520 SOILS: PROPERTIES AND MANAGEMENT 



necessarily accepting all of Gedroiz's explanation of the 

 phenomenon, there can be little doubt that lack of basicity 

 is a factor in the availability of raw rock phosphates in 

 some soils. 



439. Influence of fermenting organic matter. There 

 has been great difference of opinion among investigators 

 as to the effect of fermentation of organic matter on the 

 availability of the phosphorus of tricalcium phosphate. 

 The contention that the availability is increased probably 

 originated with Stoklasa, 1 the results of whose experi- 

 ments with bone meal indicated that the availability is 

 increased by fermentation. A large number of experi- 

 ments have been conducted with raw rock phosphate 

 composted with stable manure, among which may be 

 mentioned those by Hartwell and Pember 2 and also by 

 Tottingham and Hoffman 3 who in carefully conducted 

 experiments failed to find that the availability of the raw 

 phosphate was increased by fermentation with stable 

 manure. Opposing results have also been obtained, how- 

 ever, and the evidence is somewhat conflicting. Krober, 4 

 who thinks that the action of bacteria is due to the acids 

 they produce, explains the contradictions in the various 



1 Stoklasa, J., Duchacek, F., and Pitra, J. Ueber den Ein- 

 fluss der Bakterien auf die Knochenzersetzung. Centrlb. f. 

 Bakt., II, Band 6, Seite 526-535, 554-558. 1900. 



2 Hartwell, B. L., and Pember, F. R. The effect of cow dung 

 on the availability of rock phosphate. Rhode Island Agr. 

 Exp. Sta., Bui. 151. 1912. 



3 Tottingham, W. E., and Hoffman, C. The Nature of the 

 Changes in Solubility and Availability of Phosphorus in Fer- 

 menting Mixtures. Wisconsin Agr. Exp. Sta., Research Bui. 

 29. 1913. 



4 Krober, E. Ueber das Loslichwerden der Phosphorsaure 

 aus Wasserunloslichen Verbindungen unter der Einwirkung 

 von Bakterien und Hefen. Jour. f. Landw., Band 57, Seite 

 5-80. 1909-1910. 



