EFFECT OF SEAWEED EXTRACTS-BASED LEAF SPRAYS ON THE MINERAL STATUS, YIELD AND FRUIT QUALITY OF APPLE

Colour intensity and distribution are essential commercial parameters for red apple cultivars, especially when grown in areas with restricted temperature range. In order to improve these quality parameter several treatments have been tested in the past (i.e. potassium fertilization). The present study reports data collected over two years (1999-2000) from a drip irrigated high density apple orchard (cv. Mondial Gala and Fuji on M9) planted in January 1997 on a loamy soil in the Po Valley (Northern Italy). Fourty trees for each cultivar were subjected to the application of seaweed extracts-based (brown algae, Fucus spp) leaf sprays (by a commercial product) including mineral nutrients at the rate of 3.8, 3.5, 5.9 kg ha^-1 year^-1 of N, P₂O₅, K₂O, respectively. Sprays were applied 8 times per year, at fortnightly intervals from April to September. Treated and control trees received a traditional fertilization with granular and surface applied fertilizers (80, 57 and 120 kg ha^-1 year^-1 of N, P₂O₅, K₂O). Foliar sprays improved red colour intensity and distribution in cultivar Mondial Gala but not in Fuji. Foliar sprays did not affect yield, fruit weight, vegetative growth and mineral composition of leaves and fruits in either cultivars.