AUTHORS REFERRED TO.

[Note.—In cases where no special credit is given in this volume for investigations made or data given from the Southwestern States and the Pacific Coast, these should be understood as work done, mostly under the writers direction, or by himself and assistants, in connections with the geological surveys of Mississippi and Louisiana, as well as the Tenth Census of the United States, by Drs. Eugene A. Smith and R. H. Loughridge; the chemical work for the Pacific Northwest, under the auspices of the Northern Transcontinental Survey, by M. E. Jaffa and Geo. E. Colby; that in California, at the Experiment Station, by the latter two, Dr. R. H. Loughridge, and temporary assistants. It would be impossible to segregate, without excessive prolixity, the credit to be assigned to each of these participants.]

Printed in the United States of America.

Footnotes:

[1] “The Soil Analyses of the Geological Surveys of Kentucky and Arkansas.” S. W. Johnson in Am. Jour. Sci., Sept. 1861.

[2] U. S. Geol. Survey, Professional Paper No. 14, p. 108.

[3] A trifling amount of chlorin is found oxidized in the form of sodium perchlorate, in the nitre deposits of Chile.

[4] See Rocks, Rock-weathering, and Soils, page 246; also paper on Domes and Dome Structure, by G. K. Gilbert, in Bulletins of the Geol. Society Am., Vol. 15, pp. 29-36.

[5] Collected by Dr. W. E. Ritter of the University of California.

[6] The term “overplaced,” used for such soils in late memoirs of the U. S. Geological Survey, is at least superfluous, in view of the perfectly understood term already in general use, and does not seem to commend itself for adoption by any special or superior fitness; nor does the suggestion of Shaler (The Origin and Nature of Soils, 12th Rep. U. S. Geol. Survey) to include the colluvial soils within the alluvial class, commend itself either from a theoretical or practical point of view, since but few useful generalizations can apply to both classes.

[7] Geikie, “Text-book of Geology,” 3d ed.

[8] Owing to the universal presence of water (H₂O) in air as well as in soils, it is usual and convenient to speak of carbonic dioxid (CO₂) gas when so occurring as carbonic acid (H₂CO₃), of which it produces the effects (CO₂ + H₂O = H₂CO₃).

[9] See Chapter 18.

[10] The increase of solvent power on feldspar when carbonated instead of distilled water is used, was well exemplified in an experiment made by Headden (Bull. 65, Color. Exp’t Sta., p. 29), who allowed pure distilled and carbonated water respectively to act on fresh but finely pulverized feldspar, with frequent shaking, for five days. The distilled water dissolved .0081 gram, the carbonated water, .0723 gram of solids, or nearly nine times as much as the distilled water. Both residues gave strong reactions for potash with platinic chlorid.

[11] Rivers of North America, p. 80.

[12] The correctness of Letheby’s analyses has been disputed, partly because of their disagreement with former analyses in the very high amount of lime, partly because of the high potash-content in the Low-Nile water. The lime content is, however, confirmed by the partial analyses made by Mathey in 1887, which gives an average of 44.1 for the year, while the older analyses, made in Europe, of transported water gave only half as much. Letheby working on the spot was doubtless more nearly right in this respect. His figure for potash in the “Low-Nile” water agrees with former determinations, but that in the “High-Nile” is approached only by that in the Dwina water. It may be suspected that the soda is too low and potash too high in this analysis.

[13] In some cases the soluble salts originate in rocks impregnated with salts from marine lagoons or landlocked lakes, or directly from their evaporation residues. But this is the exception rather than the rule.

[14] A zeolitic mass, at first gelatinous and then becoming granular-crystalline is frequently observed oozing from the lower surface of newly made concrete reservoir dams: just as we find similar oozes consolidated into natrolite crusts in the crevices of natural sandstones.

[15] T. M. Reade (in his treatise on Chemical Denudation in Relation to Geological Time) calculates that 143.5 tons of lime carbonate are annually removed by solution from each square mile of land in England and Wales, and that the average amount thus removed annually from each square mile of the earth’s surface is about fifty tons.

[16] Bull. No. 1, U. S. Dept. Agr. Veg. Path. and Physiol. Investig.

[17] This term was first employed by Th. Schloesing, in communications to the French Academy of Sciences, and reported in the Comptes Rendus of that body; first in 1870. Unaware of Schloesing’s work, the writer began a full investigation of the subject of mechanical soil analysis in 1871, and published the results in 1873 (Am. Jour. Sci., Oct. 1873). Up to that time the limited resources of the library of the University of Mississippi had not given him an opportunity to see Schloesing’s publication. The two independent investigations, though conducted on somewhat different lines, gave of course practically the same results, and complement each other.

[18] There is still some discussion as to the chemical identity of colloidal clay with Kaolinite; but the objections are not convincing.

