Based on the critical levels suggested by Uriu and Koch and Heeney 

 et al . , it would appear that the zinc level in some Mcintosh apple trees 

 in Massachusetts may be at the critical level. Whether or not zinc 

 treatments would be of value in some orchards is not known. For example, 

 the trees in Orchard 1 (Table 1) are very vigorous and productive and 

 exhibit no apparent visual symptoms of zinc deficiency. In fact, no 

 definite visual symptoms of zinc deficiency have been observed on any 

 of our visits to orchards. Benson, in Washington state, has said that 

 the best guide to zinc needs in the Pacific Northwest is the visual ap- 

 pearance of symptoms. It will be of interest to examine trees in or- 

 chards 16 and 17 for visual symptoms of zinc deficiency in 1967. 



Effect of Zinc Level on Tree Performance 



In 196M-, a soil management experiment was established in a block 

 of 3 -year-old Mcintosh trees on EM VII in Shelburne, Mass. Since the 

 nutritional status of these trees was known, it was of interest to com- 

 pare tree performance as related to 2 levels of zinc by comparing the 

 performance of those trees with 20+ ppm with those having 12 or 13 ppm 

 in 1965. The calcium, magnesium, phosphorous, manganese, and iron levels 

 of the "high" and "low" zinc trees did not differ, but nitrogen and po- 

 tassium were somewhat higher in the "high" zinc trees. 



Table 2- Terminal growth and fruit color of Mcintosh as related to 

 2 levels of zinc. 



9 



1^ 



.££ 



m 



23.6 

 12.7 



21.6 

 13.2 



in 



18.8 

 21.4 



in 



15.1+ 

 15.6 



60 

 61 



69 

 73 



Average of 15 terminals 



Percent red color, average of 20 fruits 



Although the experiment was not established to determine the re- 

 sponse of Mcintosh to various levels of zinc, it is apparent that the 

 mean terminal growth and fruit color did not differ between the "high" 

 and "low" zinc trees (Table 2) . Since the trees with 12 or 13 ppm in 

 1965 are vigorous and show no visual symptoms of zinc deficiency, the 

 critical level for zinc in Massachusetts appears to be below this level. 



Soil Applications of Zinc 



Soil applications of zinc sulfate have generally been unsatisfac- 

 tory for the correction of zinc deficiency in apple orchards except 

 occasionally on acid soils. Since our orchard soils are acid and tests 

 with soil applications of zinc are more convenient than spray applica- 

 tions in grower orchards, a study of the effectiveness of a soil appli- 

 cation of zinc sulfate for increasing the zinc level in a mature North- 

 ern Spy orchard was established in April, 1965. No increase in zinc 

 level occurred in the leaves during the year of application (1965) or 



