TRANSFORMATION OF MINERALS IN THE SOIL 



655 



In the case of the bone meal, the solubility of the phosphate was found 

 to depend on the fineness of division, amount and composition of fat 

 and nitrogen in the keratin and collagen. The decomposition of organic 

 matter in the soil is thus found to influence to a large extent the process 

 of rendering insoluble soil phosphorus available. 33 The presence of 

 calcium carbonate represses the solubility of the phosphate. 



The activities of the soil microorganisms, however, do not always 

 result in an increase of soluble phosphates, but may often even lead to 

 an actual diminution. 34 This takes place especially when a large 

 amount of energy bearing materials is added to the soil without a 

 corresponding addition of soluble phosphates. The available energy 

 stimulates the activities of various soil microorganisms, the synthe- 



TABLE 72 

 Influence of soil sterilization upon the activities of microorganisms and transfor?na- 



tion of phosphorus 



Upper figure found at beginning, lower at end of experiment. 



sizing processes of which result in a disappearance of the soluble phos- 

 phates in the soil. The actual amount of available phosphorus in the 

 soil was found to be a result of the sum total of the activities of the 

 microbial soil population which includes acid formation, secondary 

 reactions, and the synthesizing activities. Soil sterilized in the auto- 

 clave was reinoculated with pure cultures of bacteria or with soil sus- 



33 Krober, E. TJber das Loslichwerden der Phosphorsaure aus wasserunlcis- 

 lichen Verbindungen unter der Einwirkung von Bakterien und Hefen. Jour. 

 Landw., 57: 5-80. 1909; see also Koch, A., and Krober, E. Fuhlings landw. 

 Ztg., 55: 225-235. 1906. 



34 Sewerin, S. A. Die Mobilisierung der Phosphors;'iure des Bodens unter 

 dem Einflusz der Lebenstiitigkeit der Bakterien. Centrbl. Bakt. II, 28: 561- 

 580. 1910; 32: 498-520. 1912; Viestnik Bakteriol.-Agron. Stan. (Russian), 

 No. 21: 53-83. 1914. 