[19] It has of late been attempted to extend the meaning of this word to the behavior of all powders when wetted with water. But the adhesive plasticity of clay stands almost alone, in that (aside from contraction) it preserves in drying the form into which it may have been molded while wet, even when struck, whereas other powdery substances similarly treated at once collapse back into the original powder. The exclusive use of clay in modeling offers the typical example of plasticity as generally understood. The addition of any powdery substance, however fine, diminishes the plasticity of clay.

[20] American Journal of Science, 2d Ser., Vol. 43, p. 357.

[21] Williams (Forsch. Agr. Phys. Vol. 18, p. 225 ff.) claims that the diameter of the minutest clay particles is one-thousandth of a millimeter, their form being that of scales showing continual (Brownian) motion in water. He maintains that the plasticity of clay is due to this minute size, and this view has gained wide acceptance in late works on the subject. But this assumption cannot be maintained in the face of the fact that nothing like the adhesive plasticity of clay can be attained even by the finest powders of other substances, least of all by those having the closest mineralogical resemblance to kaolinite, such as graphite and talc. Above all, the most persistent trituration with water utterly falls to restore plasticity to clay once baked so as to expel its water of hydration, although the fineness of the particles is thereby not only not diminished, but actually increased, by contraction in heating. No powders however fine can replace the functions of clay in soils, viz. the maintenance of floccules, and tilth dependent thereupon; and they distinctly impair the plasticity of clay. The fine “slickens” of quartz mills merely render soils containing them more close and impervious, and more difficult to flocculate. Even gelatinous masses like hydrated ferric and aluminic oxids fail to replace clay in its adhesive functions.

[22] Rep. Conn. Agr. Expt. Stn., 1886, 1887.

[23] And soda.

[24] This fact emphasizes the impossibility of explaining the plasticity and adhesiveness of clay simply as a function of fineness of grain.

[25] The figure given of this elutriator in Bulletin No. 24, on physical soil analysis, published by the U. S. Bureau of Soils, shows as the receiver a bottle entirely too low to insure the complete retention of the sediments by settling. The receiving bottle should not be less than twelve inches high and five inches wide.

[26] Convenient stands for this purpose, used by the writer since 1872, may be cut from L-shaped moldings of wood, such as can be readily ordered from any planing mill. The vials can be cemented, wired or tied.

[27] Bauxite is not only the most abundant of the three hydrates of alumina known to occur naturally, but also stands nearly midway between the two others in its water content, viz., a little over 25%; that of diaspore being nearly 15%, gibbsite about 35%.

[28] The Mechanical Composition of Wind Deposits, Bull. No. 1, Augustana Library Publications; 1898.

[29] This remarkable soil seems to have been derived from the finest “slickens” of the hydraulic gold mines.

[30] King, Physics of Agriculture, p. 116, ff.

[31] The word crumbs, which is generally understood as meaning a relatively large, loose aggregate, seems preferable to the word kernels, suggested for the same by King (Physics of the Soil, p. 110). Kernels are understood to be bodies rather more solid than the surrounding mass, and do not convey the idea of loose aggregates. The word “Krümelstructur” (crumb-structure), adopted by Wollny for this phenomenon, has both fitness and priority in its favor.

[32] Wollny (Forsch. Vol. 20, p. 13 ff., 1897) records similarly high shrinkages in his experiments.

[33] A totally different kind of “hog-wallows,” occurring in California and the arid region generally, have been described in a previous chapter under the head of Aeolian soils ([See chapt. 1, p. 9]).

[34] In driving a light carriage over the land represented by No. 643 above, after a light rain, the wheels gathered up so much soil within a hundred yards as to render it necessary to stop and chop it off the tires by means of a hatchet. This is a common experience in the black prairie lands of Texas.

[35] Schübler (Grundsätzed. Agrikulturchemie, 1838) ascribes the crumbling of calcareous clay soils to the difference in the contraction of calcareous sand and the clay substance. But it is doubtless more directly connected with the flocculation of the latter by lime.

[36] The antiseptic properties of sour humus are well exemplified in the perfect state of preservation in which the remains of animals, wood implements, etc., are found in bogs into which they have sunk in prehistoric times.

[37] See Müller, Natürliche Humusformen.

[38] Reports of the Rhode Island Exp’t Station, 1895, and ff.

[39] Wollny, Zersetzung der Organischen Stoffe, pp. 242, 243.

[40] Peat pulverized and extracted with alcohol and ether to remove resinous substances.

[41] Peat pulverized and extracted with alcohol and ether to remove resinous substances.

[42] Data recalculated, omitting ash.

[43] Detmer, Landw. Versuchst., Vol. 14, 1871.

[44] A striking illustration of this is afforded by Naegeli’s experiment of enclosing several loaves of bread in a loosely closed tin-box. After eighteen months there remained only seventeen per cent of air-dry mouldy matter, totally destitute of starch.

