of Origin (NW Spain). Blades and petioles were collected throughout a growth season (2014) and total concentrations of ten essential elements were determined in both tissues. In general, petioles showed greater variability between replicates for P, K, Ca, Mg, and Zn, while N, Fe, Mn, Cu, and B presented greater variability in blades. Differences between consecutive sampling dates suggest that references for flowering were valid until fruit‐set. Furthermore, blade and petiole references at the beginning of veraison were valid until the advanced ripening stage for most nutrients, with the exception of N, P, and Zn. The seasonal variation of the concentrations in both tissues confirmed the need for reference values for each phenological stage and tissue.