VARIATION IN THE CHEMICAL COMPOSITION OP SOILS. 



13 



It should be borne in mind in this connection that soil provinces 

 may include soils derived from very different materials under very 

 diverse climatic conditions, and the number of samples is far too small 

 to permit any but the most general conclusions . 



The least variation is found hi the Great Plains and Glacial and 

 Loessial provinces, and the greatest in the Piedmont Plateau, and wide 

 variation in potash and soda is usually accompanied by wide varia- 

 tion in lime and magnesia. Phosphoric acid is remarkably uniform 

 in each province, and in the Great Plains with a variation of 0.11 

 to 0.08, the River Flood Plains 0.06 to 0.05, and the Limestone 

 Valleys 0.19 to 0.15 per cent the variation is not as great as might be 

 obtained in duplicate analyses of the same sample. Therefore, so far 

 as each of these provinces is represented by these samples, they may 

 be said to be uniform in phosphoric-acid content. 



VARIATION IN SOILS OF THE SAME TYPE. 



In this series of analyses few types are represented by more than 

 one sample, but comparing in some cases sandy loams with fine sandy 

 loams, the variation in major constituents in soils of the same or 

 approximate textures is shown in Table 6: 



Table 6. — Variation in chemical composition of samples of the same type or of types of 



approximate textures. 



Type. 



Si0 2 . 



Fe 2 3 . 



AI2O3. 



CaO. 



MgO. 



K 2 0. 



Na 2 0. 



P2O5. 



SO„. 



Memphis silt loam: 

 1 



Percent. 

 81.13 

 80.18 



91.39 

 93.29 



94.50 

 95.54 

 92.87 



95.51 

 90.22 



90.90 

 91.57 

 91. 17 



Per cent. 

 2.92 

 3.05 



.97 



.78 



.83 



.62 



1.17 



.68 

 1.52 



3.02 

 3.00 

 1.31 



Per cent. 

 8.52 

 8.48 



3.72 

 2.45 



2.07 

 1.70 

 2.75 



1.70 

 4.26 



2.59 

 2.78 

 3.65 



Per cent. 



0.31 



.27 



.21 

 .15 



.39 

 .06 

 .03 



.12 

 .06 



.11 



.04 



Trace. 



Per cent. 



0.39 



.45 



.09 

 .01 



.09 

 Trace. 

 Trace. 



Trace. 

 .01 



.09 



.03 



Trace. 



Per cent. 

 1.78 

 1.84 



.90 

 .45 



.10 

 .06 

 .05 



.16 

 .12 



.28 

 .10 

 .12 



Percent. 



0.52 



.72 



.12 

 .03 



.11 



.18 

 .01 



.04 

 .14 



Trace. 

 Trace. 

 Trace. 



Percent. 

 0.08 



.10 



.06 

 .06 



.06 

 .05 

 .04 



.04 

 .05 



.04 

 .09 

 .04 



Per cent. 

 0.03 



2 



.03 



Cahaba fine and 

 very fine sandy 

 loam: 

 1 



.06 



2 



.10 



Norfolk sandy and 

 fine sandy loam: 

 1 



.07 



2 



.03 



3 



.05 



Ruston fine sandy 

 loam: 

 1 



.23 



2 



.04 



Susquehanna fine 

 sandy loam: 

 1 



.07 



2... .... 



.08 



3 



.08 







It will be observed that the two samples of Memphis silt loam taken 

 a few miles apart in the same State are so nearly alike in composition 

 that they could very well be considered duplicates of the same sample, 

 and the same is true, perhaps to a less degree, of two samples of 

 Susquehanna fine sandy loam, No. 1 and No. 2, taken in Texas and 

 Mississippi, respectively. 



On the other hand, samples No. 2 and No. 3 of Susquehanna fine 

 sandy loam differ considerably in iron and alumina, and the samples 



