Effect of sampling time on the petiole nutrient composition in grape (Vitis vinifera L.)

In order to standardize leaf-sampling time in Perlette grape, seasonal variation a major factor contributing variation in tissue nutrient contents was studied. A pronounced decline in N, P, K and S concentration was observed with the advancement of the sampling period, while Ca, Mg and Mn increased consistantly throughout the season. Copper and Zn, however, showed irregular trends throughout the season. The nutrients in petioles opposite to clusters were found to be stable during May and June, which appears to be the most suitable time of tissue sampling in Perlette grape.