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BULLETIN No. 145 



(April, 



obtained by the autoclave method but it is probably more nearly 

 correct since it is difficult to conceive how the treatment in the 

 autoclave would render any inorganic phosphorus soluble which 

 would not be rendered soluble by ignition while the work of Leav- 

 itt and LeClerc (81, 82) would indicate that ignition might render 

 some of the organic phosphorus insoluble in cold hydrochloric acid 

 of any strength. 



The calculation method shows that 423 pounds of phosphorus 

 per two millions of the surface soil are in organic combination: 

 the ammoniacal extraction method shows 504 pounds of organic 

 phosphorus and the ignition method shows 543 pounds, while 



TABLE 24. PHOSPHORUS SOLUBLE IN TWELVE PERCENT HYDROCHLORIC ACID: 

 RESULTS EXPRESSED AS POUNDS IN Two MILLION POUNDS OF SOIL 



TABLE 25. PHOSPHORUS SOLUBLE IN TWELVE PERCENT HYDROCHLORIC ACID: 

 RESULTS EXPRESSED AS POUNDS IN Two MILLION POUNDS OF SOIL 



Schmoeger's method shows that there are 607 pounds of organic 

 phosphorus. The calculation method is, therefore, very conserva- 

 tive in nature and it can be safely stated that at least that much 

 phosphorus is in organic combination. Table 26 gives the sum- 

 marized results of the organic phosphorus obtained by the several 

 methods. 



TABLE 26. TOTAL PHOSPHORUS AND ORGANIC PHOSPHORUS BY SEVERAL 



METHODS 



