Spritzungen mit Calciumchlorid erhöhen die Calcium- und reduzieren die Kaliumkonzentrationen der peripheren Schichten von Apfelfrüchten

Eight year old apple spindle trees (‘Elstar’, ‘Gala’, ‘Karmijn de Sonnaville’, ‘Pinova’, ‘Pilot’) were sprayed 12 times with aqueous CaCl₂ (400?l/ha) from July through September 2004. Controls (Fu) were trees sprayed with fungicides only (Captan 80, Dithane Ultra, Euparen M and Malvin). The treatment (FuCa) was sprayed with fungicides plus CaCl₂ (increasing concentrations from 5 to 25?g/l during the season) and the treatment FuCaTe contained in addition the surfactant Plantacare 1200 UP, which reduced surface tension to 29–30?mN/m. Ca concentration in the first layer (0–5?mm) of the control fruits (Fu) ranged from 7.6 (‘Elstar’) to 9.8?mg/100?g fresh weight (‘Pilot’). Ca concentrations in the second layer (5–10?mm) were lower and ranged from 4.5 (‘Pinova’) to 6.2?mg/100?g (‘Karmijn de Sonnaville’). CaCl₂ applications to fruits (FuCa) increased Ca concentrations in the first layer to 12.7 (‘Elstar’) or 14.2?mg/100?g (‘Pinova’ and ‘Pilot’). Ca concentrations in the second layer were also increased by the treatments. They ranged from 5.4 (‘Karmijn de Sonnaville’) to 9.1?mg/100?g (‘Pinova’). Adding the surfactant (FuCaTe) further increased Ca concentrations (‘Pilot’) up to 17.4 and 10.6?mg/100?g in the first and second layers, respectively. This effect of the surfactant was the result of faster penetration into fruits of CaCl₂ which reduced losses by rain shortly after spraying. Potassium concentrations were about 70?mg/100?g in both layers. Treatments with CaCl₂ leading to higher Ca concentrations in the fruits resulted in a decrease in K concentrations to 21 (first layer) or 50?mg/100?g (second layer). It is not clear if this was caused by a reduced K-influx into fruits or by displacement of K from peripheral into deeper layers of the fruits.