PRINCIPLES AND PRACTICE
—OF—
AGRICULTURAL ANALYSIS.
A MANUAL FOR THE ESTIMATION OF SOILS, FERTILIZERS, AND AGRICULTURAL
PRODUCTS.
FOR THE USE OF ANALYSTS, TEACHERS, AND STUDENTS OF AGRICULTURAL
CHEMISTRY.
VOLUME I.
=SOILS.=
BY HARVEY W. WILEY,
CHEMIST OF THE U. S. DEPARTMENT OF AGRICULTURE.
EASTON, PA.,
CHEMICAL PUBLISHING CO.,
1894.
COPYRIGHT, 1895,
BY HARVEY W. WILEY.
PREFACE TO VOLUME FIRST.
In this volume I have endeavored to place in the hands of teachers and
students of Agricultural Analysis, and of analysts generally, the
principles which underlie the science and art of the analysis of soils
and the best approved methods of conducting it.
In the prosecution of the work I have drawn freely on the results of
experience in all countries, but especially in the matter of the
physical examinations of soils, of this country. Science is not
delimited by geographic lines, but an author is not to be blamed in
first considering favorably the work of the country in which he lives.
It is only when he can see nothing of good outside of its own boundaries
that he should be judged culpable. It has been my wish to give full
credit to those from whose work the subject-matter of this volume has
been largely taken. If, in any case, there has been neglect in this
matter, it has not been due to any desire on my part to bear the honors
which rightfully belong to another. With no wish to discriminate, where
so many favors have been extended, especial acknowledgments should be
made to Messrs. Hilgard, Osborne, Whitney, and Merrill, for assistance
in reading the manuscript of chapters relating to the origin of soils,
their physical properties, and mechanical analysis. With the wish that
this volume may prove of benefit to the workers for whom it was written
I offer it for their consideration.
H. W. WILEY.
WASHINGTON, D. C.,
Beginning of January, 1895.
TABLE OF CONTENTS OF VOLUME FIRST.
PART FIRST.
_Introduction_, pp. 1–27.—Definitions; Origin of soil; Chemical elements
in the soil; Atomic masses; Properties of the elements; Relative
abundance of the elements; Minerals occurring in rocks; Classification
of minerals.
_Rocks and Rock Decay_, pp. 28–43.—Types of rocks; Microscopical
Structure of Rocks; Composition of rocks; Color of rocks; Kinds of
rocks; Eruptive rocks.
_Origin of Soils_, pp. 43–63.—Decay of rocks; Effect of latitude on
decay; Action of water; Action of vegetable life; Action of worms and
bacteria; Action of air; Classification of soils; Qualities and kinds of
soils; Humus; Soil and subsoil; Authorities cited in part first.
PART SECOND.
_Taking Samples for Analysis_, pp. 65–86.—General principles; General
directions for sampling; Method of Hilgard; Official French method;
Caldwell’s, Wahnschaffe’s, Peligot’s, and Whitney’s methods; Samples for
moisture; Samples for permeability; Samples for staple crops; Method of
the Royal Agricultural Society; Method of Grandeau; Method of Official
Agricultural Chemists; Method of Lawes; Instruments for taking samples;
Principles of success in sampling.
_Treatment of Sample in the Laboratory_, pp. 87–93.—Preliminary
examination; Treatment of loose soils; Treatment of compact soils;
Miscellaneous methods; Authorities cited in part second.
PART THIRD.
_Physical Properties of Soils_, pp. 95–101.—The soil as a mass; Color of
soils; Odoriferous matters in soils; Specific gravity; Apparent specific
gravity.
_Relation of Soil to Heat_, pp. 102–103.—Sources of soil heat; Specific
heat; Absorption of solar heat.
_Determination of Specific Heat_, pp. 104–110.—General principles;
Method of Pfaundler; Variation of specific heat.
_Soil Thermometry_, pp. 111–115.—General principles; Frear’s method of
stating results; Method of Whitney and Marvin.
_Applications of Soil Thermometry_, pp. 115–116.—Absorption of heat;
Conductivity of soils for heat.
_Cohesion and Adhesion of Soils_, pp. 116–117.—Behavior of soil after
wetting; Methods of determining cohesion and adhesion; Adhesion of soil
to wood and iron.
_Absorption by Soils_, pp. 117–130.—General principles; Summary of data;
Cause of absorption; Deductions of Warington, Way, and Armsby; Selective
absorption of potash; Influence of surface area; Effect of removal of
organic matters; Importance of soil absorption; Methods of determining
absorption; Statement of results; Preparation of salts for absorption.
_Relations of Porosity to Soil Moisture_, pp. 131–150.—Definition of
porosity; Influence of drainage; Capacity of soil for moisture;
Determination of porosity; Whitney’s method; Relation of fine soil to
moisture; Wolff’s and Wahnschaffe’s method; Petermann’s method; Mayer’s
method; Volumetric determination; Wollny’s method; Heinrich’s method;
Effect of pressure on water capacity; Coefficient of evaporation;
Determination of capillary attraction; Inverse capillarity;
Determination of coefficient of evaporation; Wolff’s method; Water given
off in a water-free atmosphere; Porosity of soil for gases;
Determination of permeability in the field.
_Movement of Water Through Soils: Lysimetry_, pp. 151–170.—Porosity in
relation to water movement; Methods of water movement; Capillary
movement of water; Causes of water movement; Surface tension of
fertilizers; Methods of estimating surface tension; Preparation of soil
extracts; Lysimetry; Relative rate of flow of water through soils;
Measurement of rate of percolation; Authorities cited in part third.
PART FOURTH.
