Effects of soil pH on growth, early fruiting and mineral nutrient profile of ‘Honeycrisp’ apple trees grafted on eight rootstocks

• Soil pH levels and rootstock genotype affect nutrient profile of ‘Honeycrisp’ apple trees. • Fruit size, bitter pit, soluble solids are all affected by pH and rootstocks. • Soil pH and rootstock choice can have large economic impact on orchard productivity. Soil pH affects apple tree growth and fruit quality due to its effects on nutrient uptake. In this study, eight apple rootstocks (Geneva® G.11, G.41, G.935, G.202, G.214, Malling (M) M.9T337, M.26EMLA, and Budagovsky (B.9) grafted with ‘Honeycrisp’ apple cultivar were grown in 55 L pots with the soil pH adjusted to 5.0, 6.5 and 8.0. at Ithaca NY for two growing seasons from 2017 to 2018. Soil pH had a significant effect on tree growth with the best growth at the highest pH. Soil pH affected fruit peel nutrient concentrations of P, Ca, Mg, Fe, S, B, and Zn. Leaf nutrients concentrations were also affected by soil pH with low pH resulting in higher values of K, Ca, Mg, S, Fe and Mn and higher soil pH resulting in higher values for P and Zn. Fruit quality indices including total soluble solids, fruit's firmness and bitter-pit incidence measured after 5 months of storage were unaffected by soil pH. However, greater fruit size was found at higher pH. Among rootstocks, G.935 had the greatest TCSA increase whereas B.9 had the smallest TCSA increase. The highest fruit number per tree in the second season was with G.41 and the lowest bitter pit % was with G.935. G.11 had the largest fruit size while G.935 had the best fruit red skin color. There were no significant interactions between rootstock genotype and soil pH on tree growth but there were several significant interactions of soil pH and rootstock genotype on leaf mineral concentrations and fruit quality.