[45] Abstract in Ann. de la Science Agronomique, Tome 2, 1887.

[46] Bull. No. 70 Minn. Exp’t Station, 1905.

[47] The humus determinations thus made, which include nearly all those made by German chemists, give the humus-content from 40 to 50% too high. The French determinations are mostly made by the method of Grandeau.

[48] The decrease of humus from wheat culture in the soils of Minnesota and North Dakota has been studied by H. Snyder and E. F. Ladd, respectively. In the prairie lands of the latter State the total organic matter in the first six inches of soil ranges from 15 to as much as 26%, and the humus alone from 4 to 7.8%.

[49] Precipitation with an excess of acid does not greatly change the results.

[50] In California soils this is mostly silica soluble in carbonate of soda.

[51] Hilgard and Jaffa. On the Nitrogen-content of Soil-humus in the Humid and Arid regions. Rep. Cal. Exp’t Station for 1892-4; Agric. Science, April, 1894; Wollny’s Forsch. Geb. Agr. Phys., 1894.

[52] Introduced only for comparison of the nitrogen percentage in Humus and not included in the average.

[53] Bull. No. 53, Minn. Exp’t Station, p. 12, Chem. of Soils and Fertilizers, p. 94.

[54] The figures for cow manure are so far out of range with any others thus far observed, that it seems reasonable to suppose that they are influenced by unchanged substances present in the excreta.

[55] Bull., S. Dakota Station, Nos. 24-32, 35, 47.

[56] The mode of statement in the paper is not always quite clear as to the manner in which the averages given were calculated. It must be remembered that these data refer to cubic centimeters of soil, or about twice the amount (1 gram) used by European observers.

[57] Uber die Pilzsymbcose der Leguminosen, Berlin, 1890.

[58] Original figure from drawing by O. Butler, Asst. in Agr. Dep’t Univ. of California.

[59] “Living together” beneficially; in contradistinction to parasitism, which is injurious to the host plant.

[60] It is asserted by some observers that the root-bacilli producing differently-shaped excrescences upon different legumes are distinct species; but this view is not sustained by the experiments of Nobbe and Hiltner, and seems intrinsically improbable.

[61] Bull. Ala. Exp’t Station, No. 96, 1898.

[62] Kosticheff, Formation and Properties of Humus; in abstract Jour. Chem. Soc., 1891, p. 611.

[63] See Merrill, Rocks and Rock weathering.

[64] Shaler (Origin and Nature of Soils; 12th Rept. U. S. Geol. Survey, p. 311) says: “Annual plants cannot in their brief period of growth push their roots more than six to twelve inches below their root-crowns”—a generalization measurably true for the humid region only. According to F. J. Alway, the roots of cereals penetrate to 5-7 feet in Saskatchewan, also.

[65] See “Studien über die natürlichen Humusformen,” by Dr. P. E. Müller.

[66] Excepting only the water-solutions of certain salts, among which common salt, kainit and nitrate of soda are of agricultural interest. Common salt may increase the capillary rise to the extent of more than five per cent.

[67] A heat unit, or “calorie,” is the amount of heat required to raise the temperature of a unit-weight (pound, kilogram, or gram) of water one thermometric degree. According to the unit-weight and thermometric scale used, the figures will vary, but in this text the basis is understood to be kilograms and the centigrade scale.

[68] “Water and Forest,” January, 1905. “The Use of Water,” by S. Fortier.

[69] See Wollny’s experiments, Forsch. Agr. Phys. Vol. 20, p. 58.

[70] It should be understood that it is by no means easy to insure full saturation in any considerable volume of air.

It has generally been considered sufficient to cover with water the bottom of the space in which absorption was to occur. The writer found that in order to insure uniform results, it was necessary to cover the entire inner surface of the vessel with wet blotting paper, and even then to exclude carefully all circulation of air by padding the joints with such paper. When only the bottom of the box was covered, samples placed at different levels above the water surface gave discordant results. It was also observed that whenever the thickness of the soil layer exceeded about one millimeter, a long time was required for full saturation; during which inevitable changes of temperature would bring about a deposition of dew on the soil, greatly exaggerating the absorptive coefficient.

In the chamber used at the California station for soil saturation, dimensions 12 × 18 × 19 inches high, the same soil was exposed on a shelf close to the surface of the water, another midway up, a third near the lower surface of the cover; liquid water being in the bottom of the chamber, and the rest covered with wet blotters. It was found that despite these precautions, the lowest soil layer absorbed in the same time as much as ¾% more than the uppermost one.

[71] The partial saturation to a definite extent was effected by means of solutions of calcium chlorid of different degrees of concentration, according to the determinations of Wüllner (Pogg. Ann.). These solutions were placed in a wide, flat dish, over which a layer of soil 1 mm. in thickness was exposed, all being covered with a bell glass lined inside with the same solution, so as to insure equal saturation.

