| Washington. | Montana. | |||||||
|---|---|---|---|---|---|---|---|---|
| Bunch grass Ritzville Ridge. | Bunch grass Selah Valley, Rolling Upland. | Judith Gap. | Near Bozeman Allen’s Ranch. | |||||
| Number of Sample | 46 | 37 | 371 | 387 | ||||
| Chemical Analysis of Fine Earth. | ||||||||
| Insoluble matter | 76.71 | 82.00 | 77.18 | 81.69 | 74.17 | 78.80 | 67.28 | 73.83 |
| Soluble silica | 5.28 | 4.59 | 4.61 | 6.54 | ||||
| Potash (K₂O) | .72 | .62 | 1.07 | 1.20 | ||||
| Soda (Na₂O) | .09 | .24 | .16 | .21 | ||||
| Lime (CaO) | 1.04 | 1.32 | .71 | 2.92 | ||||
| Magnesia (MgO) | .94 | .92 | 1.16 | 1.44 | ||||
| Br. ox. of Manganese (Mn₃O₄) | .05 | .05 | .97 | .62 | ||||
| Peroxid of Iron(Fe₂O₃) | 5.14 | 5.62 | 4.20 | 4.63 | ||||
| Alumina (Al₂O₃) | 5.74 | 5.24 | 7.08 | 8.09 | ||||
| Phosphoric acid (P₂O₅) | .16 | .13 | .12 | .18 | ||||
| Sulfuric acid (SO₃) | .01 | .05 | .02 | .01 | ||||
| Carbonic acid (CO₂) | 1.76 | |||||||
| Water and organic matter | 4.58 | 3.52 | 6.54 | 5.37 | ||||
| Total | 100.48 | 99.37 | 99.94 | 99.69 | ||||
| Humus | .90 | .48 | ||||||
| “ Ash | .42 | .32 | ||||||
| Hygroscopic Moisture | 5.60 | 4.84 | 9.77 | 10.37 | ||||
| absorbed at°C | 15 | 15 | 15 | 15 | ||||
Soils of the Humid Region.—Taking a view, first, of the table showing the soils of the humid region, it appears that the change of vegetation from walnut and hickory to the short-leaved pine bears no visible relation to the increase or decrease of potash or phosphoric acid, but is plainly governed mainly by the amount of lime present. Where the short-leaved pine prevails the soil is almost always either neutral or shows the alkaline reaction in the course of half an hour; but where the long-leaved pine predominates the soil has almost always an acid reaction. The latter is also usually found in bottoms in which the loblolly pine (P. taeda) prevails, and where, although the soil may show a fair proportion of lime in the analysis, it does not exist in the form of carbonate.
The examples here given are from lands not derived from, or underlaid by, limestone formations. Where the latter exist the percentage of lime is usually materially increased; as it is also in the lowlands or bottoms when compared with adjacent uplands ([see above, chapter 10, p. 162]; [chapter 18, p. 331]); as well as in the delta lands of rivers.
Soils of the Arid Region.—Even a cursory comparison of the soils of the arid regions of the Pacific slope with those of the humid, as given in the above tables, shows some striking points of difference. The most obvious is the uniformly high percentage of lime, and usually also of magnesia, in the arid soils, and that quite independently of underlying formations, calcareous or otherwise. This occurs despite the fact that while limestone formations are very prevalent east of the Rocky Mountains, they are quite scarce west of the same. The red (Laramie) sandstones of Wyoming, the slates of the foothills of the Sierra Nevada, the clay shales, granites and eruptives of the Coast Ranges of California, Oregon and Washington, and the varied black rocks of the great lava sheet of the Pacific Northwest, all alike produce soils of high lime content as compared with Eastern soils not derived from calcareous formations. This fact has already been referred to, but is more fully illustrated in the table below.
Aside from the lime-content, however, it will be noted in the preceding table that the potash-content of the arid soils is on the average considerably higher than in those of the humid region. In fact it is hard to find west of the Rocky Mountains (except where high elevation causes a humid climate) any soils as poor in potash as are many of the commonly cultivated lands of the Eastern United States.
Other ingredients do not show such marked differences from the purely chemical standpoint: yet, as will be shown below, the forms in which silica and alumina occur are also not inconsiderably modified.
General Comparison of Soils from the Arid and Humid Regions of the United States.[126]—In order to verify the conclusions just mentioned upon the broadest basis possible, the following table has been compiled from all available sources; partly published, partly in manuscript only, having remained in the writer’s hands since the cessation of the Northern Transcontinental Survey, prosecuted from 1880 to 1883, under the auspices of the Northern Pacific Railroad, in Washington and Montana. The published data are derived partly from the records of State surveys, partly from the soil work connected with the Tenth Census; partly also from those of Experiment Stations. In most cases it has of course been necessary to restrict the comparison to such analyses as have been made by substantially identical methods, for reasons already given; but in the cases of some states from which numerous analyses made by the Kedzie method, adopted by the Association of Official Chemists, were available, the average has been given but the name of the state starred, to indicate that the percentages, excepting phosphoric acid, are lower than they would be if made by the method adopted by the writer, particularly as regards potash. The adoption of the one-millimeter mesh for the fine-earth sieve instead of the half-millimeter size also creates an unfortunate and ineliminable discrepancy.
In order to exhibit clearly the influence of climate as distinct from other local conditions, it was also necessary to eliminate, in both the arid and humid regions, the soils directly derived from, or connected with calcareous formations; such as the prairies of the Southwestern States, the Bluegrass region of Kentucky, etc. This rule having been applied impartially to the soils of both climatic regions, it can hardly be questioned that the conclusions flowing from a discussion of the results of the comparison are entitled to as much weight as are those of any comparison based on large numbers of observations made, not with reference to the special point under consideration, but with a practical object of which the governing conditions were more or less uncertain, and required to be ascertained by a process of elimination.
The table gives, first, the averages for each ingredient for each of the states represented, the number of analyses from which the averages are derived being given in each case. These averages are given separately for the states of the humid and the arid regions respectively; and at the base of each group the grand average is shown in two forms. The first gives the figures as derived from the aggregate number of soil analyses in each great group, being 696 for the humid, 178 for the transition region and 573 for the arid, divided into the totals resulting from the summation of each ingredient for the whole 696, 178 and 573, respectively.
The second form is that in which the soils of each state are considered as representative of the general character of such state, as the result of intentional selection; such as actually occurred in the cases of those included in the census work of 1880. The figures given here are therefore the result of a summation of the state averages as such, and of their division by the number of states represented.