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THE EFFECT OF SUMMER PRUNING OF McINTOSH APPLE 

 TREES ON THE CALCIUM NUTRITION AND POSTHARVEST 

 QUALITY OF THE APPLES 



William J. Bramlage and Mack Drake 

 Department of Plant and Soil Sciences 



As we have searched for methods to increase the amounts of 

 calcium (Ca) in apples, we have become interested in the results 

 from Europe indicating that late summer pruning can improve Ca 

 nutrition of the fruit. It is logical to expect such a result 

 from late-summer pruning, since vegetation and fruit are competing 

 for what Ca is available within the tree, and vegetation is the 

 much stronger competitor. Therefore, removing vegetation late 

 enough so that regrowth does not occur should reduce much of the 

 competition and allow more of the available Ca to move into the 

 fruit . 



But, will it work? To test the idea, we adopted the pruning 

 technique of A. P. Preston in England, which he found to work under 

 their conditions. This is a very severe pruning technique: all 

 current-year shoots are removed to their points of origin . We 

 applied this technique to 8 vigorous 12-year-old Mcintosh trees on 

 M.7 rootstock in 1975 and in 1976 within an experiment where we 

 were testing various methods of raising the Ca level in the fruit. 

 Pruning was done in early- August , 1 month before harvest, and 

 resulted in no regrowth in that season. 



The effects of the pruning on the quality of the fruit were out- 

 standing. Ca content of the fruit at harvest in 1975 was 15% above 

 that of fruit from trees that had not been summer-pruned. Due to 

 reduced foliage, light penetration was much greater and the fruit 

 were much redder at harvest; however, there was no sun- scald on them 

 (although sun-scald did occur on Cortlands that were pruned in the 

 same way). After storage in either regular storage to January, or 

 in CA until mid-April, apples from the summer-pruned trees had much 

 less bitter pit, breakdown, and rot. 



In 1976, the same trees were again pruned in the same way. 

 Again, the fruit were highly colored due to the excellent light pene- 

 tration, but were not sun-scalded. In this second year, summer 

 pruning increased fruit Ca by an amazing 60?;, and after storage the 

 quality of the fruit was outstanding: bitter pit and breakdown had 

 been virtually eliminated, and the fruit were substantially firmer 

 than ones from trees that were not summer pruned. Clearly, summer 

 pruning had effectively increased the amount of Ca in the apples and 

 had correspondingly improved their postharvest quality. 



Should you consider using this pruning technique in your orchard? 

 We do not think so; we do not believe that the Preston technique can 

 be applied in New England without modification. We believe it is too 

 severe a method of summer pruning for Mcintosh in Massachusetts. Among 

 our concerns is the fact that in 1976 the trees produced many blossoms 

 at harvest time. 



