G. Neilsen, D. Neilsen, S. Dong
Oct 1, 2005
Citations
3
Influential Citations
37
Citations
Journal
Hortscience
Abstract
Calcium application trials were undertaken in a 'Braeburn' apple (Malus ×domestica Borkh.) orchard with a history of bitter pit development at harvest. In 2000, an early season calcium chloride application strategy was compared with the unsprayed control and a late season application strategy. From 2001-03, the assessment of timing of calcium chloride sprays was extended by comparing effects of fi ve weekly sprays ap- plied during the growing season either early, middle, or late season. Other Ca applica- tion strategies tested included sprays of acidifi ed calcium carbonate suspensions and soil application of calcium thiosulphate. In the fi rst experiment, early application of calcium chloride reduced the occurrence of bitter pit at harvest and after 3 months cold air stor- age, despite having low harvest fruit Ca concentrations. Late sprayed fruit had a higher incidence of bitter pit. In the second experiment, the later calcium chloride was sprayed in the growing season, the higher the fruit Ca concentration at harvest. Despite this, no bitter pit was measured at harvest for 2 years for early and midseason calcium chloride spray regimes. In 2003, when Ca disorders were severe and fruit large, bitter pit was observed despite early season calcium chloride sprays. Soil calcium thiosulphate application and foliar sprays of acidifi ed calcium carbonate suspensions failed to meaningfully augment harvest fruit Ca concentrations and affect bitter pit incidence. The importance of achieving adequate Ca supply for optimising the quality of apple fruit has stimulated research in the major fruit growing regions of the world to increase fruit Ca concentration and thereby improve fruit quality. The preferred method to increase fruit Ca concentration has been via preharvest foliar Ca sprays, as indicated from numerous research reviews summarizing fi eld trials from many regions (Bramlage et al., 1980; Terblanche et al., 1980; Vang-Petersen, 1980). Recom- mendations based upon this early research usually involves application of three to six sprays of soluble Ca salts (usually chloride or nitrate salts) throughout the growing season. Limited consideration has been given to time of Ca application since many spray rate ap- plication experiments have been confounded by application at different times (Le Grange et al., 1998b). Several laboratory studies using Ca pressure-com- pensating drip emitters located 0.5-m either side of the tree within the row. Irrigation was applied to meet daily requirements based on water demand as estimated by the previous day's evaporation from an atmometer (ET Gage Co., Loveland, Colo.) linked through a datalogger (CR10X; Campbell Scientifi c, Logan, Utah) to irrigation controls. Throughout the experimental period, trees were fertigated with potassium nitrate (13N-0P-37K) for a 6-week period commencing in early June at a constant irrigation solution N-concentration of 112 mg·L -1