96 



BULLETIN No. 145 



[April, 



TABLE 2. PERCENTAGE OF TOTAL HUMIC, AMIDO, AMID AND AMMONIACAL 



NITROGEN IN HUMUS 



This did not account for all of the nitrogen present and so the 

 question arises in what form does the remainder exist? 



D'Utra (70) found that the humic nitrogen showed wide vari- 

 ations. 



Hilgard (71) reported the average humic nitrogen of 466 

 samples of soil from the humid regions as 5.45 percent, while the 

 average of 313 samples of soil from the arid section was 15.87 

 percent. Later (73) he found that the average humic nitrogen for 

 696 samples of humid soil was 5.00 percent, while that of 573 

 samples of arid soil was 15.23 percent. It must be remembered, 

 however, that the total quantity of nitrogen of the two regions is 

 in the inverse order. The total nitrogen of the uplands and low- 

 lands of California for example, is o.ioi percent and o.ioi per- 

 cent respectively, while the total nitrogen of the ordinary brown 

 silt loam soils of the corn belt in Illinois varies from 0.218 percent 

 to 0.337 percent. 



3. PHOSPHORUS IN SOILS 



The phosphorus of the soil may exist in the inorganic and 

 organic condition. The greater part is in the inorganic form with 

 an unknown amount in the organic state. The form and amount 

 of the organic phosphorus is uncertain, and, indeed it has been 

 questioned, especially during recent years, whether or not organic 

 phosphorus occurred in the soil to any appreciable extent. 



Mulder (i), as early as 1844, noted that the organic material 

 was not readily freed from phosphorus. 



The work of Thenard, Schutzenber (5, 6, 7) showed that union 

 may take place between various forms of artificial humus and phos- 

 phates under certain conditions and indicated that combination may 

 possibly take place in the soil between organic carbon and inorganic 

 phosphorus. 



Detmer (9) in the preparation of his "pure humic" acid, noted 



