Effect of varying levels of potassium on berry quality of Cabernet Sauvignon grapes under tropical conditions

Abstract

Potassium, an essential nutrient for grapevine has profound effect on berry growth and development and subsequently on wine quality. A sharp increase in berry potassium levels is observed due to potassium redistribution from leaves to berries after veraison. But excessive levels of potassium in berries at harvest may reduce the quality of must and have a negative impact on wine quality, particularly in red wines. Potassium has been implicated in reduction in tartaric acid in juice with overall increase in the pH of wine. To standardize potassium requirement of Cabernet Sauvignon on 110R rootstock in relation to quality parameters of berries, present investigation was carried out during 2014-15 at ICAR-NRC for Grapes, Pune. The experiment was laid out as per RBD having five graded doses of potassium as sulphate of potash viz. 0, 50, 100, 500, 600 kg K2O/ha per year. Each treatment was replicated 4 times. Except control, more fructose content in berries were observed in comparison to glucose in all potassium treated vines. Potassium applications resulted in decreased tartaric and malic acid content in berries. More caftaric acid (53.3 ppm), chlorogenic acid (86.7 ppm), epicatechin (34.7 ppm) and quercetin hydrate (251 ppm) content was recorded in vines treated with 100 kg of potassium per hectare. Increasing trend in petiole content of K, Ca, Na and Cu was found. Juice acidity and pH increased with increasing potassium application.