|Authors: ||G. Lang, C. Guimond, S. Southwick, F. Kappel, J.A. Flore, T. Facteau, A. Azarenko|
|Keywords: ||Prunus avium, water potential, osmoticum, salt, automation|
Automated cyclical overtree sprinkler applications of dilute calcium chloride solutions to reduce rain-induced sweet cherry fruit cracking was conceptualized in Michigan in 1994. Orchard trials were expanded to Washington in 1995 and regionally (California, Oregon, Washington, British Columbia, and Michigan) in 1996–97. In general, positive results have been reported in all test locations, with some spectacular successes (two- to five-fold reductions in cracked fruit) along with a few tests giving no or only marginal improvement.
Limitations to success appear to be due primarily to technical equipment difficulties or a need to further refine the programmable parameters that monitor current rainfall, initiate or terminate the calcium application cycle, and/or re-set the automated program for the next rain event.
Understanding how to finetune the programmable factors may be particularly important for achieving success across regions with different rainfall patterns or across orchard systems trained to different tree architectures.
Experimental additions to the core protection system (rainbucket, microprocessor-based datalogger, pump, and sprinklers) include different methods of injecting a concentrated calcium stock solution into the sprinkler line, alternative programmable dataloggers, the use of electrical conductivity sensors to monitor calcium solution delivery and reapplication, and alternative forms of osmoticum (calcium chloride, calcium acetate, etc.) to reduce the rate of water uptake from the fruit surface into the mesocarp with minimal foliar phytotoxicity.
Fruit-cracking data and observations from the 1996–97 regional trials are presented.
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