clum content of the skin fi^om normal apples is double that of pitted 

 fruit and in several cases the magnesium is higher in the skin of pit- 

 ted than in normal fruit. Recent evidence Indicates it is not simply 

 the level of calcium, but the relative balance of calcium to nitrogen, 

 to magnesium, to potassium and to boron which must be considered. For 

 example: Yamazaki and Mori, from Japan, show that bitter pit in Jona- 

 than apples occurred when calcium was absent from the nutrient solution 

 and that it was increased by added nitrogen at each of 3 levels of cal- 

 cium nutrition. Rose et al, of the U.S.D.A., reports that adding mag- 

 nesium (Epsom salts) to irrigation water produces symptoms similar to 

 Baldwin spot, indicating the importance of the calcium-magnesium ratio 

 in apple nutrition. Garman and Mathis , at the New Haven Experiment 

 Station in Connecticut, reduced bitter pit by injecting a calcium salt 

 solution through the calyx-end while the apple was growing on the tree, 

 and induced bitter pit by injecting a magnesium solution. They report 

 that the magnesium to calcium ratio was 4 to 1 in pitted and 1 to 1 in 

 normal fruit. Baxter, in Australia, reported that this disorder can be 

 artificially induced by a calcium deficiency brought about by spraying 

 the leaves with a magnesium salt solution or by injecting calcium che- 

 lating agents . 



Cation Balance . The 

 sum of the nutrient cations 

 (calcium + potassium + mag- 



ml: 



BlTTEFi Pir 



Fig. 1. Bitter pit on Baldwin apples. 

 The top row of apples show only a slight 

 indication of the disorder; whereas, the 

 remainder of the fruit are severely pitted. 



nesiumj in tissue of a given 

 plant species tends to be a 

 constant. Leaf potassium is 

 higher and calcium and mag- 

 nesium are lower with a light 

 as compared to heavy crop. 

 Thus, if leaf potassium is in- 

 creased by fertilizer appli- 

 cation or by crop size, cal- 

 cium and magnesium will be 

 depressed. If leaf potas- 

 sium is low, calcium and mag- 

 nesium will be relatively 

 high. Likewise, increasing 

 the level of magnesium in 

 the leaf, reduces calcium and 

 potassium, while in contrast 

 increasing leaf calcium reduces 

 magnesium and potassium. Al- 



though, leaf calcium usually 

 is low for those trees with pitted fruit, Massachusetts research shows 

 that for a given calcium level in the leaf, a greater incidence of bit- 

 ter pit is associated with a relatively high leaf magnesium or potassium 

 level. This illustrates the importance of maintaining a desirable bal- 

 ance of the nutrient cations, calcium, potassium and magnesium, in the 

 leaf tissue. Because calcium moves slowly into the soil and through the 

 conducting tissue of the tree, foliar fertilization by spraying with cal- 

 cium salt solutions, is required to raise the level of calcium quickly 

 in the apple leaf and conducting tissue. Garman and Mathis compared 



