887525 



EFFECT OF SOIL APPLICATIONS OF INSECTICIDES 3 



The test insecticides were applied on April 11 and October 26, 

 1949, and on November 15, 1950, before the crops were planted. 

 Aldrin was applied at 4 pounds, chlordane at 20 pounds, and toxa- 

 phene at 20 pounds per acre. These insecticides were applied as 

 sprays made from wettable powder formulations. Applications 

 were made with a power sprayer equipped with a 10% -foot boom 

 with nozzles spaced 12 inches apart. Immediately after application 

 the soil was thoroughly disked 8 inches deep in two directions, to 

 mix the insecticides with the soil (fig*. 2). Ethylene dibromide was 



<'ihm% 



Figure 1. — Three-acre site near Oxnard, Calif., used for studying the effect 

 of soil applications of insecticides on various crops. 



injected into the soil 6 to 7 inches deep, at 12-inch spacings, with 

 a soil-fumigant applicator, the dosage being equivalent to 54 

 pounds per acre. A heavy steel bar attached to the rear of the 

 applicator sealed any openings made by the injector blades. 



To prevent relocation of the insecticides at lower soil depths, the 

 soil was never ploughed. The formation of a plow sole was pre- 

 vented by subsoiling 20 inches deep, at 20-inch spacings, prior to 

 winter rains, on December 5, 1949, and on December 15, 1950. A 

 deficiency in rainfall during the years in which these experiments 

 were conducted (table 1) made it necessary to irrigate the plots 

 before planting, usually in March. This is a common practice 

 among growers during years of light rainfall. The effect of the 

 treatments on the plant stand was determined by counting the 

 plants in each row before harvesting. 



