264 FUMIGATION METHODS 



produce a death atmosphere than will be needed in a 

 soil of much greater depth. In soils of the same 

 character and condition the amount needed will be 

 proportional to the permeable depth of the soil. In 

 heavy, compact soils increase the number of injections 

 and diminish the dose; in light, deep, permeable soils 

 decrease the number of holes and increase the dose. 



In field experiments with the grape, using plain 

 carbon bisulphid in quite fresh soil, vines withstood 

 105 c. c. of carbon bisulphid, nearly 4.4 ounces, 

 divided equally among three holes placed about 16 

 inches from the base of the vine and at a depth of about 

 20 inches; but 180 c. c. , 7^ ounces, proved fatal to 

 the vines. In warmer, drier, more shallow soil a dose 

 of 90 c. c. per vine, similarly placed, proved fatal. 

 After considerable rain, when the ground was quite 

 wet, a vine withstood 260 c. c. of carbon bisulphid, 

 and some vines are said to have withstood 400 c. c. 

 The treatment should never be applied for some time 

 after plowing or cultivating, as a firm, compact, moist 

 surface is much more favorable to the retention of the 

 vapor. For the same reason about fifteen days should 

 be allowed after treatment before cultivation is re- 

 sumed. If the soil is either very wet or dry, treatment 

 should be withheld. To be in the most favorable con- 

 dition for treatment, the soil should be quite moist and 

 moderately permeable, with a firm, even surface, well 

 compacted by rain and having a depth of at least eight 

 inches. 



The extent of diffusion of the vapor determines the 

 distance apart at which the injections must be made to 

 reach all parts of 'the soil evenly and effectively. This 



