ANNUAL REPORT, 1936 83 



Mcintosh and Baldwin trees were grouped so that one group received no lead 

 arsenate spray after the calyx, another group received no lead arsenate spray 

 after the first cover, and so on through all of the cover sprays. Representative 

 samples were selected from trees in each group and analyzed for lead and 

 arsenic residue. The following table shows the results of the analysis on 

 Mcintosh. The analysis on Baldwin has not been completed. 



Grains per pound of fruit 



Date of Last Application of Lead Arsenate 



Arsenic 



Lead (Pb) trioxide 



(AS2O3) 



Calyx — May 20 .003 00105 



1st cover — May 28... 003 .0021 



2nd cover — June 5 0075 .0051 



3rd cover — July 14 015 .0077 



4th cover — July 30 024 .0165 



These results are in accord with those obtained in previous tests and indicate 

 that when lead arsenate in the form of spray is applied as recommended in 

 the official spray schedule within eight weeks of harvest there is a possibility of 

 the lead and arsenic residue exceeding the tolerance of .018 gr. per lb. for lead 

 and .01 gr. per lb. for arsenic trioxide established by the United States Food 

 and Drug Administration. Previous experiments have shown conclusively 

 that if dust is used instead of a spray for the 3rd and 4th cover applications, the 

 residue from both lead and arsenic is confined well within the limits of tolerance. 



The Nutrition of the Highbush Blueberry, Especially in Relation 

 to Soil Reaction. (J. S. Bailey.) In October 1936 the work on the nutrition 

 of blueberries was organized as a Bankhead-Jones project. 



The experiment to try out the acidification of the soil under field conditions 

 started in 1935 was continued during 1936. In the Brooks nursery the plants 

 growing in the soils treated in 1935 with sulfur, with aluminum sulfate, and with 

 aluminum chloride all made better growth than those in the untreated soil. 

 Also the leaves of the plants in the treated soils were much darker green in 

 color. The plants in the soil treated with aluminum sulfate appeared the best. 

 This difference was distinctly noticeable by the middle of July. 



A similar experiment was started in a nursery set on the Harlow farm in 1936. 

 One plot was left untreated, another received aluminum sulfate at the rate 

 of 400 pounds per acre, and another aluminum sulfate at the rate of 800 

 pounds per acre. These treatments were replicated three times. The pH 

 changes in the plots were as follows: 



Plot pH Plot pH Plot pH 



Treatment No. No. No. 



5/18/36 9/1/36 5/18/36 9/1/36 5/18/36 9/l/36 



Untreated 1 5.55 5.25 4 5.60 5.50 7 5.55 5.30 



400Al 2 (SO4)3 2 5.65 5.30 5 5.70 5.50 8 5.25 5.20 



800Ah(SO4)3 3 5.60 5.40 6 5.60 5.30 9 5.20 4.70 



The pH of all plots decreased during the season. The plants have shown 

 no differences in response to the differential treatments. 



In the spring of 1936 an experiment was started to test out several materials 

 as soil acidifiers for blueberries. The materials used were sulfur, aluminum 

 chloride, aluminum sulfate, citric acid, hydrochloric acid, and phosphoric acid. 

 Lime and untreated soil were used for comparison. The chemicals were each 

 used at four different rates of application. Three-gallon glazed earthenware 

 crocks were used to hold soil and plants. Ten kilograms of treated soil were 



