EFFECT OF NITRIFYING BACTERIA ON THE SOLU- 

 BILITY OF TRICALCIUM PHOSPHATE^ 

 By W. P. Kblley^ 



Professor of Agricultural Chemistry, Graduate School of Tropical Agriculture and 

 Citrus Experiment Station, University of California 



INTRODUCTION 



The solution of tricalciurn phosphate and the chemical changes through 

 which it passes in soils are subjects of special interest. The phosphorus 

 compounds of soils have been mainly derived from tricalcium phosphate, 

 and are relatively insoluble in water. A considerable part of the phos- 

 phorus of soils probably actually occurs as tricalcium phosphate. The 

 soluble phosphates of processed fertilizer also become relatively insoluble 

 soon after being mixed with soil, some of which may be converted into 

 tricalcium phosphate. In addition, tricalcium phosphate, in the form 

 of untreated rock phosphate, has been recommended as a fertilizer at 

 various times in the past and at present is being applied in considerable 

 amounts in different parts of America. 



While tricalcium phosphate is relatively insoluble in water, it is well 

 known that this substance is notably soluble in water saturated with 

 carbon dioxid. For this reason it has long been suspected that the 

 carbonic acid of soils promotes the solution of the phosphates present. 

 Likewise the increased fertilizing effect resulting from the application 

 of rock phosphate in conjunction with decaying organic matter has 

 commonly been assumed to be due to the solvent effects of the carbonic 

 acid, and possibly other organic acids, that are formed in the decom- 

 position of the organic matter. 



As a rule, however, investigators have not been able to detect any 

 increase in the solubility of rock phosphate when left in contact with 

 decaying organic matter. For example, Lupton ((5)^ McDowell (7), 

 Truog (9),Tottinghara and Hoffmann (8), and various European workers* 

 found, as a result of composting rock phosphate with various fermenting 

 mixtures, that in no case more than slight increases in the solubility of 

 the phosphate took place and in certain instances decreases in solubiUty 

 were noted. 



> Paper No. 45, University of California Graduate School of Tropical Agriculture and Citrus Experiment 

 Station, Riverside, Cal. 

 » Credit is due Mr. A. B. Cummins for assistance in this investigation. 

 ' Reference is made by number (italic) to " Literature cited," p. 685. 

 * A very complete bibliography of this subject is given by Lipman, McLean, and Lint (5). 



Journal of Agricultural Research, Vol. Xil, No. 10 



Washington. D. C. March n,' 1918 



n* ,, , KeyNo. Cal. 18 



(671) 