MECHANICAL ANALYSIS.
_The Flocculation of Soil Particles_, pp. 171–185.—Relation of
flocculation to mechanical analysis; Effect of potential of surface
particles; Destruction of floccules; Suspension of clay in water; effect
of chemical action; Theory of Barus; Physical explanation of subsidence;
Separation of soil into particles of standard size; Mechanical
separation; Sifting with water.
_Separation of Soil Particles by a Liquid_, pp. 185–207.—Classification
of methods of silt analysis; Methods depending on subsidence of soil
particles; Methods of Kühn, Knop, Wolff, Moore, Bennigsen, and Gasparin;
Method of Osborne; Schloesing’s method.
_Separation of Soil Particles by a Liquid in Motion_, pp.
207–247.—General principles; Nöbel’s Apparatus; Method of Dietrich;
Method of Masure; Method of Schöne; Mayer’s method; Osborne-Schöne
method; Statement of results; Berlin-Schöne method; Hilgard’s method;
Colloidal clay; Properties of pure clay; Separation of fine sediments;
Weighing sediments; Classification of results; Comparison of methods.
_Miscellaneous Determinations_, pp. 247–281.—Mechanical determination of
clay; Effect of boiling on clay; General conclusions; Distribution of
soil ingredients; Percentage of silt by classes; Interpretation of silt
analysis; Number of soil particles; Surface area of soil particles;
Logarithmic constants; Mineralogical examination of silt; Microscopical
examination; Petrographic microscope; Forms and dimensions of particles;
Silt classes; Crystal angles; Refractive index; Polarized light;
Staining silt particles; Cleavage of soil particles; Microchemical
examination of silt particles; Petrographic examination of silt
particles; Separation of silt particles by specific gravity; Separation
with a magnet; Color and transparency; Value of silt analyses;
Authorities cited in part fourth.
PART FIFTH.
_Estimation of Gases in Soils_, pp. 282–300.—Carbon dioxid; Aqueous
vapor; Maximum hygroscopic coefficient; Absorption of aqueous vapors;
Oxygen and air; General method of determining absorption; Special
methods; Diffusion of carbon dioxid; General conclusions; Authorities
cited in part fifth.
PART SIXTH.
_Chemical Analysis of Soils_, pp. 301–342.—Preliminary considerations;
Order of examination; Determination of water in soils; General
conclusions; Estimation of organic matter in soils; Estimation of humus;
Estimation of carbonates in arable soils.
_Digestion of Soils with Solvents_, pp. 342–352.—Treatment with water;
With water saturated with carbon dioxid; With water containing ammonium
chlorid; With water containing acetic acid; Treatment with citric acid;
With hydrochloric acid; With nitric acid; With hydrofluoric and
sulphuric acids.
_Determination of the Dissolved Matter_, pp. 352–367.—Methods of the
Official Agricultural Chemists; Hilgard’s methods; Belgian methods; Bulk
analysis.
_Special Methods of Soil Analysis_, pp. 367–428.—Determination of
potash; Potash soluble in concentrated acids; Soluble in dilute acids;
Estimation as platinochlorid; German Station methods; Raulin’s method;
Russian method; Italian method; Smith’s method; International method;
Dyer’s method; Estimation of total alkalies and alkaline earths; French
method for lime; Estimation of actual calcium carbonate; Estimation of
active calcareous matter; Russian method for lime; Assimilable lime;
German lime method; Estimation of magnesia; Estimation of manganese;
Estimation of iron; Estimation of phosphoric acid; Estimation of
sulfuric acid; Estimation of chlorin; Estimation of silica; Simultaneous
estimation of different elements; Estimation of kaolin in soils.
_Estimation of Nitrogen in Soils_, pp. 428–458.—Nature of nitrogenous
principles; Method of Official Agricultural Chemists; Hilgard’s method;
Moist combustion method of Müller; Soda-lime method; Treatment of soil
containing nitrates; Volumetric method with copper oxid; Estimation of
ammonia; Amid nitrogen; Volatile nitrogenous compounds; Late methods of
the Official Agricultural Chemists; Authorities cited in part sixth.
PART SEVENTH.
_Oxidized Nitrogen in Soils_, pp. 459–496.—Organic nitrogen; Nitric and
nitrous acids; Conditions of nitrification; Production of nitric and
nitrous acids; Production of ammonia; Order of oxidation; Occurrence of
nitrifying organisms; Nitrifying power of soils; Culture of nitrifying
organisms; Isolation of nitrous and nitric ferments; Classification of
nitrifying organisms; Sterilization; Thermostats for cultures;
Conclusions.
_Determination of Nitric and Nitrous Acids in Soils_, pp.
496–531.—Classification of methods; Extraction of nitric acid; The
nitric oxid process; Schloesing’s method; Warington’s method; Spiegel’s
method; Schulze-Tiemann method; DeKoninck’s method; Schmitt’s process;
Merits of the ferrous salt method; Mercury and sulfuric acid method;
Lunge’s nitrometer; Utility of the method; The indigo method.
_Determination of Nitric Nitrogen by Reduction to Ammonia_, pp.
531–542.—Classification of methods; Method of the Official Agricultural
Chemists; German method; Devarda’s method; Stoklassa’s process;
Sievert’s variation; Variation of the sodium-amalgam process; Schmitt’s
method; Process of Ulsch; Reduction by the electric current; Copper-zinc
and aluminum-mercury couples.
_Iodometric Estimation of Nitric Acid_, pp. 543–548.—Method of DeKoninck
and Nihoul; Method of Gooch and Gruener.
_Estimation of Nitric and Nitrous Acids by Colorimetric Comparison_, pp.
