752 PRINCIPLES OF SOIL MICROBIOLOGY 



+ 6 grams glucose gave 7,215 milligrams of C0 2 in nineteen days 

 when treated with 170 grams of CSj, while the untreated soil gave 

 5,991 milligrams. Soil treated with heat or volatile antiseptics has a 

 much greater oxidizing power, as indicated by the oxygen absorption by 

 the soil. 52 



Stormer suggested that the disinfectants kill the larger soil organisms, 

 such as worms, insects, fungi, algae, protozoa; these are then decom- 

 posed by the surviving bacteria with the formation of ammonia. Bac- 

 terial development and ammonia accumulation are a result of this 

 decomposition. The total increase in ammonia nitrogen over the 

 untreated soil is not more than 3 to 4 mgm. of nitrogen per 100 grams 

 of soil; this quantity can be readily derived from the decomposed 

 organisms. Garden soils may be very rich in nematodes which often 

 do great damage to the crop. 53 These nematodes are destroyed by 

 the disinfectant. Among the injurious bacteria, which may also be 

 destroyed, are the nitrate and sulfate reducing forms. 



According to Stoklasa, 54 the increase in soil fertility due to treatment 

 with CS 2 , chloroform, benzol, or ether is due to the destruction of a 

 definite number of soil microorganisms; the surviving bacteria readily 

 break down the dead organisms, liberating phosphate and other ions, 

 which now become available for plant growth. It is to be noted that 

 among the organisms which develop in great abundance in partially 

 sterilized soils Clostridium pastorianum, the anaerobic nitrogen-fixing 

 organism, occupies a prominent place, occurring as 100,000 or more 

 per gram of soil. 55 



It thus became evident that the treatment of soil with antiseptics 

 is equivalent to nitrogen fertilization. It was suggested 56 that partial 

 sterilization of soil renders a number of undecomposed plant residues, 

 such as pectins and pentosans, more soluble; these are used as sources 



* 2 Darbishire, F. V., and Russell, E. J. Oxidation in soils and its relation to 

 productiveness. II. The influence of partial sterilization. Jour. Agr. Sci., 2: 

 305-326. 1908. 



63 Emmerich, R. W., Graf zu Leiningen, and Loew,~0. t)ber Bodensaubei- 

 ung. Centrbl. Bakt. II, 29: 668. 1911; 31: 466-477. 1911. 



64 Stoklasa, 1911 (p. 649). 



66 Truffaut, G., and Bezssonoff, N. Influence de la sterilisation partielle sur 

 la composition de la flore microbienne du sol. Compt. Rend. Acad. Sci., 170: 

 1278-9. 1920; 171: 268-270. 1920; 172: 1319-1323. 1921. 



56 Heinze, B. Einiges iiber den Schwefelkohlenstoff, dessen Wirkung auf 

 niedere pflanzliche Organismen, sowie seine Bedeutung fiir die Fruchtbarkeit 

 des Bodens. Centrbl. Bakt. II, 16: 329-357. 1906; 18: 56, 246, 462, 624, 790. 

 1907; Landw. Jahrb., 36: 418. 1907. 



