Relationships between leaf and fruit minerals and fruit quality attributes of apples grown under northern conditions

Field experiments were conducted during 1994-1995 in seven apple (Malus spp.) orchards located in the southwest of Finland (the mainland and-the Aland Islands). The cultivars were 'Transparente Blanche', 'Samo', 'Melba', 'Raike', 'RedAtlas', 'Akero', 'Aroma', and 'Lobo'. Leaf samples from branches bearing fruits (BF) and not-bearing fruits (BNF) were collected two times during the growing seasons. Fruit samples were picked about one week before commercial maturity. Macronutrient concentrations in fruits and leaves, fruit diameter and juice pH, titratable acidity (TA) and soluble solids concentrations (SSC) were determined. Leaf nitrogen (N), phosphorus (P), and potassium (K) were higher, but calcium (Ca) and magnesium (Mg) were lower:in BNF. Branch types (BF and BNF) were closely related in leaf N, P, and Ca, but not in leaf K and Mg at the first sampling time. Fruit N, P, K, and Mg were closely related to each other but not to fruit Ca. Mean fruit N and Ca and leaf P and Mg were low compared with the recommended levels. Relationships between fruit and leaf nutrient concentrations were found only in P and Mg. Fruit diameter increased and juice SSC decreased with increasing leaf N concentration. Fruit P declined with increasing fruit diameter and juice TA increased and SSC/TA decreased with increasing leaf P and Ca concentrations.