314 ILLINOIS STATE ACADEMY OF SCIENCE 



excessively supplied with lime do not respond very well 

 to the application of phosphates. This well known fact 

 among soil workers seems to justify the procedure here 

 adopted. 



In time, the biological activities of these soils will also 

 add to the modification of their soil solution, but this 

 phase does not enter into the realm of the present study. 



The comparative work was done on soils of different 

 geological and morphological formations. Prairie soils 

 were represented by three soils of brown silt loam, two 

 of clay loam, and one each of drab clay loam, brown gray 

 silt loam of tight clay, and brown sandy loam. Timber 

 soils were represented by one sample each of the yellow 

 gray silt loam on gravel, yellow silt loam (eroded) and 

 yellow gray sandy loam. Terrace soils were represented 

 by brown sandy loam. Mixed loam was used as a bottom 

 land type formed along rivers; deep peat was a repre- 

 sentative of swamp lands. 



In each soil type the soils of three different depths 

 were used for the comparative tests with the phosphatic 

 fertilizers: (1) the plowed layer of 6 2/3 inches in depth, 



(2) the second layer from 6 2/3 inches to 20 inches, and 



(3) the layer from 20 to 40 inches. The second and the 

 third layers, of course, differ from the first one in their 

 physical and chemical properties, and the descriptive 

 name of soils for each layer is given here in order to 

 facilitate interpretation of the presented data. All soils 

 in this experiment were ordinary stock samples collected 

 in Champaign county for the soil survey analyses. 



These fourteen soils of three layers each, or forty-two 

 soil samples in all, were treated with either Tennessee 

 rock phosphate or double acid phosphate in such amounts 

 that in each case 4 mgs. of phosphorus were applied for 

 25 grams of mineral soil and for 12.5 gms. of peat of the 

 first two layers. The results presented in Table 2 show 

 the percent of applied phosphorus that was extracted 

 with nitric acid fifth normal. In each case the amount 

 of phosphorus extracted from the untreated soil was sub- 

 tracted from the amount of phosphorus extracted from 

 the treated soil. It constitutes a net gain due to the 

 treatment, and it assumes that the amount of soil phos- 



