Potassium in grapes II -: analysis of petioles and their correlation with the potassium content of wine grapes

Grapes from three Vitis vinifera varieties (Pinot Noir, Cabernet Sauvignon and Merlot) were analyzed over a two-year period to determine their potassium content, aiming to monitor this mineral content during the ripening process and evaluate its influence on pH values. Grape samples were harvested periodically during the berries' development until their harvest. As expected, the grapes' potassium content showed variations, i.e., high potassium content went hand-in-hand with increased pH values while low potassium content led to stabilized pH; this process was also affected by the decline in total acidity This finding confirms that high pH values, low titrable acidity and potassium are correlated. In addition, the analysis of petiole samples (collected during inflorescence and 30 days later) proved to be an efficient tool not only for monitoring the potassium content in winegrapes but also for evaluating the need for soil amendments involving this mineral. The potassium content in petioles and in winegrapes was found to be directly correlated; therefore, this method may be useful in future diagnoses of the potassium content in grapes and wines.