548–570.—Delicacy of the process; Hooker’s carbazol method;
Phenylsulfuric acid method; Estimation of nitric in presence of nitrous
acid; Metaphenylenediamin method for nitrous acid. Sulfanilic acid test;
Naphthylamin process; Use of starch as indicator; Method of Chabrier;
Ferrous salt method; Potassium ferrocyanid method; Collecting samples of
rain water.
_Determination of Free and Albuminoid Ammonia_, pp. 570–575.—Nessler
process; Ilosvay’s reagent; Authorities cited in part seventh.
PART EIGHTH.
_Special Examination of Waters_, pp. 576–583.—Total solid matter;
Estimation of chlorin; Estimation of carbon dioxid; Boric acid.
_Special Treatment of Muck Soils_, pp. 583–591.—Sampling; Water content;
Organic carbon and hydrogen; Total volatile matter; Estimation of
sulfur; Estimation of phosphoric acid; Estimation of humus; Special
study of soluble matters in muck.
_Unusual Constituents of Soil_, pp. 580–593.—Estimation of copper;
Estimation of lead; Estimation of zinc; Estimation of boron; Authorities
cited in part eighth. Index, pp. 594–607.
* * * * *
=CORRECTIONS.=—Page 112, second line from bottom, read “Fig. 14” instead
of “13.”
Page 158, insert “and determining soluble matters therein” after “flow”
in paragraph =172=, third line.
Page 468, paragraph =423=, read “calcium carbonate about 200
milligrams,” instead of “calcium carbonate, or gypsum fifty milligrams.”
Page 557, read “red-yellow” instead of “blue” in seventh line from
bottom.
ILLUSTRATIONS TO VOLUME FIRST.
Page.
Plate, figures 1–6. To face 29
Figure 7. Microscopic structure of sandstone 36
„ 8. Microstructure of crystalline limestone 39
„ 9. Microstructure of Gneiss 40
Plate, figure 10. View on the broad branch of Rock Creek, 48
Washington, D. C., to face
Figure 11. 82
„ 12. 84
„ 13. Regnault’s apparatus for determining the specific heat 105
of soils
„ 14. Soil thermometer 113
„ 15. Zalomanoff’s apparatus for determining absorption of 126
salts by soils
„ 16. Müller’s apparatus to show absorption of salts by 127
soils
Plate, figure 17. Capacity of the fine soil for holding moisture. 136
Method of Wolff modified by Wahnschaffe, to face
Figure 18. Fuelling’s apparatus 140
„ 19. Apparatus to show capillary attraction of soils for 145
water
Plate, figure 20. Apparatus for determining coefficient of 148
evaporation, to face
Figure 21. Method of Heinrich 150
„ 22. Method of Welitschowsky 162
„ 23. Ground plan and vertical section of lysimeters and 166
vaults showing position of the apparatus
Plate, figure 24. Deherain’s apparatus for collecting drainage 168
water, to face
Figure 25. Knop’s silt cylinder 190
„ 26. Siphon cylinder for silt analysis 191
„ 27. Bennigsen’s silt flasks 195
„ 28. Nöbel’s elutriator 208
„ 29. Dietrich’s elutriator 209
„ 30. Masure’s silt apparatus 211
„ 31. Schöne’s elutriator 212
„ 32. Schöne’s elutriator outflow tube 213
„ 33. Schöne’s elutriator, arrangement of apparatus 214
„ 34. Schöne’s apparatus for silt analysis, modified by 221
Mayer
„ 35. Hilgard’s churn elutriator 226
„ 36. Improved Schöne’s apparatus with relay 228
„ 37. 257
Plate, figure 38. To
face
264
„ figures 39–44. „
„ figures 45–50. „
„ figures 51–56. „
Figure 57. Machine for making mineral sections 267
„ 58. Thoulet’s separating apparatus 272
„ 59. Harada’s apparatus 275
„ 60. Brögger’s apparatus 276
„ 61. Apparatus of Wülfing 277
„ 62. Schloesing’s soil-tube for collecting gases 291
„ 63. Schloesing’s apparatus for collecting gases from soil 292
„ 64. Schloesing’s apparatus for determination of carbon 293
dioxid
„ 65. Knorr’s apparatus for the determination of carbon 338
dioxid
„ 66. Bernard’s calcimeter 339
„ 67. Smith’s muffle for decomposition of silicates 381
„ 68. Apparatus by Sachsse and Becker 401
Plate, figures 69 and 70. To face 480
Figure 71. Sterilizing oven 491
„ 72. Autoclave sterilizer 492
„ 73. Arnold’s sterilizer 493
„ 74. Lautenschläger’s thermostat 494
„ 75. Schloesing’s apparatus for nitric acid 501
„ 76. Warington’s apparatus for nitric acid 505
„ 77. Spiegel’s apparatus for nitric acid 509
„ 78. Schulze-Tiemann’s nitric acid apparatus 511
„ 79. DeKoninck’s apparatus 514
„ 80. End of delivery-tube 514
„ 81. Schmidt’s apparatus 516
„ 82. Lunge’s nitrometer 519
„ 83. Lunge’s improved apparatus 521
„ 84. Lunge’s analytic apparatus 523
„ 85. Stoklassa’s nitric acid apparatus 535
„ 86. Variation of the sodium amalgam process 537
„ 87. McGowan’s apparatus for the iodometric estimation of 544
nitric acid
„ 88. Apparatus of Gooch and Gruener 547
„ 89. Method of Chabrier 566
„ 90. Schaeffer’s nitrous acid method 568
„ 91. Retort for distilling ammonia 572
„ 92. Gooch’s apparatus for boric acid 581
„ 93. Apparatus for determining sulfur 587
PART FIRST.
