jp/o] CARBON, PHOSPHORUS AND NITROGEN IN SOILS 121 



CONCLUSIONS 



1. The phosphorus-nitrogen ratio in the surface soil of the 

 brown silt loam soils is I 113.5 while the same ratio in the black 

 clay loam soils is i 111.4. 



2. Under normal conditions the nitrogen-carbon ratio of the 

 soil has a tendency to become narrower as the age of the organic 

 material increases : the ratio, however, never becomes narrower or 

 even equal to the ratio of the more common proteins contained in 

 the humus producing materials. 



3. The nitrogen-carbon ratios of the ordinary brown silt loam 

 soils of Illinois are 1:12.1, 1:11.5 and 1:8.9 m tne surface, sub- 

 surface, and subsoil respectively. 



The ratios in the black, clay loam soils are 1 111.7, 1 111.9 and 

 i :Q in the surface, subsurface, and subsoil respectively. 



4. The phosphorus-carbon ratio in the surface soil of the 

 brown silt loam is i :i65.2 while the ratio in the surface soil of the 

 black clay loam soils is 1 1163.6. 



5. 1^ calculation method for determining organic phosphorus 

 is very cwiservative in character and can be relied upon in drawing 

 broad general conclusions. 



6. The evaporation on the water bath of the ammoniacal so- 

 lution, in the preparation of the mailer e noire in quantity for analy- 

 sis, causes a hydrolysis of the organic phosphorus compounds. 



7. The determination of the phosphorus associated with the 

 precipitated matiere noire is not a quantitative method for the de- 

 termination of the total organic phosphorus of the soil. It should 

 be regarded only as a good qualitative evidence of the existence of 

 organic phosphorus in the soil. 



8. The contention of Fraps that, "There is no evidence that 

 the phosphoric acid in the nitrate is in organic combination" and 

 that, "It is" probably derived from the iron and aluminium phos- 

 phates" is entirely untenable. 



