often recommended to maintain Ca uptake by the tree roots. 



Foliar sprays with Ca salts are the most direct way of insur- 

 ing adequate fruit Ca levels during growth. There is little move- 

 ment of Ca into fruits by the tree as long as vegetative growth 

 is abundant, so the value of sprays is that it places Ca directly 

 on the surface of the fruit, where it can be taken in by the fruit 

 if conditions are appropriate. At first, Ca (NO ) sprays were 

 recommended, but tests with many other Ca compounds have shown that 

 calcium chloride (CaCl ) is generally the most effective material. 

 Leaf injury from CaCl can prevent its use in many growing areas, 

 but in Northern North America it can be used if proper precautions 

 are taken. Frequent applications throughout the growing season 

 are usually the most effective way of applying CaCl„. A single 

 massive application shortly before harvest substantially raises fruit 

 Ca and improves keeping quality of apples. This idea originated in 

 British Columbia and we have tested it extensively, but we believe 

 that the severe foliar damage, the potential for fruit injury or 

 preharvest drop, and the residue that may be objectionable in hand- 

 packing operations make it an unlikely commercial practice. 



Post-harvest dips in CaCl „ -containing solutions reduce soften- 

 ing and breakdown during storage. The use of a thickening agent 

 greatly increases the effectiveness of a dip, but thickeners leave 

 an objectionable residue that can be very difficult to remove. High 

 concentrations of CaCl„ must be used, and these can cause corrosion 

 of metal and injury to fruit, and may also leave a noticeable resi- 

 due. However, in the appropriate circumstances much benefit can 

 be obtained from a dip. In New England, fruit growers have preferred 

 foliar sprays, but postharvest dips are an alternative. 



Nitrogen . To stimulate growth of young trees, N is usually 

 applied at high rates. Fertilizer rates should be reduced when 

 cropping begins, but they are sometimes continued because yields can 

 be increased. Even when N application is reduced when cropping begins, 

 the trees may continue to be supplied with excessive amounts of N 

 from the large reserves that have accumulated in the soil, sod and 

 tree. We have found that high N levels in trees fall very slowly 

 even when no additional N fertilizer is supplied. 



Excessive amounts of N in the tree and fruit can severely reduce 

 fruit quality. The vigorous growth that it encourages reduces the 

 Ca level of the fruit. Moreover, the high N fruit tend to be larger, 

 greener, softer, more subject to preharvest drop, and to have more 

 cork spot and bitter pit. These fruit also tend to develop greater 

 amounts of scald, bitter pit, internal browning, and internal break- 

 down during and after storage. 



Over-fertilization with N is probably very common. In the Paci- 

 fic Northwest it has been estimated that 50 to 75% of apple orchards. 



