aircraft, the original deposit of 34 p. p.m. happened to be the average of the 

 original deposit of the two turbine-applied plots. The zero day deposits 

 increased as the dosage increased but not in mathematical proportion. 



All plots were sampled 7 to 8 days after application. At this time inter- 

 val from 44 to 65 percent of the original deposit had disappeared from the 

 range grass. Where 4, 6, or 16 oz. per acre was applied as a water emulsion by 

 turbine sprayer, the rate of loss of the original deposit at 21 days after 

 application was 83, 81, and 85 percent, respectively. 



Diazinon was applied at rates of 4, 6, and 8 oz, per acre by modified 

 turbine (Buffalo Turbine) sprayer. The zero day deposits did not increase in 

 the same proportionaas the rates of application. The initial deposit resulting 

 from the 8-oz. application was slightly less than the initial deposit found on 

 one of the 4-oz. treated plots. The rate of disappearance of diazinon was 

 rather rapid, with an average of 72 percent of the initial deposit lost in the 

 first 3 to 4 days. Seven to eight days after application, an average of 86 

 percent of the original deposit had been lost from the range grass. Twenty-one 

 days after application, an average of 92 percent or more of the original resi- 

 due had disappeared from the grass. 



Dimethoate was applied as a water-emulsion and an oil-concentrate spray. 

 Applications were made by turbine spi*ayer and two types of aircraft. Where 1, 

 2, 3, and 4 oz. per acre were applied as a water-emulsion spray by ground rig, 

 the original deposits on range grass did not correlate with the increase in 

 dosage per acre. Where the watei*-emulsion spray was applied by TBM aircraft, 

 doubling the dosage resulted in almost a sixfold increase in original deposit, 

 'iirh.sn 3 oz. per acre was applied by aircraft as an emulsion formulation, the 

 original deposit on the two plots varied almost fivefold. The original 

 deposit resulting from 3 oz. per acre applied by aircraft as an oil-concentrate 

 was nearly the same as the original deposit in one of the plots when the same 

 amount was applied by the same type aircraft as an emulsion. 



Two rates of application were made by use of larger aircraft. When 1,7 

 oz. per acre was applied as an emulsion, the original deposit was considerably 

 lower than when 1 and 2 oz. per acre were applied by ground rig. The residue 

 levels found 1, 3 to 4, and 7 to 8 days after application of the 1.7-oz. rate 

 indicate that the original deposit figure is probably in error. When 3.4 oz, 

 per acre, as an emulsion, were applied by aircraft, the original deposit cor- 

 responded fairly well with the original deposit found on the plots treated 

 with 3 oz. per acre by ground rig. Where more than one plot was treated with 

 the same rate per acre, the original deposits ranged iTom 1.4- to 4.6-fold, 

 Oh the basis of fomiulation and method of application, the highest ivverage 

 deposit per ounce of active material was obtained with the oil concentrate 

 applied by airci^ft. 



Fourteen days after application, from 42 to 97 percent of the original 

 deposit had been lost from the range grass. Seven to eight days after applica- 

 tion, the residue loss from the grass ranged from 66 to 98 percent when two 

 plots were disregarded. The data obtained on these two plots, 1.7-oz. emul- 

 sion applied by TBM and 3 oz. of emulsion formulation applied by Piper air- 

 ci*aft, indicate that the original deposit figures are probably in error by 



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