2 - 



(spreading) may be needed on vigorous young Delicious trees to en- 

 courage bloom and fruit set. 



Apply sufficient N to keep bearing Delicious trees vigorous. 

 N levels of 2.2 - 2.4% 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. Therefore, purchase a prepared mix that contains no P 

 or purchase an N and a K fertilizer and mix them prior to applica- 

 tion or apply them separately. 



Potassium (K) : 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 1976. 



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: 1.3-2.7 lbs/tree; and (c) more than 25 bu: 

 2.7-4.3 lbs/tree. It is necessary, however, to maintain a balance 

 among the essential nutrients for apple trees. For example, exces- 

 sive levels of K can reduce both leaf and fruit Ca. Therefore, w e 

 strongly urge that you participate in our leaf analysis program to 

 more accurately determine the K needs of your apple trees. 



Calcium (Ca) : It is very difficult to increase Ca content of apple 

 trees and fruit. Although foliar sprays of Ca solutions have been 

 shown to reduce bitter pit, they have not eliminated it. A major 

 problem is that Ca in the soil moves very slowly into the tree and 

 most of it is quickly tied up in an insoluble form. We suggest, 

 the following measures to increase Ca content of apple leaves and 

 fruits. 



A. Continue to apply 3 tons of limestone per acre every 2 to 

 3 years. Where high magnesium lime was used in the last 

 application, the use of a more soluble high Ca, low Mg 

 lime (5-7% MgO) will act more rapidly and will provide 

 more Ca. 



B. Use calcium nitrate as the source of nitrogenous fertiliz- 

 er. Calcium nitrate increases the level of soluble soil 

 Ca more quickly, increases the downward movement of Ca and 

 raises the pH of the soil. 



