THE EFFICIENCY OF DIFFERENT FOLIAR-APPLIED CALCIUM MATERIALS IN IMPROVING APPLE QUALITY

The aim of this study was to examine the efficiency of sprays of different commercial calcium (Ca) materials on apple quality and storability. The experiment was carried out in 1998-1999 at Dabrowice Experimental Orchards of the Research Institute of Pomology and Floriculture, Skierniewice, Poland on mature ‘Szampion’ apple trees planted on a sandy loam soil at a spacing of 4 x 2.5 m. Trees were fives times sprayed with Rosatop Calcium [22% Ca as Ca(NO₃)₂], Rosafos (4% Ca as CaHPO₄), Rosacal [19% Ca as Ca(NO₃)₂], or calcium chloride (29% Ca). Trees sprayed with water served as the control. The first spray was applied 6 weeks after full bloom and the next ones at 2-week intervals. The results showed that Ca sprays had no effects on fruit yield, mean fruit weight, colour and fruit maturity at harvest. Calcium-containing sprays did result in no leaf injury. The highest Ca concentration and the lowest K/Ca ratio in fruit flesh tissues were reported as a result of sprays of Rosatop Calcium. Foliar applications of Rosacal and CaCl₂ also increased levels of Ca and lowered K/Ca ratio values in fruit flesh, however they were less effective than Rosatop Calcium sprays. Calcium sprays, except for Rosafos, reduced the number of apples affected by bitter pit. Calcium sprays also increased fruit resistance to internal breakdown but had no effects on firmness, soluble solids concentration and sensitivity of fruit to pathogens during storage. The results indicate that sprays with Rosatop Calcium and Rosacal were generally as effective in improving apple storability as CaCl₂. However, Rosatop Calcium sprays were more effective in increasing fruit Ca compared to CaCl₂ or Rosacal. Therefore, Rosatop Calcium should be recommended in apple production, for varieties sensitive to Ca-related physiological disorders.