INTRODUCTION.
=1. Definitions.=—The term soil, in its broadest sense, is used to
designate that portion of the surface of the earth which has resulted
from the disintegration of rocks and the decay of plants and animals,
and which is suited, under proper conditions of moisture and
temperature, to the growth of plants. It consists, therefore, chiefly of
mineral substances, together with some products of organic life, and of
certain living organisms whose activity may influence vegetable growth
either favorably or otherwise. The soil also holds varying quantities of
gaseous matter and of water, which are important factors in its
functions.
=2. Origin Of Soil.=—Agriculturally considered, the soil proper is the
older and more thoroughly disintegrated superficial layer of the earth,
which has been longest exposed to weathering and the influences of
organic life. It is usually from six to twelve inches, but occasionally
several feet in depth. The subsoil, which lies directly under this, is
not as a rule so thoroughly disintegrated, since it is protected in a
measure by the overlying soil. It usually contains less organic matter
than the soil. There is a freer circulation of air in the soil than in
the subsoil, and the metallic elements usually exist therein as higher
oxids. There is usually a notable difference in color between the soil
and subsoil, and frequently a very sharp color line separating the two.
Geologically considered, the soil is that portion of the earth’s crust
which has been more or less thoroughly disintegrated by weathering and
other forces from the original rock formations, or from the sedimentary
rocks, or from the unconsolidated sedimentary material. The soil has,
therefore, the same essential constitution as the general mass of the
earth, except that this débris has been subjected to the solvent action
of water and the influence of vegetable growth.
Preliminary to the proper understanding of the methods of the analysis
of soils, there should be some definite knowledge concerning the
composition of the earth’s crust, so that the analyst may understand
more thoroughly the origin and nature of the material he has to deal
with, and thereby be better equipped for his work.
=3. The Chemical Elements Present in the Soil.=—The chemical elements
present in the soil are naturally some or all of those which were
present in the original rocks. For analytical purposes relating to
agriculture, it is not necessary to take into account the rare elements
which may occur in the soil, but only those need be considered which are
present in some quantity and which enter as an important factor into
plant growth. Of the whole number of chemical elements less than twenty
are of any importance in soil analysis. These elements may be grouped
into two classes, the non-metals, and the metals as follows:
Non-metals. Metals.
Oxygen, Aluminum,
Silicon, Calcium,
Carbon, Magnesium,
Sulfur, Potassium,
Hydrogen, Sodium,
Chlorin, Iron,
Phosphorus, Manganese,
Nitrogen, Barium.
Fluorin,
Boron.
=4. Atomic Masses.=—For the purpose of facilitating the calculation of
results the latest revised table of atomic masses is given below. All
the known elements are included in this table for the convenience of
analysts who may have to study some of the rarer elements in the course
of their work.
This table represents the latest and most trustworthy results reduced
to a uniform basis of comparison with oxygen = 16 as starting point of
the system. No decimal places representing large uncertainties are
used. When values vary, with equal probability on both sides, so far
as our present knowledge goes, as in the case of cadmium (111.8 and
112.2), the mean value is given in the table.
TABLE OF ATOMIC MASSES OF
THE ELEMENTS.
Revised by F. W. Clarke,
Chief Chemist of the United
States Geological Survey, to
January 1st, 1894.
────────────┬───────┬───────
Name. │Symbol.│Atomic
│ │ mass.
────────────┼───────┼───────
Aluminum │Al │ 27
Antimony │Sb │ 120
Arsenic │As │ 75
Barium │Ba │ 137.43
Bismuth │Bi │ 208.9
Boron │B │ 11
Bromin │Br │ 79.95
Cadmium │Cd │ 112
Cesium │Cs │ 132.9
Calcium │Ca │ 40
Carbon │C │ 12
Cerium │Ce │ 140.2
Chlorin │Cl │ 35.45
Chromium │Cr │ 52.1
Cobalt │Co │ 59
Columbium[A]│Cb[Nb] │ 94
Copper │Cu │ 63.6
Erbium │Er │ 166.3
Fluorin │F │ 19
Gadolinium │Gd │ 156.1
Gallium │Ga │ 69
Germanium │Ge │ 72.3
Glucinum[B] │Gl[Be] │ 9
Gold │Au │ 197.3
Hydrogen │H │ 1.008
Indium │In │ 113.7
Iodin │I │ 126.85
Iridium │Ir │ 193.1
Iron │Fe │ 56
Lanthanum │La │ 138.2
Lead │Pb │ 206.95
Lithium │Li │ 7.02
Magnesium │Mg │ 24.3
Manganese │Mn │ 55
Mercury │Hg │ 200
Molybdenum │Mo │ 96
Neodymium │Nd │ 140.5
Nickel │Ni │ 58.7
Nitrogen │N │ 14.03
Osmium │Os │ 190.8
Oxygen[C] │O │ 16
Palladium │Pd │ 106.6
Phosphorus │P │ 31
Platinum │Pt │ 195
Potassium │K │ 39.11
Praseodymium│Pr │ 143.5
Rhodium │Rh │ 103
Rubidium │Rb │ 85.5
Ruthenium │Ru │ 101.6
Samarium │Sm │ 150
Scandium │Sc │ 44
Selenium │Se │ 79
Silicon │Si │ 28.4
Silver │Ag │ 107.92
Sodium │Na │ 23.05
Strontium │Sr │ 87.6
Sulfur │S │ 32.06
Tantalum │Ta │ 182.6
Tellurium │Te │ 125
Terbium │Tb │ 160.0
Thallium │Tl │ 204.18
Thorium │Th │ 232.6
Thulium │Tu │ 170.7
Tin │Sn │ 119
Titanium │Ti │ 48
Tungsten │W │ 184
Uranium │U │ 239.6
Vanadium │V │ 51.4
Ytterbium │Yb │ 173
Yttrium │Yt │ 89.1
Zinc │Zn │ 65.3
Zirconium │Zr │ 90.6
────────────┴───────┴───────
Footnote A:
Has priority over niobium.