[72] E. A. Mitscherlich (Bodenkunde für Land-und Forstwirthe, p. 156 et al.) claims that all determinations of soil hygroscopicity thus far made are grossly incorrect on account of the dew liable to be condensed on the soil layer from fully saturated air, as the result of slight changes of temperature. He therefore would have all such determination made either in an air-vacuum, or over a 10% solution of sulfuric acid.

Such dew-formation, however, cannot happen to any appreciable extent under the conditions maintained in the writer’s work, viz, absorption within a thick-walled (two-inch) wooden box of the dimensions given above, and sunk in the ground in a cellar in which the temperature varies only a few tenths of a degree during 24 hours. The soil layer of one millimeter thickness being put down in the morning, the 7 hour absorption period falls at the time of slightly rising temperature, as an additional precaution against dew-deposition. Mitscherlich fails, moreover, to show that this source of error produces any wide or serious discrepancies except under such long absorption periods as he finds it necessary to use because of the great thickness of his soil layers. It is doubtful whether the limits of errors in soil sampling do not greatly exceed any of those involved in the writer’s method, and whether such accuracy as is attempted by Mitscherlich is of any practical significance.

[73] Simple as this operation appears to be, it is found to be by no means easy to expel with certainty every small air bubble without resorting to means which would destroy the natural condition of the soil; such as boiling, or the use of the air-pump. These determinations cannot therefore lay claim to great accuracy.

[74] The ascent is of course most rapid, in the large tubes almost instantaneous, when the capillary space is entirely clear; but in the complex system of connected air spaces in soils, the curved paths and the friction obstruct the movement.

[75] I. e., uniform between the narrow limits given.

[76] Ad. Mayer (Agriculturchemie 2, p. 141) designates this minimum content of liquid water as the “absolute” water capacity of the same; but it is not obvious wherein this factor is better entitled to this name than would be the maximum (see Wollny’s Forsch., 1892, p. 1.). M. Whitney (Rep. Proceedings Ass’n Agr. Coll. & Exp’t St’ns, Nov. 1904) gives as a new observation the fact that in soils approaching the drought condition water “does not obey the ordinary physical laws as we recognize them in capillarity.” This evidently refers simply to the well-known phenomenon mentioned above.

[77] This figure represents only a temporary condition; the full height of 46 inches was not reached until the 195th day.

[78] Hall (The Soil, p. 66) gives for the minima in the case of soils examined by him the following figures: coarse sandy soil, 22.2, light loam, 35.4, stiff clay, 45.6, sandy peat, 52.8. These figures are very much higher than for apparently similar materials used by the writer, and the differences exceed those between the maxima given for the same. This discrepancy I am unable to account for.

[79] Physics of Agriculture, p. 135.

[80] Rept. Cal. Expt. Sta. 1897-08, pp. 65-96.

[81] The quiet seepage from the banks and beds of streams plays a much more important part in the increase of volume of flow than is commonly supposed, because unperceived save by measurement of the tributaries and comparison with the main streams. This is especially true of the drainage in the arid region, where the deep and pervious soils favor diffuse seepage as against definite spring flow.

[82] Toumey (Yearbook U. S. Dep’t Agr. 1903) states that in the San Bernardino mountains in southern California, the first rainfall (in December) was absorbed to the extent of 95% in forested areas, against only 60% in the non-forested; but that later, after the soil had been partially saturated, 60% only was absorbed in the forested land, against 5% in the non-forested. While it is generally admitted that forests diminish the runoff, Rafter (Relation of Rainfall to Runoff, U. S. Geol. Survey Paper, No. 80, p. 53) contends that in New York State the reverse is true.

[83] Open Range and Irrigation Farming. R. H Forbes, in Forester, Nos. 7, 9, 1902.

[84] This effect is well illustrated by the behavior of a dry brick laid upon a wet sponge. It will quickly absorb all the liquid moisture contained in the latter, while the sponge will be wholly unable to take any moisture from a fully-soaked brick.

[85] Rep’t Calif. Exp’t Station for 1898 to 1901, p. 165.

[86] The exact record of these observations was unfortunately destroyed by fire; the soil was a heavy clay, and it took ten days before the water disappeared from the lowest hole.

[87] In contradistinction to other levels or “streams” of water which may usually be found lower down, separated from the first water by some impervious stratum of clay, hardpan or rock, and very commonly under sufficient pressure to rise somewhat higher than the point at which it was struck, owing to connection with higher-lying sources of supply. When such pressure is sufficient to cause an overflow at the surface of the ground, we have “Artesian” water as commonly understood.

[88] Physics of Agriculture, p. 270.

[89] Only a general outline of the principles of this subject is given in this volume; special works must be consulted for working details. Among these the volume by King on “Irrigation and Drainage” gives probably the most comprehensive presentation of the subject for both humid and arid climates. Also bulletins of the U. S. Dep’t of Agriculture.

