Impacts of preharvest fall sprays of calcium chloride at high rates on quality and ‘Conference’ pear storability

Abstract

The aim of the study was to examine effects of preharvest fall sprays of calcium chloride (CaCl2) at high rates on quality and ‘Conference’ pear (Pyrus communis L.) storability. The experiment was carried out during 2011–2013 in central Poland, on mature pear trees grafted on Quince S1 (Cydonia oblonga Mill.), planted on a coarse-textured soil with low level of organic mater. The trees were sprayed with CaCl2 six times during a growing season. The first spray treatment was made 6 weeks after full bloom and the last one - 7 days before harvest. The doses of CaCl2 in the first fifth spray measures (summer sprays) were 2–5kgha−1, whereas in the last treatment (fall spray): 5, 10, 15, 20 or 25kgha−1. The trees unsprayed with Ca served as the control. The results showed that fall sprays of CaCl2 at increased rates (10, 15, 20 and 25kgha−1) injured leaves. The most intensive leaf burn was recorded as a result of fall spray of CaCl2 at a rate of 25kgha−1. The above spray treatment caused also defoliation; however, it did not affect cold damage of flower buds. CaCl2 sprays had no influence on yield, mean fruit weight, russeting and peel color, and flesh firmness, soluble solids concentration (SSC) and titratable acidity of fruit at harvest. >Pears sprayed with >CaCl2 had increased Ca status; the most Ca was found in fruit treated with CaCl2 in the summer and in the fall at doses of 20 and 25kgha−1. All spray treatments of CaCl2 inhibited production rates of ethylene (C2H4) and carbon dioxide (CO2) by fruit at harvest. After storage, pears sprayed with CaCl2 in the summer and the fall at rates of 20 and 25kgha−1 produced less C2H4 and CO2, contained more organic acids, and were firmer, greener and less sensitive to internal browning than the control fruit. It is concluded that fall sprays of CaCl2 at a rate of 20 or 25kgha−1 should be recommended in ‘Conference’ pear orchards, as supplement of summer Ca sprays, to improve fruit storability.