Leaf blade and petiole analysis for nutrient diagnosis in Vitis viniferaL. cv. Garnacha tinta

[Backgrounds and Aims] Leaf blade and petiole of the grapevine at different sampling times are normally employed for nutritional diagnosis. Both tissues were studied to determine their reliability for diagnosis at different stages of development and, also, the period of time, around the phenological stage of a reference, in which an analysis could be compared with this reference.[Methods and Results] Blades and petioles of Garnacha tinta grapevine were collected throughout the growing season for analysis of ten essential elements. In general, petioles showed greater variability between replicates for nitrogen, phosphorus, potassium, manganese and zinc, while iron, copper and boron presented greater variability in blades. Differences between consecutive sampling times suggested that references for complete cap-fall will be valid only until fruitset. Furthermore, petiole references at any time within veraison are valid at least until the beginning of ripening, while blade references for veraison are valid from the end of berry development until the advanced ripening stage for most nutrients.[Conclusions] Diagnosis of nitrogen, phosphorus, potassium, manganese and zinc is preferable in the blade at complete cap-fall, fruitset and veraison, while the petiole is a better choice for iron and boron at both complete cap-fall and fruitset, and for boron at veraison. Calcium and magnesium at flowering or veraison, and iron at veraison, showed similar reliability for both tissues. Significance of the Study: This study contributes to identification of improved sampling strategies that improve the accuracy of grapevine nutrient diagnosis based on tissue analysis. © 2013 Australian Society of Viticulture and Oenology Inc.This study was supported by the National Institute of Agricultural Research (Spain), and by the Regional Government of La Rioja (Spain). Projects SC00-016, PR-01-03, PR-01-04, PR-03-05 and PR-04-06.Peer Reviewe