[90] Published by permission of the Department.

[91] Such tests can be readily made by any one, by digging a pit to four or five feet depth, and supplying water to a shallow basin dug into the surface 8 to 12 inches distant from the vertical wall of the pit. The descent of the water is then readily observed on the vertical side of the pit nearest to the water basin. Preliminary tests with soil probe ([see chap. 10, p. 177]).

[92] [See below, chap. 17].

[93] Bull. No. 21, Bureau of Soils; also circular No. 10, ibid.

[94] Bull. Ariz. Exp’t Sta. No. 44.

[95] Bull. Arizona Exp’t Station Nos. 2, 38.

[96] Progress Report on Coöperative Irrigations in Calif.; Cir. No. 56, Office Exp’t Stations.

[97] Rep. Calif. Expt. Sta. for 1897-98, p. 65.

[98] In many cases this decrease of salinity is probably due to a slow influx of fresh water from landward; but very often it cannot be thus explained.

[99] Journal für praktische Chemie, Vol. 98, p. 167.

[100] The normal composition of atmospheric air is given on [p. 16, chap. 2].

[101] A striking case in point is the regular wind which in summer blows through the “Golden Gate,” a gap in the Coast Range connecting the Pacific Ocean directly with the great interior valley of California, along the bays of San Francisco, San Pablo, and Suisun. The great interior valley and adjacent mountain slopes becoming intensely heated during the rainless summer, the ascending air is replaced by a steady indraught from the sea, which is bordered by a belt of cold water causing fogs along the coast. The fogs are quickly dispelled on reaching the edge of the valley near the middle of its length; whence steady breezes blow northward and southward, up the valleys of the Sacramento and San Joaquin respectively. These winds, popularly often, but erroneously, called trade-winds, are really “monsoons” similar in their origin to those of India, which, when coming from the sea cause rains, but when from the heated land itself are hot and dry; as in the case of the sirocco of Italy and North Africa, the terral of Spain and the northers of California.

[102] This designation is popularly and incorrectly applied to the comparatively limited, but very violent and destructive rotary storms or whirlwinds which originate locally on the heated plains of the Middle West of the United States, and are almost always accompanied by violent electric phenomena. These should properly be called tornadoes. At sea such whirlwinds give rise to waterspouts, in deserts to sand storms.

[103] “The Evolution of Climates”; by Marsden Manson, July, 1903; also Amer. Geologist, Aug.-Oct. 1897.

[104] See Rept. of the U. S. Commissioner of Agriculture for 1878, pp. 486-488; Bull. Nos. 16 and 42, Wyoming Expt. Station; Bull. No. 150 Calif. Expt. Station; Bull. No. 51, Nevada Expt. Station; South Dakota Station Bulletins Nos. 40, 69, 70, 74; Kansas Expt. Station, Bulletin No. 102; New Mexico Expt. Station, Bulletin No. 18; Montana Expt. Station, Bulletin No. 30; and others.

[105] “Rocks and Soils,” pp. 175-189.

[106] The early work of Schübler on soil physics, published at Leipzig in 1838 under the title of “Grundsätze der Agrikulturchemie” and now almost inaccessible outside of old libraries, is remarkable as having anticipated very definitely much that has since been brought forward and elaborated anew. He is really the father of agricultural physics.

[107] Bull. 22, Bureau of Soils, U. S. Dept. of Agriculture.

[108] Whitney (Bull. 22, U. S. Bureau of Soils) claims on the basis of a large number of (three-minute) extractions of soils made with distilled water, that these solutions are essentially of the same composition in all soils; that all soils contain enough plant-food to produce crops indefinitely; and that the differences in production are due wholly to differences in the moisture supply, which he claims is, aside from climate, the only governing factor in plant growth. The tables of analytical results given in Bull. 22 fail to sustain the first contention; the second is pointedly contradicted both by practical experience, and by thousands of cumulative culture experiments made by scientific observers; the third fails with the second, except of course in so far as an adequate supply of moisture is known to be an absolute condition both of plant growth, and the utilization of plant-food. It is moreover well known that it is not water alone, but water impregnated more or less with humic and carbonic acids, that is the active solvent surrounding the plant root.

[109] [See Appendix B].

[110] The investigations of King (On the Influence of Soil Management upon the Water Soluble Salts in Soils and the Yield of Crops, Madison, 1903) show that from some soils at least, a sufficiency of plant-food ingredients for a season’s crop may be dissolved by distilled water alone, if the soil be repeatedly leached and dried at 110°. Whether such a supply can be expected under field conditions, remains to be tested.

[111] Vers. Stat. V. p. 207.

[112] Ibid. VI. p. 411.

[113] Proc. Ass’n Prom. Agr. Sci. 1904.

