100 BULLETIN No. 145 [April, 



In a later article (42) he showed that very little water soluble 

 phosphorous existed in the soil under consideration, but that dry- 

 ing 1 at 7o-8o rendered over 50 percent of the total phosphorus 

 soluble in water. 



Snyder (36) reported results of a confirmative nature regard- 

 ing the phosphorus associated with the humus in virgin and cul- 

 tivated soils. 



L,a.ter he (37,41) studied the product obtained by the conver- 

 sion of known substances, under known condition, into humus. 

 The ash of the mailer e noire obtained from this material contained 

 phosphorus, among other substances, and according to Snyder : 

 "There is every indication that these elements are in organic com- 

 bination with the carbon, hydrogen and oxygen of the humus." 

 As regards the question whether or not the humus united with the 

 inorganic phosphorus of the soil, he concluded that his experi- 

 mental evidence showed that such union did take place. 



Nannes (49) found that a well decomposed peat soil contained 

 0.166 percent phosphorus. He found that 0.057 percent of phos- 

 phorus was extracted with the matiere noire. When the ammonia- 

 cal solution of the matiere noire was treated with hydrochloric acid, 

 0.039 percent of the phosphorus was found in the organic precipi- 

 tate. He also attempted to isolate a definite organic phosphorus 

 compound and he believed that he detected the presence of lecithin 

 and chlorophyllan. 



Ladd (43) found in a study of eight samples of different soil 

 that an average of 41 percent of the phosphorus was associated 

 with the extracted matiere noire; the variation, however, was 

 from 10 percent to 90 percent. 



In a later article (44) he showed that as the humus of the soil 

 increased the phosphorus associated with the extracted matiere 

 noire also increased. From the fact that the organic precipitate, 

 formed by neutralizing the ammoniacal extract, contained the phos- 

 phorus he concluded that it existed in the soil in organic combina- 

 tion, but just what the relationship was not clear. 



Emmerling (52) believed that there were four forms of phos- 

 phorus in the soil, one of which was phosphorus in organic com- 

 bination. 



Rimbach (53) found 6.15 percent P2 65 in the ash of the 

 matiere noire which was precipitated from the ammoniacal solu- 

 tion by the addition of gypsum and magnesium sulfate. 



Nagaoka (57) found that ignition of the soil for fifteen min- 

 utes at a faint red heat materially increased the availability of the 

 phosphorus. He attributed this action to the destruction of the 

 humophosphates. 



