CHLORIDE-INDUCED LEAF BREAKDOWN IN KIWIFRUIT

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 or chards of kiwifruit (Actinidia deliciosa [A. Chev] C.F. Liang et A.R. Ferguson var. deliciosa cv. Hayward). Leaf breakdown (marginal leaf sc orch followed by necrosis and leaf drop) was induced by KCl applicatio n at four of the five sites. The symptoms developed at leaf Cl concent rations of 1.5% dry weight and the severity of symptoms increased with leaf Cl concentrations. At another site, a zero K treatment was compa red to several rates of KCl (300-1500 kg/ha) and K2SO4 applied at equi valent rates of K in factorial combination with two N fertilizer rates . This site had received KCl and developed severe leaf breakdown in th e previous season. Leaf Cl concentrations on the zero K and K2SO4 trea tments were higher in this experiment (1.7-2.1 % dry weight) than at t he other five experimental sites (0.6-1.3%), and at this site mild lea f breakdown symptoms developed on these treatments. Leaf N concentrati ons were greater, while leaf Cl concentrations and the severity of sym ptoms were less at the higher N rate. At all of the experimental sites that developed leaf breakdown symptoms, the severity of symptoms incr eased with the rate of KCl application and were significantly correlat ed to leaf Cl concentrations but not other leaf nutrient concentration s.