Footnote B:
Has priority over beryllium.
Footnote C:
Standard or basis of the system.
PROPERTIES OF THE ELEMENTS.
Following is a brief description of the most important elements
occurring in the earth’s crust in respect of their relations to
agriculture.
=5. Oxygen= exists in the free gaseous state in the atmosphere of which
it constitutes about one-fifth by bulk, whilst in combination with other
elements it forms nearly half the weight of the solid earth, and
eight-ninths by weight of water. It enters into combination with all the
other elements, except fluorin, forming what are known as oxids, and
with many of the elements it unites in several proportions, forming
oxids of different composition. Combined with silicon, carbon, sulfur,
and phosphorus, it forms an essential part of the silicates, carbonates,
sulfates, and phosphates, most of which are very abundant and all of
which are very widely distributed in the earth’s crust. In this form it
is exceedingly stable and is rarely set free. With the exception of the
oxids of silicon these oxids seldom occur uncombined with the metals as
constituents of rocks or soils. The oxids of iron very commonly occur as
such in rocks and soils, and play a very important part in organic life.
The several oxids of iron very frequently determine the color of soils;
as the iron in a soil is more or less oxidized, or as it is exposed more
or less to access of air, the color of the soil changes. These oxids of
iron also play an important part in the absorption capacities of soils
for moisture and other physical conditions of soils, and also in the
oxidation of organic matters in the soil. Many organic substances, and
even the roots of growing plants when deprived of free access of air,
can readily secure oxygen from the iron oxid, thus reducing the iron to
a lower form of oxidation, the oxygen being used for the oxidation of
the organic matter or for the needs of the growing plant; while the
lower oxid of iron can more readily take up oxygen of the air and again
be converted into a higher oxid, ready again to give up a part of its
oxygen and thus serve as a carrier.
=6. Silicon= never occurs in the free state, but combined with oxygen it
forms silica, which constitutes more than one-half of the earth’s crust.
The oxid of silicon occurs in the very common form of quartz, and
likewise, as silicate of alumina, lime or magnesia. Silicon forms an
essential part of many minerals, such as the feldspars, amphiboles,
pyroxenes, and the micas, besides being an essential ingredient of many
other minerals. Silica is relatively very slightly affected by the
ordinary forces concerned in the decay of rocks, and even after the
crystals of feldspars, micas, and other common minerals occurring in
rocks have been disintegrated the silica remains as hard grains of sand,
forming the bulk of most soils. By far the larger part of silicon in
soils is in the form of grains of quartz or silica. This form, however,
is probably chemically inert in regard to plant growth, but it plays a
very important part in the physical structure of soils and in the
physical relation of soils to plant growth.
=7. Carbon= as an elementary substance occurs as diamond and graphite
and in an impure form as anthracite and bituminous coals. In peats and
mucks carbon is the chief constituent. This substance is also contained
in the organic matters of the soil known as humus, and the relation of
the carbon to nitrogen often throws important light upon the amount and
character of the nitrogenous matters. In composition with oxygen it
forms the chief food of growing plants, the carbon of the carbon dioxid
of the air being elaborated into the tissue of the plants and the oxygen
returned to the atmosphere. The content of carbon dioxid in the air is
from three to five parts per thousand by volume. As carbonates this
element helps to form some of the most important ingredients of the
earth’s crust, namely, limestones, marbles, dolomites, etc., and in an
organic form it is found in the shells of the crustaceans. The
calcareous matter of the soil, that is, the carbonates of the earths
therein found, are of the highest importance from an agricultural point
of view. The carbonates in the soil not only favor the process of
converting nitrogenous bodies into forms suitable for plant food, but
also exert a most potent influence on the physical state of the soil and
its capacity for holding water and permitting its flow to and from the
rootlets of the plant.
=8. Sulfur= occurs in nature in both the free and combined state. In the
free state it is found in volcanic regions such as Sicily, Iceland, and
the western United States. Its usual form of occurrence is in
combination with the metals to form sulfids, or with oxygen and a metal
to form sulfates. Sulfur and iron combine to form iron pyrites or iron
disulfid (FeS₂), while sulfur, oxygen, and calcium are found in gypsum,
an important fertilizing compound.
Sulfur plays an important part in the nourishment of plants, being found
in them both as sulfuric acid and in organic compounds. Methods for
estimating the sulfur in both forms will be found in another part of
this manual.
=9. Hydrogen= is a colorless, invisible gas, without taste or smell. It
occurs free in small proportions in certain volcanic gases, and in
natural gas, but its most common form is in combination with oxygen as
water (H₂O), of which it forms 11.13 per cent by weight. It also occurs
in combination with carbon to form the hydrocarbons, such as the mineral
oils (petroleum, etc.) and gases. Hydrogen is of no importance to
agriculture in a free state, but water is the most important of all
plant foods.
=10. Chlorin= occurs free in nature only in limited amounts and in
volcanic vents. Its most common form is in combination with hydrogen,
forming hydrochloric acid, or with the metals to form chlorids. It
combines with sodium to form sodium chlorid or common salt (NaCl), which
is the most abundant mineral ingredient in sea water and which can
usually be detected in rain and ordinary terrestrial waters. In this
form, also, it exists as extensive beds of rock salt, which is mined for
commercial purposes.
