EFFECT OF ORCHARD FACTORS AND MINERAL NUTRITION ON BITTER PIT IN ‘GOLDEN DELICIOUS’ APPLES

Abstract

The present five years of research is focused on the effects of field (orchard) and management factors in bitter pit incidence under standard, commercial management. Research was carried out in 20 commercial orchards in 1994, 50 in 1995 and 67 in 1996 in Lleida region (north-eastern part of Spain). There are 42.000 ha orchards in that area, with 10.000 ha of 'Golden Delicious' apples. The relationships between soil fertility, leaf and fruit mineral content, yield, fertilisation, irrigation, cultural practices and orchard factors (rootstocks, tree age, soil management, training, chemical sprays, growth regulators, etc.) and bitter pit incidence have been studied. Incidence of bitter pit was evaluated on three 15-18 kg fruit samples collected from each orchard, stored either for 20 days at room temperature or for 6 months and 9 months in a cold storage. Preliminary results show that bitter pit was usually correlated with Ca content and with K:Ca, (K+Mg):Ca and N:Ca ratios, both in fruits and leaves. Shoot growth and yield were also correlated with incidence of bitter pit. The available preliminary results show that improved management of irrigation, K fertilisation and soil fertility could reduce the incidence of bitter pit.