INORGANIC COMPOSITION OF SOME AMERICAN SOILS. 



15 



Table II. — Partial composition of soils analyzed by Failyer, Smith, and Wade. 



COASTAL PLAIN SERIES. 



Soil type and location. 



CaO. 



MgO. 



K 2 0. 



Per cent. 



Per cent. 



Per cent. 



0.12 



0.13 



0.79 



.13 



.19 



.60 



.24 



.10 



.79 



.07 



.29 



1.11 



.08 



.05 



.28 



.19 



.29 



.92 



.14 



.10 



.42 



p 2 o 5 



Collington sandy loam, New Jersey.. 



Norfolk sand, Maryland 



Norfolk loam, Maryland 



Lefinardtown loam, Maryland 



Orangeburg sandy loam, Alabama. . 



Crowley silt loam, Louisiana 



Orangeburg fine sandy loam, Texas . 



Per cent. 

 0.03 

 .06 

 .07 

 .03 

 .06 

 .14 

 .11 



SOILS DERIVED FROM LIMESTONES AND SHALES. 



Oswego silt loam, Kansas 



Hagerstown loam, Tennessee. 

 Hagerstown clay, Kentucky. . 

 Houston clay, Alabama 



0.40 



0.36 



1.24 



.40 



.56 



.77 



3.12 



1.54 



4.30 



28.02 



1.21 



1.01 



0.12 

 .12 

 .40 

 .59 



Soils formed from limestone may be low in lime, as is shown by the 

 Oswego silt loam and the Hagerstown loam in Table II and by Nos. 

 3 and 4 in Table I. 



During the process of formation and changes in the soil, manganese, 

 with one exception, appears to be concentrated in the surface layers. 

 This seems to be due to a difference in the solubility of the salts of 

 lower and higher states of oxidation. Solutions of reduced manganese 

 could move unchanged in the subsoil, but on coming near the sur- 

 face, where oxidizing conditions prevail, the manganese would be 

 precipitated as the nearly insoluble higher oxide. Plants might accu- 

 mulate certain elements selectively absorbed as food in the surface 

 soil, provided such elements were not soluble in atmospheric condi- 

 tions. Phosphorus has undergone a similar concentration, and it 

 would seem that in this case the larger part of the concentration was 

 effected by the selective absorption of this element by plants, the 

 plants yielding their phosphoric acid to the soil by decomposition 

 and this element being held in the surface soil in difficultly soluble 

 combinations with the ever present bases. 



The most striking differences in composition between the surface 

 soil and the subsoil is shown by the silica content. This difference 

 is greater in soils profoundly weathered and subject to erosion and 

 less in the glaciated soils. Complementary to this silica variation is 

 the variation in iron, aluminum, and, generally, titanium. It seems 

 that at the surface erosion has carried away the finer particles con- 

 taining large amounts of iron and aluminum and has left the larger 

 sand grains, consisting mostly of quartz, in the surface soil. Some 

 of the finer particles might have been driven into the subsoil by rain, 

 or by the movements incident to alternate wetting and drying, but 

 it would seem that by far the larger part of the concentration was 

 effected by surface wash. 



