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The K requirements of apple trees with a large crop are high 

 because the fruit utilizes about 3 times as much K as N. Since 

 the quantity of K stored by the tree is extremely small, it seems 

 important to supply adequate K this spring on trees that had heavy 

 fruit set in 1982. 



The requirements of apple trees for K (expressed as K2O), based 

 on potential yields, are as follows: (a) less than 15 bu: 1.3 lbs. 

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

 25 bu: 2.7 to 4.3 lbs/tree. It is necessary, however, to maintain 

 a balance among the essential nutrients for apple trees. For 

 example, excessive levels of K can reduce both leaf and fruit Ca. 

 Therefore, we strongly urge that you participate in our leaf 

 analysis program to more accurately determine the K needs of your 

 apple trees . 



Calcium CCa) : Our suggestions for meeting the Ca needs of apple 

 trees can be found in another article in this issue of FRUIT NOTES. 



Boron (B) : B can be supplied to apple trees either by foliar 

 or soil applications. Use the most economical and convenient 

 method. However, it is safest to apply all elements as a fertilizer 

 except in emergency situations . 



Soil applications of boron should be applied to orchards every 

 3 years. The rate of application per tree vary with tree age and 

 size. In low density orchards, apply h pound of borax (11.1° 

 actual B) or its equivalent under young trees coming into bearing , 

 h to 3/4 pound to medium age and size trees and 3/4 to 1 pound to 

 large or mature trees. Be sure to note the percent actual B in 

 the fertilizer being used to supply this element . B containing 

 fertilizers vary from approximately 11 to T\\ actual B. 



In medium and high density orchards (115 trees/acre or higher), 

 it might be best to apply B on an acre basis. We suggest the follow- 

 ing rates per acre of borax (11.1% actual B) or its equivalent: 

 (a) trees 4 to 7 years of age - 12 lbs; (b) trees 8 to 15 years of 

 age - 12 to 24 lbs; and (c) trees 16 to 30 years of age - 24 to 

 48 lbs. 



When the soil application of B is followed by a wet spring, 

 it may be advisable to apply 2 foliar applications of B the follow- 

 ing year. 



Many growers now rely on annual foliar applications of B. The 

 usual practice is to add Solubor to the first 2 cover sprays. 

 Fertilizer grades of borax may contain grit and should not be used 

 in a sprayer. Mature trees should receive 4 pounds of Solubor per 

 acre each year. Consequently, the goal is to apply about 2 pounds 



