QUALITY AND 'CONFERENCE' PEAR STORABILITY AS INFLUENCED BY PREHARVEST SPRAYS OF CALCIUM CHLORIDE

The aim of the study was to examine impacts of calcium chloride (CaCl2) sprays on quality and 'Conference' pear (Pyrus communis L.) storability. The experiment was carried out during 2002-2008 at a commercial orchard in Central Poland, on mature pear trees grafted on Quince S1 (Cydonia oblonga Mill.). The trees were planted at a spacing of 3.5 x 1.5 m, on a coarse-textured soil with low organic matter status, optimal pH, and adequate contents of available macro- and micronutrients. The efficiencies of two, four, or six sprays of CaCl2 were examined. The first treatment in all CaCl2 spray combinations was made six weeks after full bloom (the end of June), and the last one two weeks before harvest. Intervals between measures in the combinations of four and six sprays of CaCl2 were 4 and 2 weeks, respectively. A rate of CaCl2 depended on the tree growth stage; up to mid July a dose of CaCl2 was 2 kg ha(-1), whereas in the later period 4 kg ha(-1). Calcium chloride sprays were made at a volume of 1000 dm(3) of water per ha. The trees unsprayed with CaCl2 served as the control. Because in 2005 and 2007 most flowers were damaged by spring frost, CaCl2 sprays in those years were not performed. The obtained results demonstrated that CaCl2 sprays did not affect fruit yield, mean fruit weight, fruit russeting, and ground skin color, soluble solids concentration (SSC), and titratable acidity of fruit at harvest. At harvest, in 2 out of 5 years of the study, pears sprayed six times with CaCl2 had increased firmness, and decreased values of both starch index and Streif's index. Only six sprays of CaCl2 enhanced pear Ca level. After storage (150 days at 0 degrees C plus two days at room temperature) pears sprayed six times with CaCl2 were firmer, greener, and less sensitive to internal browning than those of the control plots. In three out of five years, pears sprayed six times with CaCl2 contained more organic acids after storage than the control fruit. Preharvest CaCl2 sprays had no effect on SSC in pears and their decay after storage. It is concluded that in 'Conference' pear orchards six preharvest sprays of CaCl2 should be applied to improve fruit storability.