Chlorin is found uniformly in plants and must be regarded as an
essential constituent thereof. Common salt applied to a soil modifies
its power of attracting and holding water.
=11. Phosphorus= never occurs in nature in a free state but exists in
combination in greater or less quantities in all soils. Its combinations
are also found in large deposits of minerals known as phosphorite and
apatite and as so-called pebble deposit and phosphate rock. Phosphorus
in some sort of combination is one of the most essential elements in
animal and plant food. In animals its compounds form almost all of the
mineral matter of the bones, and in plants they are the chief
constituents of the ash of seeds.
The mineral deposits of phosphorus, as well as bones, are chiefly
tri-calcium phosphate, while the slag compound resulting from the basic
treatment of iron ores rich in phosphorus is a tetra-calcium salt.
The pebble deposits and some rock phosphates are supposed to be of
organic origin, derived from the remains of marine, terrestrial, and
aerial animals.
Cereal crops remove about twenty pounds of phosphoric acid per acre from
the soil annually and grass crops about twelve pounds. The total
phosphoric acid removed annually by the cereal and grass crops in the
United States is nearly four billion pounds.
Gautier[1] calls attention to the fact that the oldest phosphates are
met with in the igneous rocks such as basalt, trachyte, etc., and even
in granite and gneiss. It is from these inorganic sources, therefore,
that all phosphatic plant food must have been drawn. In the second order
in age Gautier places the phosphates of hydro-mineral origin. This class
not only embraces the crystalline apatites but also those phosphates of
later formation formed from hot mineral waters in the jurassic,
cretaceous, and tertiary deposits. These deposits are not directly
suited to nourish plants.
The third group of phosphates in order of age and assimilability
embraces the true phosphorites containing generally some organic matter.
They are all of organic origin. In caves where animal remains are
deposited there is an accumulation of nitrates and phosphates.
Not only do the bones of animals furnish phosphates but they are also
formed in considerable quantities by the decomposition of substituted
glycerids such as lecithin. The ammonia produced by the nitrification of
the albuminoid bodies combines with the free phosphoric acid thus
produced, forming ammonium or diammonium phosphates. The presence of
ammonium phosphates in guanos was first noticed by Chevreul more than
half a century ago.
If such deposits overlay a pervious stratum of calcium carbonate, such
as chalk, and are subject to leaching a double decomposition takes place
as the lye percolates through the chalk. Acid calcium phosphate and
ammonium carbonate are produced. By further nitrification the latter
becomes finally converted into calcium nitrate. In like manner aluminum
phosphates are formed by the action of decomposing organic matter on
clay.
Davidson,[2] explains the origin of the Florida phosphates by suggesting
that they arose chiefly through the influx of animals driven southward
during the glacial period. According to his supposition the waters of
the ocean, during the cenozoic period contained more phosphorus than at
the present time. The waters of the ocean over Florida were shallow and
the shell fish existing therein may have secreted phosphate as well as
carbonate of lime. This supposition is supported by an analysis of a
shell of _lingula ovalis_, quoted by Dana, in which there were 85.79 per
cent of lime phosphate. In these waters were also many fishes of all
kinds and their débris served to increase the amount of phosphatic
material. As the land emerged from the sea came the great glacial epoch
driving all terrestrial animals southward. There was, therefore, a great
mammal horde in the swamps and estuaries of Florida. The bones of these
animals contributed largely to the phosphatic deposits. In addition to
this, the shallow sea contained innumerable sharks, manatees, whales,
and other inhabitants of tropical waters, and the remains of these
animals added to the phosphatic store.
While these changes were taking place in the quaternary period, the
Florida Peninsula was gradually rising, and as soon as it reached a
considerable height the process of denudation by the action of water
commenced. Then there was a subsidence and the peninsula again passed
under the sea and was covered with successive layers of sand. The
limestones during this process had been leached by rain water containing
an excess of carbon dioxid. In this way the limestones were gradually
dissolved while the insoluble phosphate of lime was left in suspension.
During this time the bones of the animals before mentioned by their
decomposition added to the phosphate of lime present in the underlying
strata, while some were transformed into fossils of phosphate of lime
just as they are found to-day in vast quantities.
Wyatt,[3] explains the phosphate deposits somewhat differently.
According to him, during the miocene submergence there was deposited
upon the upper eocene limestones, more especially in the cracks and
fissures resulting from their drying up, a soft, finely disintegrated
calcareous sediment or mud. The estuaries formed during this period were
swarming with animal and vegetable life, and from this organic life the
phosphates were formed by decomposition and metamorphism due to the
gases and acids with which the waters were charged.
After the disappearance of the miocene sea there were great disturbances
of the strata. Then followed the pliocene and tertiary periods and
quaternary seas with their deposits and drifts of shells, sands, clays,
marls, bowlders, and other transported materials supervening in an era
when there were great fluctuations of cold and heat.
By reason of these disturbances the masses of the phosphate deposits
which had not been infiltrated in the limestones became broken up and
mingled with the other débris and were thus deposited in various mounds
or depressions. The general result of the forces which have been briefly
outlined, was the formation of bowlders, phosphatic débris, etc. Wyatt
therefore classifies the deposits as follows:
1. Original pockets or cavities in the limestone filled with hard and
soft rock phosphates and débris.
2. Mounds or beaches, rolled up on the elevated points, and chiefly
consisting of huge bowlders of phosphate rock.
