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Abstract
The effects of several rates of KCl (0–1500 kg/ha) were compared with K2SO4 at the equivalent K rate as 1500 kg/ha KCl on five commercial orchards of kiwifruit (Actinidia deliciosa [A. Chev] C.F. Liang et A.R. Ferguson var. deliciosa cv. Hayward). Leaf breakdown (marginal leaf scorch followed by necrosis and leaf drop) was induced by KCl application at four of the five sites. The symptoms developed at leaf Cl concentrations of 1.5% dry weight and the severity of symptoms increased with leaf Cl concentrations. At another site, a zero K treatment was compared to several rates of KCl (300–1500 kg/ha) and K2SO4 applied at equivalent rates of K in factorial combination with two N fertilizer rates. This site had received KCl and developed severe leaf breakdown in the previous season. Leaf Cl concentrations on the zero K and K2SO4 treatments were higher in this experiment (1.7–2.1% dry weight) than at the other five experimental sites (0.6–1.3%), and at this site mild leaf breakdown symptoms developed on these treatments. Leaf N concentrations were greater, while leaf Cl concentrations and the severity of symptoms were less at the higher N rate. At all of the experimental sites that developed leaf breakdown symptoms, the severity of symptoms increased with the rate of KCl application and were significantly correlated to leaf Cl concentrations but not other leaf nutrient concentrations.
Notes
Present address: Peat Research Centre, Newbridge, Co. Kildare, Ireland.