Nitrogen and calcium nutrition and fruit quality of commercial apple cultivars grown in Finland
1998
Dris, R. | Niskanen, R. | Fallahi, E.
During 1994-1995, field experiments were conducted in six apple orchards located in the southwest of Finland (the mainland and the Aland Islands). The cultivars were 'Melba', 'Raike', 'Red Atlas', 'Lobo', 'Aroma', and 'Akero'. Fruit samples were picked at about one week before commercial maturity and stored for three to six months at 2 to 4 degrees C and 85-95% relative humidity. During storage the percentage of physiological disorders was visually recorded. Fruit nitrogen (N) and calcium (Ca), firmness, diameter, juice titratable acidity (TA), and soluble solids concentrations (SSC) were determined at harvest. Nitrogen and Ca in the soil and leaves collected during fruit development were determined. The ranges in fruit N were 296-624 and Ca 27-68 mg kg-1 fresh weight, and in the leaves N 15-23 and Ca 9-19 g kg-1 dry matter. The N/Ca ratio was 5 and 16 and 0.9 and 2.3 in fruit and leaves, respectively. There was more variation between years in N and Ca contents of leaves than that of fruit. Other fruit quality characteristics varied between seasons and cultivars. Leaf N correlated positively with fruit diameter and negatively with fruit dry matter. The incidence of physiological disorders on apples after three month storage was 2 to 13% and after six months 10 to 95%. Fruit with Ca content below 45 mg kg-1 fresh weight were susceptible to bitter pit ('Aroma' and 'Akero') and Jonathan spot ('Red Atlas'). The cultivar 'Melba' was susceptible to bruising damages and 'Raike' and 'Red Atlas' were affected more with internal breakdown and core browning.
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