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POMOLOGICAL REST^ARCH 

 10. Nutrition of the Highbush Blueberry. 



The feeding of highbush blueberries is an exceedingly important part of their 

 cultiu'e. The questions which at once arise are: VJhat should be used and hovf much? 

 Should a ccraplete fertilizer be used? Or should only one or tvro elements, say 

 nitrogen and potassiim, be used? This project v/as started to answer such questions 

 as these and others of a similar nature. 



One of the first problems in nutrition of highbush blueberries involved the 

 yellovmig of the leaves. This was thought to be caused in most cases by a de- 

 ficiency of iron. This trouble is not general in Massachusetts. It occurs in 

 spots and may be quite serious in small areas. The relationships are rather complex 

 and will be discussed in a separate article. 



Severe magnesium deficiency was found in one field several years ago. It has 

 been suspected in other fields. It is not a common deficiency in blueberry fields 

 but where it becomes serious it can very inaterially reduce both size of crop and 

 size of berries. It is fairly easily remedied by soil applications of epsom salts 

 or dolomitic liiaestone. The latter must be light unless the soil is veiy acid, A 

 recent attempt to correct magnesium deficiency by spraying epsom salts on the 

 leaves was unsuccessful. Since the blueberry leaf is very waxy and sheds sprays 

 very readily, this is not surprising. Soil applications of chelated magnesium were 

 not effective either. 



Blueberries, as is the case with other fruit plants, give the quickest and 

 greatest response to applications of nitrogen. Tlierefore, the nitrogen alone pro- 

 gram might have been adopted by blueberry growers if it hadn't been learned early 

 in the life of the industry that a complete fertilizer vforked best in the field. 

 The use of nitrogen alone for a number of years may affect fruits adversely in tvYO 

 ways. First, the failure to apply other elements and the increased denard f or them 

 resulting from increased grovrth followin.;^ the nitrogen application may cause a de- 

 ficiency of one or more elements. Second, the excess of nitrogen in relation to 

 the other elements may upset the nutritional balance of the plant v/ith consequent 

 reduction in growth and yield. 



Nutritional balance in a number of fruit plants has been under study for several 

 years. The usual method is to analyze the leaves chemically for nitrogen, phosphorous, 

 potassiujn, calcium, magnesi\im, and sometimes other elements, The amount of each 

 elei.ient is then studied in relation to its effects on other elements, on yield, 

 color, quality of fruit, etc., and on their inter-relationships. 



This type of nutritional study has been very scanty in the case of cultivated 

 blueberries, A few leaf analyses have been published but these have not been suffi- 

 cient for a thorough study. Results published from this station in 19h9 showed 

 that the highbush blueberry appears to have a very low phosphorous requirement. 



