Tissue nutrient concentration is useful for determining vine nutritional status and managing vineyard nutrition. Current Australian guidelines are based on the analysis of petioles at flowering and leaf blades at veraison, sampled adjacent to the basal inflorescence and bunch. The comparative value of these two tissue types and that of the bunchstem for assessing plant nutrient status at the two phenological stages is required. Moreover, the impact of node position and cultivar is unclear.Methods and Results
We characterised the macro and micronutrients at flowering and veraison of three segments of the petiole, the entire leaf blade and the bunchstem at two node positions of cvs Cabernet Sauvignon, Shiraz and Chardonnay grown under identical conditions. Nutrient concentration was non-uniform along the length of the petiole. The middle segment had the lowest concentration of most macronutrients, while Mn was generally highest in the middle segment. When averaged across petioles, blades and bunchstems the lower node had a higher nutrient concentration than the upper node, except for K. The concentration of some nutrients within the leaf blade was correlated with those of the petiole but this was dependent on the cultivar and the time of sampling. The nutrient concentration of the bunchstem was more closely correlated to the petiole than to the blade. Cultivar differences were also apparent, but this depended on the individual nutrient and the sampling time.Conclusions
Nutrient concentration was inconsistent along the length of the petiole. The nutrient concentration of petioles, blades and bunchstems was node, cultivar and time specific. Therefore, tissue nutrient analysis will be meaningful only if sampling is consistent across these variables.Significance of the Study
These results will aid in the formation of better sampling protocols for accurate grapevine nutrient diagnosis.