560 ABSTRACTS 



To increase azofication, non-leguminous manures must remain longer 

 in the soil than leguminous in order to give time for considerable de- 

 composition to occur before a crop is grown to test the effects. — Z. N. 



Can Soil Be Sterilized without Radical Alteration? David A, Coleman, 



H. Clay Lint, and Nicholas Kopeloff. (Soil Science, 1916, 1, 259- 



274.) 



An effort was made to devise some method whereby soil might be 

 rendered sterile with a minimum amount of alteration. Four different 

 lines of experimentation were carried on: 1. The intermittent steri- 

 lization of soil by dry heat; 2. Various chemical substances used as soil 

 antiseptics; 3. Volatile antiseptics apphed in partial vacuum; and 4. 

 Volatile antiseptics applied under pressure at 80°C. 



Both moist and dry soils were sterilized at 82°C. for 1 hour on 1 to 5 

 successive days. Ammonia determinations were made after each heat- 

 ing, also bacterial counts on Lipman and Brown's synthetic agar. All 

 protozoa were killed at the first heating; species of PenicilUum and 

 Mucor persisted throughout. The numbers of bacteria in the moist 

 soil decreased from 47,750,000 per gram on the first day to 1,500 on the 

 last day while although there was an initial depression in numbers of 

 bacteria in the dry soil, an increase occurred on the first day, then a 

 gradual decrease only. This method of soil sterilization is decidedly 

 more efficacious in the sterilization of moist than of air-dry soil. It in- 

 creases the total solids in the soil about 46 per cent, which is only one 

 sixteenth as much as by the common method of steam sterilization. 

 Where the time element is of considerable importance this method is 

 undesirable. 



As soil antiseptics, were used 1 per cent (on the basis of 100 gm. of 

 air-dry soil) of ethyl alcohol, ethyl ether, toluene, carbon bisulfid, chloro- 

 form and hydrogen peroxid. Chloroform caused a decrease of 86 per 

 cent of the original bacterial content and caused the least alteration in 

 the chemical constitution of the soil; carbon bisulfid and toluene were 

 next in order. 



In addition to the first four volatile antiseptics named above, osmic 

 acid was used in the third method of sterilization. The antiseptic 

 vapor was allowed to remain in intimate contact with the soil for 1^ 

 hours for 3 successive days. Carbon bisulfid, toluene and ethyl alco- 

 hol, in order, caused a decrease of 99+ per cent of the original soil 

 flora, although their action is more efficient in air-dry soil. 



Carbon tetrachloride, carbon bisulfid, ethyl ether and chloroform 

 were used in the heat plus pressure method. They were used at a tem- 

 perature of 80°C. for 3 successive days upon moist and air-dry soil. 

 The decrease in bacterial flora, in general, approximated 98 per cent. 

 Carbon bisulfid was the only chemical which proved superior to the 

 check treatment; it developed a pressure of 20 pounds. Ethyl ether 

 which was least efficient developed only 6 pounds. A possible corre- 

 lation might be obtained between the pressure developed during treat- 

 ment and the effectiveness of the sterilizing agent. Carbon tetrachlor- 

 ide, which developed 5 pounds pressure is an exception. — Z. N. 



