-3- 



more sub zero temperatures. 



— W, D. Weeks 

 I I I I I I I I I I I I I I I I 



BLUEBERRY NUTRITION - A PROGRESS REPORT 



The fertilizing of cultivated blueberries has followed a pattern similar 

 to that which has characterized many other fruits in their early history. It 

 was feared that too much fertilizer, particularly nitrogen, would do more 

 harm than good. As a result, early fertilizer applications were relatively 

 light. These have been gradually increased until rather large amounts are 

 being recommended and used by some growers, amounts which supply 100 or more 

 pounds of actual nitrogen per acre. How much is safe and economical to use? 



Cultivated blueberries appear to respond readily to applications of 

 nitrogen. What their response is to other major elements is uncertain. In 

 New Jersey there seemed to be a response to applications of phophorous. The 

 results of leaf analysis both in Massachusetts and in Michigan suggest that 

 the cultivated blueberry needs very little phosphorous. The situation as re- 

 gards potash is still uncertain. Results from Michigan indicate no relation 

 between amount of leaf potash and yield. 



To get more information about the fertilizer need of cultivated blue- 

 berries, an experiment was set up in a growers field in the spring of 1956, 

 Nitrogen is applied as ammonium sulfate at the rate of 1/2, 1 and 2 pounds 

 per bush. Sul-Po-Mg is used to supply both potash and magnesium because the 

 use of potash alone might result in a magnesium deficiency. The rate is 0, 

 1/2 and 1 pound per bush. These are being used in all possible combinations, 

 this giving nine different treatments. All fertilizer is spread at one time, 

 just before bloom. 



In 1956, all plots were fertilized alike with a complete fertilizer so 

 that yield records of the plots could be obtained before the differential 

 fertilizer treatments were made. Each summer yields are obtained and leaf 

 samples for chemical analysis are collected from all the plots. 



The rates of fertilizer application, especially nitrogen, are high. 

 These high rates were considered advisable because the bushes were in a low 

 state of vigor and because it was desired to find the upper limit of amounts 

 which could be used without injury. 



In 1957, the differences in yields between plots were not significant. 

 This is not surprising when one remembers that the fruit buds for the 1957 

 crop were formed in the summer of 1956 before differential fertilization 

 started. On the other hand, the growth response of the bushes has been very 

 marked. All the bushes have been stimulated into increase growth which ap- 

 pears to be roughly in proportion to the nitrogen applied. When 2 pounds 

 per bush of ammonium sulfate was used, considerable late growth resulted, 

 growth which was quite immature at leaf fall and which will probably be in- 

 jured if very low temperatures occur. It looks as if the limit of safety 

 has been exceeded. This is not surprising since 2 pounds per bush would be 



