790 PRINCIPLES OF SOIL MICROBIOLOGY 



soil reaction. In the case of acid soils, there is a decided stimulating 

 effect as a result of application of lime, due also to a change in the 

 physical condition of the soil which results in making it a more favor- 

 able medium for the growth of bacteria. 



Ramann and associates 92 have shown in 1899 that bacteria predomi- 

 nate in alkaline and neutral soils, while in acid soils, fungi are more 

 predominant and may be even greatly in excess of the bacteria, 

 especially in acid peat soils. Treatment of soil with fertilizers, such 

 as ammonium sulfate, acid phosphate, sulfur, which tend to leave the 

 soil reaction acid, will tend to increase the number of fungi in the 

 soil and decrease the number of bacteria, especially when there is not 

 sufficient lime to neutralize the acid. A definite increase in the num- 

 ber of bacteria, as a result of addition of lime to acid soils, has been 

 observed repeatedly. 93 It was concluded that small applications of 

 CaC0 3 to acid soils are more effective, as a rule, than large applications 

 in stimulating bacterial activities; the stimulating effect was obtained, 

 however, only after the neutral point has been reached, as shown by 

 the Veitch method. This is not necessarily true for all soils, since in 

 the case of some acid soils a decided stimulating effect of lime upon 

 the numbers of bacteria is found even if the pll is not above 6.3. 

 Peat soils, which are usually acid in reaction, are characterized by a 

 high content of fungi and low content of actinomyces; 94 among the 

 bacteria, the butyric acid organisms predominate. 



MgC0 3 exerts a similar effect. The addition of CaO and MgO 

 resulted in a reduction in the carbon dioxide formation until the oxides 

 were all carbonated; then there was an increase, as in the case of the 

 carbonates. CaS0 4 seems to have no appreciable influence on bac- 

 terial activities in the soil. 94a When 0.5 gram CaO and 0.75 gram of 



92 Ramann, E., Remele, E., Schellhorn, and Krause, M. Anzahl und Bedeu- 

 tung der niederen Organismen in Wald- und Moosboden. Ztschr. Forst. u. 

 Jagdwes., 31: 577-606. 1899. 



93 Fischer, H. Uber den Einflusz des Kalkes auf die Bakterien eines Bodens. 

 Landw. Vers. Sta., 70: 335. 1909; Bear, F. E. A correlation between bac- 

 terial activity and lime requirement of soils. Soil Sci., 4: 433-462. 1917; 

 Hutchinson, H. B., and McLennan, K. Studies in the lime requirements of 

 certain soils. Jour. Agr. Sci., 7: 75-105. 1915. 



94 Ritter, G. A. Beitrage zur Kenntnis der niederen pflanzlichen Organismen, 

 besonders der Bakterien, von Hoch- und Niederungsmooren, in floristischer, 

 morphologischer und physiologischer Beziehung. Centrbl. Bakt. II, 34: 577- 

 666. 1912. 



94a See also Cubbon, M. H. Calcium sulfate as a soil amendment. Cornell 

 Univ. Agr. Exp. Sta. Mem. 97. 1926. 



