22- 



the grassed alley appeai'ed deeper and more sparse. 



Herbicides indirectly affect the nutrition of fruit trees 

 because killing of vegetation under the trees reduces the com- 

 petition between the grass and tree roots for minerals and 

 water. Furthermore, herbicides will decrease soil pH and ad- 

 versely affect earthworm populations and thereby soil structure. 



Effects of Fertilization on Fruit Quality 



Calcium : In 1936 bitter pit was found to be related to low Ca 

 levels in apples. Thirty years later it could still be stated 

 that "Inspite of the very low Ca status of many orchards soils., 

 there have been few reports of direct responses by bearing apple 

 trees to Ca . . . " ( Temperate to Tropical Fruit Nutrition , Norman 

 F. Childers, Editor) . Today , however , there is strong concern 

 about Ca levels in apples and pears just about anywhere in the 

 world that they are grown . 



At first, this concern was directed at bitter pit and cork 

 spot but today we know that many physiological disorders may be 

 at least partly related to low Ca levels in the fruit. In Vv-armer 

 fruit growing areas, cork spot and bitter pit remain the most 

 serious effects of low Ca, but in cooler areas various forms of 

 internal breakdown are the most serious Ca-def iciency problem. 

 In British Columbia, Canada, the 'Spartan' apple industry was 

 almost destroyed by breakdown problems before methods of raising 

 fruit Ca levels were successfully developed. 



Nitrogen : Excessive amount 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, inter- 

 nal browning, and internal breakdown during and after storage. 



Excessive N levels are probably very common but deficient 

 levels rarely occur. In the Pacific Northwest it has been esti- 

 mated that 50 to 751 of apple orchards and a smaller percentage 

 of pear orchards, are excessively high in N. The effects of high 

 N on apples are perhaps being masked at harvest by use of growth 

 regulators, especially Alar, but growth regulators cannot mask 

 their consequences after storage. 



Potassium : K deficiency has only a mild effect on fruit quality, 

 reducing acidity of the fruit and reducing red coloration. Ex- 

 cessive amounts of K in fruit are a greater danger to fruit quality, 

 since they lead to increased scald, bitter pit, and internal break- 

 down after storage. 



