Effect of Media pH on Growth and Leaf Tissue Element Concentration of ‘Vidal blanc’ and ‘Norton’ Grape Cultivars

Abstract

The study involved two grape cultivars (‘Vidal blanc’ and ‘Norton’), grown in pots with media amended to pH 4.5, 5.9, 7.2, or 8.5. The objectives were to determine vegetative growth and mineral element concentration of these cultivars as affected by media pH and to determine the optimum pH range within those tested for cultivar growth. ‘Vidal blanc’ was superior to ‘Norton’ in all growth measurements. Raising media pH from 5.9 to ≥7.2 led to significant reductions in shoot length, specific leaf weight, leaf and shoot dry weight, and an increase in root to shoot ratio for ‘Norton’, but not for ‘Vidal blanc’. For ‘Norton’, a comparatively higher reduction in shoot versus root growth was responsible for increased root to shoot ratio above ≥7.2. Except for low P concentration in ‘Norton’ at media pH 8.5 and high Mg concentration in ‘Vidal blanc’ at media pH 5.9, other macronutrient concentrations did not differ with media pH or cultivars. Despite having a similar or even higher Fe concentration than ‘Vidal blanc’, ‘Norton’ showed noticeable Fe deficiency symptoms at media pH above 5.9. At harvest, plants at media pH 4.5 had 10–20 times more Mn and 3–8 times more Al than plants grown at alternative media pH levels. Media pH range 5.9 to 7.2 and 7.2 to 8.5 appears to encompass the optimum pH for growth of ‘Norton’ and ‘Vidal blanc’, respectively.