

 110 



BULLETIN No. 145 



[April, 



TABI,E 14. II,:LINOIS SOILS: ORGANIC PHOSPHORUS; RATIOS OF CARBON TO 



PHOSPHORUS, NITROGEN TO PHOSPHORUS AND CARBON TO NITROGEN, 



FACTORS FOR CALCULATING THE ORGANIC PHOSPHORUS. 



(b) Subsoil (7" 40") 



The ordinary brown silt loam soils, as an average of 59 deter- 

 minations, gave the ratios of 1 1165.2 and i :i3-5 respectively. The 

 black clay loam soils, as an average of 25 calculations, gave the 

 ratios of 1 1163 and i :ii-4 respectively. The ratios in the surface 

 peaty soil, assuming all the phosphorus to be in the organic state, 

 are 1 1230 and 1 119.6. The ratios in the subsoil of the peaty soil 

 are somewhat wider, being i 1338 and 1 126.5 respectively. 



(c) FACTORS FOR CALCULATING ORGANIC PHOSPHORUS 



By means of the carbon-phosphorus ratios established as in- 

 dicated above, it is possible to develop factors for calculating the 

 amount of the organic phosphorus in the surface soil from the 

 total organic carbon. For example the carbon-phosphorus ratio, 

 1 1163, in the black clay loam soils means that for every part of 

 organic phosphorus there are 163 parts of carbon or for each part 

 of organic carbon there are 0.006113 P ai *ts of organic phosphorus. 

 Hence by multiplying the amount of organic carbon by the latter 

 number the amount of organic phosphorus may be obtained. 



The factors as developed will be found in the last column of 

 Table 14. It is hoped that they will be of value in drawing broad 

 general conclusions regarding organic phosphorus of the soil from 

 a number of analyses. The variations in the various samples con- 

 sidered in any single type are too great to permit the utilization of 

 the factors in isolated cases. 