3. Drift or disintegrated rock, covering immense areas, chiefly in Polk
and Hillsboro counties, and underlying Peace River and its tributaries.
Darton,[4] ascribes the phosphate beds of Florida to the transformation
of guano. According to this author two processes of decomposition have
taken place. One of these is the more or less complete replacement of
the carbonate by the phosphate of lime. The other is a general
stalactitic coating of phosphatic material. Darton further calls
attention to the relation of the distribution of the phosphate deposits
as affecting the theory of their origin, but does not find any peculiar
significance in the restriction of these deposits to the western ridge
of the Florida peninsula.
As this region evidently constituted a long narrow peninsula during
early miocene time it is a reasonably tentative hypothesis that during
this period guanos were deposited from which was derived the material
for the phosphatization of the limestone either at the same time or soon
after.
Darton closes his paper by saying that the phosphate deposits in Florida
will require careful, detailed geologic exploration before their
relations and history will be fully understood.
According to Dr. N. A. Pratt the rock or bowlder phosphate had its
immediate origin in animal life and to his view the phosphate bowlder is
a true fossil. He supposes the existence of some species in former times
in which the shell excreted was chiefly phosphate of lime. The fossil
bowlder, therefore, becomes the remains of a huge foraminifer which had
identical composition in its skeleton with true bone deposits or of
organic matter.
Perhaps the most complete exposition of the theory of the recovery of
waste phosphates, with especial reference to their deposit in Florida,
has been given by Eldridge.[5] He calls attention to the universal
presence of phosphates in sea water and to the probability that in
earlier times, as during the miocene and eocene geologic periods, the
waters of the ocean contained a great deal more phosphate in solution
than at the present time. He cites the observations of Bischof, which
show the solubility of different phosphates in waters saturated with
carbon dioxid. According to these observations apatite is the most
insoluble form of lime phosphate, while artificial basic phosphate is
the most soluble. Among the very soluble phosphates, however, are the
bones of animals, both fresh and old. Burnt bones, however, are more
soluble than bones still containing organic matter. Not only are the
organic phosphates extremely soluble in water saturated with carbon
dioxid, but also in water which contains common salt or chlorid of
ammonium. The presence of large quantities of common salt in sea water
would, therefore, tend to increase its power of absorbing lime
phosphates of organic origin. It is not at all incredible, therefore, to
suppose that at some remote period the waters of the ocean, as indicated
by these theories, were much more highly charged with phosphates in
solution than at the present time.
According to Eldridge, the formation of the hard-rock and soft
phosphates may be ascribed to three periods: First, that in which the
primary rock was formed; second, that of secondary deposition in the
cavities of the primary rock; third, that in which the deposits thus
formed were broken up and the resulting fragments and comminuted
material were redeposited as they now occur.
“The first of these stages began probably not later than the close of
the older miocene, and within the eocene area it may have begun much
earlier. Whether the primary phosphate resulted from a superficial and
heavy deposit of soluble guanos, covering the limestones, or from the
concentration of phosphate of lime already widely and uniformly
distributed throughout the mass of the original rock, or from both, is a
difficult question. In any event, the evidence indicates the effect of
the percolation of surface waters, highly charged with carbonic and
earth acids, and thus enabled to carry down into the mass of the
limestone dissolved phosphate of lime, to be redeposited under
conditions favorable to its separation. Such conditions might have been
brought about by the simple interchange of bases between the phosphate
and carbonate of lime thus brought together, or by the lowering of the
solvent power of the waters through loss of carbonic acid. The latter
would happen whenever the acid was required for the solution of
additional carbonate of lime, or when, through aeration, it should
escape from the water. The zone of phosphate deposition was evidently
one of double concentration, resulting from the removal of the soluble
carbonate thus raising the percentage of the less soluble phosphate, and
from the acquirement of additional phosphate of lime from the overlying
portions of the deposits.”
“The thickness of the zone of phosphatization in the eocene area is
unknown, but it is doubtful if it was over twenty feet. In the miocene
area the depth has been proved from the phosphates _in situ_ to have
been between six and twelve feet.”
The deposits of secondary origin, according to Eldridge, are due chiefly
to sedimentation, although some of them may have been due to
precipitation from water. This secondary deposition was kept up for a
long period, until stopped by some climatic or geologic change. The
deposits of phosphates thus formed in the Florida peninsula are
remarkably free from iron and aluminum, in comparison with many of the
phosphates of the West Indies.
The third period in the genesis of the hard rock deposits embraces the
time of formation of the original deposits and their transportation and
storage as they are found at the present time. The geologic time at
which this occurred is somewhat uncertain but it was probably during the
last submergence of the peninsula.
In all cases the peculiar formation of the Florida limestone must be
considered. This limestone is extremely porous and therefore easily
penetrated by the waters of percolation. A good illustration of this is
seen on the southwestern and southern edges of Lake Okeechobee. In
following down the drainage canal which has been cut into the southwest
shore of the lake the edge of the basin, which is composed of this
porous material may be seen. The appearance of the limestone would
indicate that large portions of it have already given way to the process
of solution. The remaining portions are extremely friable, easily
crushed, and much of it can be removed by the ordinary dredging
machines. Such a limestone as this is peculiarly suited to the
accumulation of phosphatic materials, due to the percolation of the
water containing them. The solution of the limestone and consequent
deposit of the phosphate of lime is easily understood when the character
of this limestone is considered.
Shaler, as quoted by Eldridge in the work already referred to, refers to
this characteristic of the limestone and says that the best conditions
for the accumulation of valuable deposits of lime phosphate in residual
débris appear to occur where the phosphatic lime marls are of a rather
soft character; the separate beds having no such solidity as will resist
the percolation of water through innumerable incipient joints such as
commonly pervade stratified materials, even when they are of a very soft
nature.