[114] Bulletin No. 22, Bureau of Soils, U. S. D. A.

[115] Ann. de la Sci. Agron., 2de série tome I, pp. 416-349; 1899.

[116] Zeitschr. Landw. Vers. Oesterr., 1901.

[117] While regretting to thus “secede” from the fellowship of his colleagues, the writer cannot but regret equally their voluntary decision to do over again, or lightly reject, all that had been done before in correlating soil-composition and plant-growth. He still thinks that it is idle to expect any unification, national or international, of methods of soil analysis based upon purely arbitrary prescriptions, unless previously shown to be definitely correlated with natural and cultural conditions; as is measurably the case with Dyer’s method.

[118] The Rio Grande and Colorado bottom soils contain amounts of lime carbonate largely in excess of requirements, 2 to 3% of that compound being all that is needed to insure all the advantageous effects of lime in any soil (see this chapter, page 367).

[119] Untersuchungen über die Bestimmung des Düngerbedürfnisses der Ackerböden und Kulturpflanzen, von G. Liebscher; Journal für Landwirtschaft 43 (1895), Nos. 1 & 2, pp. 48-216.

[120] La Valeur Agricole des Terres de Madagascar. Ann. de la Science Agronomique, 2’me série, tome 1, 1901.

[121] The Supply of Soil Nitrogen, Rep. Cal. Expt. Station, 1892-93, page 68; ibid., 1894-95, page 28; The Recognition of Nitrogen Hungriness in Soils, in Bull. 47, Div. of Chemistry, U.S. Department of Agriculture, 1895; Landw. Presse, No. 53, July 1885. See also for detailed data chapter 8, page 135.

[122] Calculated upon the true humus substance (matière noire), not by determining total (incl. unhumified) nitrogen in the soil.

[123] This statement appears contradictory of the observations of Schloesing upon the solubility of phosphoric acid in presence of lime carbonate (Am. Sci. Agron., tome 1, 1899), but the natural conditions seem to justify fully the above conclusion.

[124] See discussions of analyses of Mississippi soils in the Report on the Agriculture and Geology of Mississippi, 1860; same in Rep. On Cotton Production, Tenth Census, 1880, Vol. 5; also Appendix to the Report on the Experiment Stations of the University of California, 1890, p. 163.

[125] In the discussion in this chapter the “humid region” referred to is always that of the temperate zones, unless expressly otherwise stated. The most humid region of all—the tropics—is treated under a special head.

[126] Abstracted and revised from Bulletin No. 3, U. S. Weather Bureau, 1893.

[127] Bull. No. 1, Div. Veget. Physiol, and Plant Pathol. U. S. Dept. Agr.; et al.

[128] Loeb, Publications of the Spreckel’s Physiological Laboratory of the University of California, has shown a similar protective influence of the lime salts in sea-water, against the other salts, in the case of the lower marine organisms.

[129] “Black Soils;” Agric. Science, January, 1892.

[130] Bull. No. 18, Div. Vegetable Physiology and Plant Pathology; Bull. No. 1, Bureau of Plant Industry, U. S. Dept. of Agr.; Bull. College of Agriculture, Tokyo, Vol. 4, No. 5.

[131] Rep. Agr. and Geology of Mississippi, 1860, p. 360.

[132] Bull. Agr. Coll. Tokyo, Vol. V., Nos. 2 and 4.

[133] Ibid. Vol. 6.

[134] Looking at the details of the several states, we find that on the arid side Washington has a relatively low figure for soluble silica, which in the average, however, is overborne by the high figures for California and Montana. The explanation of this fact probably lies in the derivation of the majority of the Washington soils examined, from lake deposits brought down gradually from the humid region at the heads of the Columbia drainage, where sandy beds are very prevalent; while the country rock—the basaltic eruptives—are very basic, and moreover slow to disintegrate. In California and Montana the rocks are infinitely varied, and the general outcome of their weathering is plainly a predominance of complex hydrous silicates in the soils, as compared with humid regions.

[135] Analyses by R. H. Loughridge.

[136] Analyses by L. M. Tolman.

[137] Analyses by E. H. Lea.

[138] Analyses by R. H. Loughridge.

[139] Analyses by L. M. Tolman.

[140] Analyses by E. H. Lea.

[141] Report of the Tenth Census, Vols. 5 & 6; see especially the analyses of soils from Mississippi and Alabama. Also the Reports of the California Experiment Station.

[142] Excepting the relatively rare minerals of the Allophane, Kollyrite, and Miloshite group.

[143] Since any complex zeolite would contain less alumina than kaolinite, this assumption more than covers the possible zeolitic alumina.

[144] See for comparison the data given in vols. 5 and 6 of the report of the Tenth Census of the United States.

[145] Ann. Sci. Agronomique, tome 1, 1899.

[146] Landw. Presse, 1900, No. 52; ibid. 1901, Nos. 23 and 24.

