116 



BULLETIN No. 145 



[April, 



TABLE 21. ^-PRECIPITATED Matiere Noire; CARBON, NITROGEN AND PHOSPHO- 

 RUS IN THE PRECIPITATED Matiere Noire: RESULTS EXPRESSED AS 



POUNDS IN Two MILLION POUNDS OK DRY SOIL 

 (Soil first acid-extracted before treatment with ammonia) 



Phosphorus-nitrogen ratio == i 121.7 

 Nitrogen-carbon ratio i 19.5 

 Phosphorus-carbon ratio 1 1205 



Table 22 summarizes the results reported in Tables 20 and 21. 

 Of the total dissolved matiere noire only 50 percent was precipi- 

 tated. Again the greater part of the carbon and nitrogen remain 

 in the mother liquor. Only 44.5 percent of the carbon and 42.9 

 percent of the nitrogen were precipitated while but 8.7 percent of 

 the phosphorus was precipitated. 



TABLE 22. Matiere Noire; CARBON, NITROGEN AND PHOSPHORUS PRECIPI- 

 TATED FROM AMMONIACAL SOLUTION BY HYDROCHLORIC ACID: RESULTS 

 EXPRESSED AS PERCENT OF TOTAL SOLUBLE IN AMMONIA 

 (Soil first acid-extracted before treatment with ammonia) 



Again, the question regarding the source of the phosphorus 

 remaining in solution arises. It will be seen that 55.6 percent of 

 the soluble carbon and 58.1 percent of the soluble nitrogen also re- 

 main in solution. Attention should be called to the fact that when 

 the original soil was treated direct with ammonia, without previ- 

 ous extraction with hydrochloric acid, under conditions where the 

 maximum amount of inorganic phosphorus should be dissolved, 

 only 238 pounds of phosphorus per two million pounds of soil 

 were obtained : yet, after the soil had been treated with hydro- 

 chloric acid to remove the calcium, under conditions where the 

 minimum amount of inorganic phosphorus would be dissolved by 

 ammonia, 516 pounds of phosphorus per two million pounds of 

 soil were obtained. The difference between these two numbers, 

 278 pounds, unquestionably represents phosphorus which must have 

 been derived from organic sources. Now, since only 55 pounds of 

 phosphorus is precipitated with the matiere noire by hydrochloric 

 acid, it would appear that the organic phosphorus associated with 

 the precipitated mattere noire is only a very small part of the or- 

 ganic phosphorus present in the soil. 



