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Reduce or omit N on young, vigorous Mcintosh trees if they 

 are starting to bear a crop, in order to avoid excessively large, 

 poorly colored fruit. Young vigorous, non-bearing Mcintosh apple 

 trees may have N levels of 2.4-2.6%, but these N levels should be 

 reduced when trees start to produce. 



Apply sufficient N to keep bearing Delicious trees vigorous. 

 N levels of 2.2-2.41 in bearing Delicious trees are probably sat- 

 isfactory because it is necessary to keep the tree vigorous in or- 

 der to produce large-sized fruits. Furthermore, obtaining suffi- 

 cient red color on the newer strains of Delicious is not a problem. 



The N requirement can be met by applying calcium nitrate, am- 

 monium nitrate or urea sources of fertilizer N or a "complete" fer- 

 tilizer. (Growers concerned about bitter pit and/or cork spot may 

 wish to rely on calcium nitrate as the source of N.) However, the 

 phosphorous (P) in the complete fertilizer is not needed in our 

 orchards and fertilizer is in short supply. Therefore, we strongly 

 urge growers to purchase a prepared mix such as 15-0-14 which con- 

 tains no P or to purchase an N and a K fertilizer and mix them prior 

 to application, or apply them separately. 



Potassium (K) : Results of the leaf analyses for the 1973 season 

 indicated that K levels were generally low in our apple trees. The 

 K requirements of apple trees in a heavy crop year are high since 

 the fruit utilizes about 3 times as much K as N. Secondly, the 

 quantity of K stored by the tree which is available for utilization 

 is extremely small in comparison with N. Thus, it seems important 

 to supply adequate K this spring in anticipation of a heavy crop 

 year. The requirements of apple trees for K (expressed as K7O) 

 based on potential yields are as follows: (a) less than 15 bu: I.3 

 lbs/tree; (b) 15 to 25 lbs: 1.3-2.7 lbs/tree; and (c) more than 25 

 bu: 2.7-4.3 lbs/tree. It is necessary, however, to maintain a bal- 

 ance among the essential nutrients for apple trees. Excessive lev- 

 els of K can reduce both leaf and fruit Ca. Therefore, you should 

 attempt to maintain K levels in apple leaves in the range of 1.25 

 to 1.60%. 



Calcium (Ca) : As expected, Ca in our apple leaves in 1973 contin- 

 ued to be considerably less than the supposedly desirable content 



of 1.25-1.50%. Bitter pit was more prevalent than usual on Mcintosh 

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*Trade name 