[147] Bull. Univ. Tokyo, Vol. 6, No. 3. Production was diminished to less than one half when lime was used with bone meal, and actual assimilation of phosphoric acid to one fifth.

[148] [See table, chapter 19, p. 256].

[149] In the light alkali lands of the southern California Experiment Substation at Chino, the average content of water-soluble potash in ten acres amounts to the equivalent of 1,200 pounds of potash sulphate per acre. Outside of this the acid-soluble potash of the soil is .95%., equal to 38,000 pounds per acre-foot.

[150] Samoa Erkundung, by F. Wohltmann, Kolonial-Wirthsch. Komitee, Berlin, 1904.

[151] Wohltmann states that the hot extraction sometimes yielded as much as five times more than the cold; but no such case appears in his reports on Samoa and Kamerun.

[152] The numbers in brackets are determinations made after boiling with acid for one hour.

[153] Soil air-dry.

[154] The numbers in brackets are determinations made after boiling with acid for one hour.

[155] Annales de la Science Agronomique, tome 1er, 1901, fasicules 1, 2, 3.

[156] On the Composition of Indian Soils. Agr. Ledger, 1898, No. 2.

[157] Analysis by Voelcker.

[158] Analyses by Mann.

[159] That is to say, they now produce about 600 pounds, or 10 bushels of wheat per acre, as do the Rothamstead soils after fifty years’ exhaustive cultivation. Probably both have come down to the permanent level of production corresponding to the amount of plant-food made currently available each year by the fallowing process in originally very rich soils. The present product of cotton on the regur lands does not seem to be on record; judging by the wheat product it should not be over one hundred pounds of lint per acre.

[160] See Voelcker, Report on the Improvement of Indian Agriculture, 1892, p. 46, par. 60.

[161] Verhandlungen der Deutschen Physiologischen Gesellschaft in Berlin, December, 1892; North American Review, September, 1902.

[162] [See Chapter 2, p. 26].

[163] [See above, chapter 16, p. 294].

[164] See Chapter 23.

[165] Hilgard and Loughridge, Bulletin No. 128, California Experiment Station; Report California Experiment Station, 1894-95, p. 37; Bulletin No. 30, Office of Experiment Stations; Wollny’s Forsch. Geb. Agr. Phys., 1896.

[166] An abstract of the report of this commission is given in the Report of the California Experiment Station for 1890.

[167] See Agricultural Ledger, 1897, No. 13; ibid. 1901, No. 13.

[168] In this designation are included, in this volume, both the normal (mono-) carbonate and the two other compounds, the bi- or hydrocarbonate and the intermediate (so-called sesqui-) compound or trona; all of which are commonly present simultaneously, but in utterly indefinite relative proportions, varying from day to day and from inch to inch of depth, inasmuch as their continued existence depends upon the greater or less formation of carbonic acid in the soil, and the access of air. Hence their separate quantitative determination at any one time is of little practical interest. All naturally occurring carbonate of soda contains, and sometimes consists of, these “super-carbonates,” according to the greater or less exposure to air and solar heat. They are much milder in their action on plants than the monocarbonate, which unfortunately, in the nature of the case, always predominates near the surface, and thus injures the root-crown.

[169] A wholly different kind of “black alkali” exists in some regions, especially in the delta lands of the Colorado of the West and in the Pecos and Rio Grande country in New Mexico. In these cases the dark tint is due, not to a humic solution, but simply to moisture, which is tenaciously retained by the chlorids of calcium and magnesium impregnating the land, thus contrasting strongly with the gray tint of the general dry soil.

[170] Report of the California Exp’t. St’n. for 1892-94, p. 141.

[171] Proc. Am. Soc. Agr. Sci., 1888; ibid., 1890; Rep. Cal. Expt. Sta., 1890, p. 100; Ber. Berlin, Chem. Ges., 1893; Am. Jour. Sci., August 1896.

[172] Farmer’s Bull. No. 88, U. S. Dept. Agr., 1899.

[173] For a general statement and discussion of the physiological effects of saline solutions on plants, see chapter 26.

[174] [See p. 242, Chap. 13].

[175] Bull. 133, Cal. Expt. Sta., by R. H. Loughridge.

[176] Bulletins Nos. 128, 133 and 140, Calif. Expt. Station.

[177] The several columns of figures are independent of each other; the “total” alkali is not the summation for the three salts in the same line.

[178] Figures taken from Bulletin 169, Calif. Expt. Station, June, 1905.

[179] See Bulletin No. 16 of the Wyoming Experiment Station; also Bulletin Nos, 2 and 12 of the Division of Agrostology, and Farmers’ Bulletin No. 108, U. S. Department of Agriculture.