Eldridge is also of the opinion that the remains of birds are not
sufficient to account for the whole of the phosphatic deposits in
Florida. He ascribes them to the joint action of the remains of birds,
of land and marine animals and to the deposition of the phosphatic
materials in the waters in the successive subsidences of the surface
below the water line.
=12. Nitrogen= as a mineral constituent of soils, is found chiefly in
the form of nitrates, but, owing to their solubility, they can not
accumulate in soils exposed to heavy rain-falls. The gaseous nitrogen in
the soil is also of some importance, since it is in this material that
the anaerobic organisms which accumulate on the rootlets of some plants
probably act in the process of the fixation of atmospheric nitrogen in a
form accessible to plants. Nitrogen in the free state, it is believed,
is not directly absorbed into the tissues of plants. It is necessary
that it be oxidized in some way to nitric acid before it can be
assimilated. The importance of nitrogen as a plant food can not be too
highly estimated. It is as necessary to plant growth and development as
water, phosphoric acid, lime, and potash, and far more costly. While a
large quantity of nitrogen exists in the air in an uncombined state, it
is, nevertheless, one of the least abundant of the elements of high
importance in plant nutrition.
The conservation and increase of the stores of available nitrogen in the
soil is one of the chief problems occupying the attention of
agricultural chemistry. Nitrogen, which is not immediately available for
the growth of plants, is conserved and restored by natural processes in
various ways.
The waste nitrogen finds its way sooner or later to the sea, and is
restored therefrom in many forms. Sea-weeds of all kinds are rich in
recovered nitrogen. Many years ago Forchhammer[6] pointed out the
agricultural value of certain fucoids. Many other chemists have
contributed important data in regard to the composition of these bodies.
Jenkins[7] has shown from the analyses of several varieties of sea-weeds
that in the green state they are quite equal in fertilizing value to
stall manure, and are sold at the rate of five cents per bushel. These
data are fully corroborated by Goessmann.[8]
Wheeler and Hartwell[9] give the fullest and most systematic discussion
which has been published of the agricultural value of sea-weeds.
Sea-weed was used as a fertilizer as early as the fourth century, and
its importance for this purpose has been recognized more and more in
modern days, especially since chemical investigations have shown the
great value of the food materials contained therein.
To show the commercial importance of sea-weed, it is only necessary to
call attention to the fact that in 1885 its value as a fertilizer in the
State of Rhode Island was $65,044, while the value of all other
commercial fertilizers was $164,133. While sea-weed, in a sense, can
only be successfully applied to littoral agriculture, yet the extent of
agricultural lands bordering on the sea is so great as to render its
commercial importance of the highest degree of interest.
A large amount of nitrogen is also recovered from the sea in fishes. It
is shown by Atwater[10] that the edible part of fishes has an unusually
high percentage of protein. In round numbers, about seventy-five per
cent of the water free edible parts of fish are composed of albuminoids.
Some kinds of fish are taken chiefly for their oil and fertilizing
value, as the menhaden. Squanto,[11] an American Indian, first taught
the early New England settlers the manurial value of fish.
Immense quantities of waste nitrogen are further secured, both from sea
and land, by the various genera of birds. The well-known habit of birds
in congregating in rookeries during the night and at certain seasons of
the year tends to bring into a common receptacle the nitrogenous matters
which they have gathered and which are deposited in their excrement and
in the decay of their bodies. The feathers of birds are particularly
rich in nitrogen, and the nitrogenous content of the flesh of fowls is
also high. The decay of remains of birds, especially if it take place
largely excluded from the leaching of water, tends to accumulate vast
deposits of nitrogenous matter. If the conditions in such deposits be
favorable to the processes of nitrification, the whole of the nitrogen,
or at least the larger part of it, which has been collected in this
débris, becomes finally converted into nitric acid and is found combined
with appropriate bases as deposits of nitrates. The nitrates of the
guano deposits and of the deposits in caves arise in this way. If these
deposits be subject to moderate leaching the nitrate may become
infiltered into the surrounding soil, making it very rich in this form
of nitrogen. The bottoms and surrounding soils of caves are often found
highly impregnated with nitrates.
While for our purpose, deposits of nitrates only are to be considered
which are of sufficient value to bear transportation, yet much interest
attaches to the formation of nitrates in the soil even when they are not
of commercial importance.
In many of the soils of tropical regions not subject to heavy
rain-falls, the accumulation of these nitrates is very great. Müntz and
Marcano[12] have investigated many of these soils to which attention was
called first by Humboldt and Boussingault. They state that these soils
are incomparably more rich in nitrates than the most fertile soils of
Europe. The samples which they examined were collected from different
parts of Venezuela and from the valleys of the Orinoco as well as on the
shore of the Sea of Antilles. The nitrated soils are very abundant in
this region of South America where they cover large surfaces. Their
composition is variable, but in all of them carbonate and phosphate of
lime are met with and organic nitrogenous material. The nitric acid is
found always combined with lime. In some of the soils as high as thirty
per cent of nitrate of lime have been found. Nitrification of organic
material takes place very rapidly the year round in this tropical
region. These nitrated soils are everywhere abundant around caves, as
described by Humboldt, caves which serve as the refuge of birds and
bats. The nitrogenous matters, which come from the decay of the remains
of these animals, form true deposits of guano which is gradually spread
around, and which, in contact with the limestone and with access of air,
suffers complete nitrification with the fixation of the nitric acid by
the lime.