Effects of Media Ph on Growth and Nutrient Content of Two Grape Cultivars

The study involved two grape cultivars, Vidal blanc and Norton, growing in pots with amended media of pH 4.5, 5.9, 7.2, or 8.5. The two factor experiment was set up in a randomized complete block design with six replications. The objectives were to determine vegetative growth and nutrient content 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 and 8.5 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 than root growth was responsible for increased root to shoot ratio above 7.0. Cultivars had similar levels of K, Fe, and Cu, but Norton had higher P, Ca, B, and A1 and lower Mg than Vidal blanc. Increasing media pH led to lower P, Mg, Mn and higher B in both cultivars. Unlike Vidal blanc, Norton showed noticeable Fe, Mn and Mg deficiency symptoms at media pH above 7.0 despite having higher content than Vidal blanc. This most likely indicates poor utilization rather than a deficiency of these nutrients for Norton. The 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