[180] Analyses made at the California station show 19.37 percent of ash in the air-dry matter of Australian saltbush. (See California Station Bulletin No. 105; E. S. R., vol. 6, p. 718). Analyses of Russian thistle have been reported showing over 20 per cent of ash in dry matter. (See Minnesota Sta. Bulletin No. 34; Iowa Sta. Bull. No. 26; E. S. R., vol. 6, pp. 552-553).

[181] It should be understood that the plants so referred to are exclusively the true grasses, recognized as such by every child, and not forage plants generally; which are sometimes so designated; not only by farmers, but by some authors who fail to appreciate the practical importance of the distinction, which makes it necessary that farmers should be taught to understand it.

[182] Report on Cotton Culture; 10th Census of the United States, vol. 5, pp. 23 to 34.

[183] The special object of this chapter as a whole has seemed to the writer to require a repetition of much that is already said in the preceding chapters.

[184] [See above, pp. 313 to 315, chapter 18].

[185] Such lists, so far as the State of Mississippi is concerned, may be found in the writer’s Report on the Agriculture and Geology of Mississippi, 1860. See also Plant Life of Alabama, by Charles Mohr.

[186] “A lime country is a rich country.”

[187] R. M. Harper, who has graphically described the vegetative features of the coastal plain of Georgia (Contr. from the Dep. of Bot. Colum. Univ. Nos. 192, 215, 216, 1902-05; also Bull. Torr. Bot. Club 29-32), claims the deciduous cypress of the wet pine-barrens and ponds therein, the vegetation of which greatly resembles that of the pine meadows of the Mississippi sea-coast, to be a distinct species, Taxodium imbricarium, the leaves of which are imbricated, instead of two-ranked and with spreading leaflets. He supports this distinction mainly by the differences in habit from the Louisiana swamp cypress, and the fact that the imbricated form occurs wholly on non-calcareous land, while the other is at home in the calcareous alluvial areas. The imbricated form has been observed and commented on before, as a mere ecological variation, and in the writer’s opinion this is all that can be claimed, in view of the much greater differences in the form of other trees, notably oaks, illustrated below, caused also by lime. There would, à fortiori, be reason for claiming at least three different species of post oak and black-jack (and two of willow oak), which differ not only in tree form but also in the form and number of leaf lobes, and yet can be traced into one another by innumerable transition forms. If new species are to be established on such grounds, it is hard to see where the variations manifestly due to environment are to come in.

[188] It is a matter of regret to the writer that owing to the long distance intervening and the difficulty of securing competent and sympathetic observers for such work, it has not been possible for him to secure photographs of the tree-forms here discussed. At the time his own observations were made, photography was practically unavailable as yet, and the figures given are therefore based upon sketches made at the time, and partly upon recollection. They represent types rather than definite individuals, which were however described when fresh in mind, in the Report on the Agriculture and Geology of Mississippi, 1860, pages 254 et seq.

[189] It has been already, and doubtless will be again and increasingly, attempted to make distinct “species” of these widely different forms of trees. But this is simply begging the question. Mere external diagnostic marks will not avail here; it would have to be shown that the seed of these different forms do not produce the other forms under changed conditions. Until this has been done, the number-less transition forms which he that runs may observe in the field, throw upon the species-makers the onus of proof of differences of specific value—if it be possible to define such value.

[190] Rep. of Geological Reconnaissance of Louisiana; New Orleans, 1873, p. 27.

[191] [See Chapter 2, p. 24].

[192] Hence perhaps the vernacular name “gumbo” for heavy, adhesive clay soils in the north central states; which may also, however, be derived from a comparison with the “gummy” pods of the cultivated okra or gumbo plant.

[193] See Plant Life of Alabama, by Charles Mohr, Vol. VI. Contr. U. S. Nat. Herb., U. S. Dep’t Agr.; Alabama Ed. of Same, Ala. Geol. Survey, 1901.

[194] See “Final Report of a Geological Reconnoisssance of Louisiana,” published by the New Orleans Academy of Science in 1871.

[195] In view of its specific designation and the reputed poverty of New England soils, this is rather unexpected.

[196] Essai de Phytostatique appliquée à la chaine du Jura et aux contrées voisines. 2 vols. 8vo. Berne, 1849.

[197] Annales de Chimie et de Physique, 4me série, tome 29; ibid. 5me série, Tome 2. Also, ibid, tome 18, 1879.

[198] Bull. de la Société Botanique de France, tome 26, 1879.

[199] Geographie botanique. Influence du terrain sur la vegetation. Baillère et Fils, Paris, 1881, 143 pp.

[200] Pflanzengeographie, p. 111 & ff.

[201] Report No. 71, U. S. Dep’t. of Agriculture, 1902.

[202] This plant grows with equal luxuriance in soils containing only 680 pounds of carbonates.

[203] For more details see chapters [3] and [4].

[204] This writer’s valuable “Boden Runde” (1905) unfortunately came to hand too late to be considered in this volume.

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