Rootstock age affects growth and nutrient uptake from apple trees in the nursery

The objective of this study was to evaluate the effect of the rootstock age (one and two years) on the vegetative growth and nutrient uptake from apple trees (cv. ‘Galaxy’ on ‘M.9’ EMLA rootstock). The study was conducted in a commercial nursery in central valley Chile, at a density of 40,000 trees ha^–1. Biomass and nutrient concentrations (N, P, K, Ca, Mg, Mn, Cu, Zn and B) were determined at the end of the growing season, in separate samples of leaves, shoots (wood above the root collar) and roots. The results showed that rootstock age had a significant effect on biomass accumulation and thus on plant nutrient extraction. Apple trees with two-year-old rootstock reached twice the total fresh biomass compared to one-year-old rootstock. Dry biomass was distributed as follows: 33% leaves, 57% shoots and 10% roots. The uptake of macroelements from apple trees with two-year-old rootstock was twice as high as that of one-year-old trees, according to the following descending order: N>Ca>K>Mg>P. Apple trees on two-year-old rootstock took up 3.3 times more Zn, twice more Mn and Cu, and 1.7 times more B compared to those on one-year-old rootstock, with Zn and B as the main elements in the shoots. Differences in the concentration of certain mineral elements were significant at shoot and root level according to rootstock age, being directly related to plant biomass.