2 CIRCULAR 411, U. S. DEPARTMENT OF AGRICULTURE 



METHODS 



Essentially the same methods were employed in all the experi- 

 ments. In each experiment the dust mixtures were applied to several 

 plots. By dropping one plot each time the applications were made, 

 a series of plots was obtained which had received applications varying 

 by one successively from the minimiun to the maximum number. 

 Undusted plots were provided as checks in all of the experiments. 



MATERIALS TESTED 



At Charleston, in experiments 1 to 4 ^season 1932-33), paris green 

 and lime (1 to 10) and lead arsenate and lime (1 to 5) were used. The 

 desired rates per acre per application were 16.5 pounds of the paris 

 green-lime mixture and 24 pounds of the lead arsenate-lime mixture, 

 and these were approximated quite closely. In experiments 5 and 6 

 (season 1933-34) paris green and lime (1 to 9) and undiluted calcium 

 arsenate were used. The desired rate per acre per application of 

 each was 20 pounds, and this was approximated quite closely. 



At Baton Rouge, in experiments 1 to 3 (season 1932-33), paris 

 green and lime (1 to 10) and calcium arsenate and lime (1 to 5) were 

 used. The rates per acre per application applied in these experiments 

 ranged from approximately 10 pounds of the dust mixtures on the 

 plots receiving the minimiun number of applications, which were made 

 when the plants were small, to approximately 20 pounds in the later 

 applications on the plots receiving the maximum number. During 

 the season of 1933-34, in experiments 4 and 5, mixtures of paris green 

 and lime and calcium arsenate and lime, each containing 10 percent 

 and 5 percent of arsenic trioxide, respectively, or the equivalent, were 

 used. The dust mixtures were applied at the rates of 10 pounds of 

 the 10-percent and 20 pounds of the 5-percent mixture per acre per 

 application. In experiment 6, paris green and lime (1 to 9) and 

 undiluted calcium arsenate were used and applied at the rate of 

 approximately 15 pounds per acre per application. 



Hydrated builders' lime was used in all of the mixtures given above. 

 The analyses of the arsenicals employed are given in table 1. 



Table 1. — Analyses of arsenical materials used in experimental dusting of cabbage 

 at Charleston, S. C, and Baton Rouge, La. 







Paris 



green 





Constituents or properties 



At Charleston 



At Baton Rouge 





Experiments 

 1 to 4 



Experiments 

 5 and 6 



Experiments 

 1 and 2 



Experiments 

 3 to 6 





Percent 

 0.4 

 57.1 

 .23 

 30.7 

 .66 



Percent 



0.66 



56.76 



.38 



30.98 



1.04 



Percent 

 0.52 



55.38 



. 54 



32^01 



1.34 



Percent 









69 



Copper oxide (CuO) ... ._ 



31 23 





.87 







