VARIATION IN THE CHEMICAL COMPOSITION OF 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 in 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 
hi each province, and in the Great Plains with a variation of 0.11 
to 0.08, the Eiver 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. 
S0 3 . 
Memphis silt loam: 
1 
Per cent. 
81.13 
80.18 
91.39 
93.29 
94.50 
95.54 
92.87 
95.51 
90.22 
90. 90 
91.57 
91.17 
Percent. 
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 
Percent. 
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. 
Per cent. 
0.08 
.10 
.06 
.06 
.06 
.05 
.04 
.04 
.05 
.04 
.09 
.04 
Per cent. 
0-03 
2 
.03 
Cahaha 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 
