Macro and micro element requirements of young and bearing apple trees under drip fertigation

‘Brookfield Gala’ apple trees on Merton 793 rootstock were planted on a loam sand soil at 2000 trees ha−1, trained to a central leader using the solaxe system and supplied with nutrients by drip fertigation. Trees were individually excavated at successive phenological stages in growth seasons two and three, and divided into structural components which were dried, weighed, and analysed to determine their macro and micro nutrient element concentrations. Losses in fruit, leaf drop and pruning were calculated, as were transfers to the permanent structure (fixation). To offset losses and fixation, second season trees needed to take up N, P, K, Ca, Mg and S at 34.5, 3.7, 23.8, 23.9, 5.8 and 1.8 g tree−1, respectively. Respective requirements for Mn, Fe, Cu, Zn, B and Mo were 118, 541, 18.1, 92.8, 79.4 and 2.1 mg tree−1. For third season trees producing 45.2 t ha−1, mineral requirements were within the ranges: N, 1.7–2.6; P, 0.3–0.4; K, 2.3–3.3; Ca, 0.5–1.9; Mg, 0.2–0.4; S, 0.2–0.2; Mn, 1.3–7.9; Fe, 28.7–32.6; Cu, 0.9–1.1; Zn, 3.0–5.5; B, 5.7–7.6 and Mo, 0.3–0.3 mg kg−1 yield.