SOIL MICROBIOLOGICAL EQUILIBRIUM 



745 



True partial sterilization has been obtained only with the easily 

 volatile or removable antiseptics. Non-removable substances have a 

 lasting effect upon the flora, stimulating only a few species, without 

 bringing about, however, a considerable gain in ammonia or nitrate. 

 Larger doses of these chemicals may even suppress microbiological 

 activities. 19 The influence of the concentration of the antiseptic is 

 given in table 83. 



It is sufficient to mention, among the volatile antiseptics, toluol, 

 carbon bisulfide and chloroform. Concentrations of 1 to 4 per cent 

 of the disinfectant are allowed to act upon the soil for 12 to 48 hours; 

 the soil is then aerated so that the disinfectant may evaporate. Among 

 the non-volatile antiseptics, it is sufficient to mention phenol, cresol 



TABLE 83 

 Influence of toluene upon soil microorganisms and their activities 



C = ciliates; A = amoebae; F = flagellates. 



(m/10), cresyllic acid, calcium oxide, various metallic salts, like arsenic 

 compounds. Some of these, like the phenols, are decomposed in course 

 of time by various bacteria; CaO is soon carbonated; others, like the 

 arsenic oxide, may persist for some time in the soil. The intensity of 

 partial sterilization shades off gradually from the powerful non-volatile 

 antiseptics, through cresol (m/50) and formaldehyde, to the more or 

 less potent volatile antiseptics, until finally a hardly noticeable effect 

 is obtained, as in the case of merely spreading out the soil in a thin 

 layer. 19 



The use of heat as an agent of partial sterilization. Franke 23 observed 



23 Franke, B. Ueber den Einfluss, welchen das Sterilisieren des Erdbodens auf 

 die Pflanzenentwicklung ausubt. Ber. deut. bot. gesell. Generalsammlungsheft., 

 6: 87-97. 1888. 



