591 H62.
UC-NRLF
75
OJ
r>
to
o
JUNE, 1875.
No. 14.
BULLETIN
OF THE
UNIVERSITY OF CALIFORNIA
SYNOPSIS OF A COUESE OF LECTUKES
ON THE
Origin, Composition, and Functions of Soils, and their bearing on Agriculture.
Delivered at the University of California, during the first Term, 1874-5. PROF. EUG. W. HILGAKD.
Definition of " Soil" :
Different meaning as referred to different plants. Judging of Soils by the natural growth. Different forms of trees, etc., on different soils, and er- rors resulting from their neglect.
Exceeding complication of considerations in judging of the value and nature of soils, involving a very varied knowledge and careful judgment, or long and costly experimenting.
Hence necessity for scientific examination on the spot, and mechanical and chemical analysis of soils; to serve as guides for practice, or practical tests.
Necessity for cooperation between farmers and scientists, to prevent endless mistakes and expense. Experimental Stations.
s 95
-73261
University Press, Berkeley
BULLETIN OF THE
ORIGIN OF SOILS.
Mechanical and chemical disintegration of rocks.
Mineral composition of important crystaline rocks.
Chief rock-forming minerals.
Quartz, the Feldspars, Mica, Hornblende, Augite, Talc
(Serpentine.)
Calcareous Spar or Calcite, Dolomite, Gypsum, Apatite. Decomposition of these by atmospheric agencies; Water,
Carbonic Acid, Oxygen, Ammonia. Quartz — soluble and insoluble forms. Feldspars — formation of clays and carbonates. Hornblende and Augite — formation of ferruginous clays,
loams, carbonates. Mica — difficult to decompose.
Sedimentary rocks — Sandstones, shales, limestones, how formed; their composition.
Character of soils derived from these several rocks.
Feldspar the source of potash.
Apatite that of phosphates. Decomposition greatly accelerated by pulverization,
Effects of frost on rocks,
Mechanical Attrition.
Mechanical processes active in soil formation. Action of flowing water.
Action of water charged with sand and gravel. Action of glacier ice.
COMPOSITION OF SOILS.
General Soil Ingredients are
Unaltered Eock-powder.
Altered Eock-powder.
Clay.
Vegetable matter. According to the proportion of these they may be classed as
LIGHT SOILS HEAVY SOILS
Sandy, Humous. Clayey, Siliceous.
Definition of these terms.
Great diversity of sub-classification, adapted to local circum- stances, and locally very important. 96
V
UNIVERSITY OF CALIFORNIA.
DETERMINATION OF CHARACTEK OF SOILS.
Observation in the Field — Derivation, Position, Depth, Substratum, Natural growth, Climate.
Experience in cultivation.
Taking of fair specimens — difficulty — precautions.
Examination of subsoils best adapted to general pur- poses.
PHYSICAL PROPERTIES of soils — quite as important as chemical composition.
"Lightness" — "Heaviness" — Porosity — Absorption of aqueous Vapor — Water-holding power — Capillary co- efficient— Color — Specific" gravity.
Difficulty and tediousness of direct determination of these. Mechanical analysis as a substitute, sufficient for practical pur- poses.
Elutriation. Subsidence method — faults.
Hydraulic method.
Apparatus of Noebel — Fresenius — Mueller — Schoene.
Mixed character of sediments, and inconstancy of re- sults. Causes — "Flocculation." Preliminary preparation — Boiling — removal of gravel and clay
prior to washing.
The Churn Elutriator or Soil-washer — Construction — Precau- tions in use.
Character and nomenclature of sediments.
Direct determination of Clay by precipitation.
Action of common Salt. Lime.
Influence in formation of bars at river mouths. Importance of Flocculation — Effects of tillage — "Woolly" condi- tion— Tamping of clays.
Molecular properties of sediments — absorptive coeffi- cients— mechanical resistance.
Estimation of tillability of soils; influence of sediments on " lightness " and " heaviness ;" clay not the only factor of "heaviness."
Influence of Flocculation.
Porosity ^s. Resistance to tillage. Absorbing power of Soils.
Not in direct ratio to clay. Examples.
Influence of Sediments — of Ferric Oxide — of Humus. 97
BULLETIN OF THE
"Humus." Its origin, and influence on the physical proper- ties of Soils. Summary of functions of physical soil ingredients,
CHEMICAL COMPOSITION, AND ANALYSIS OF SOILS.
Elements concerned in formation of Soils.
"Whence derived.
Nutritive and inert Soil ingredients.
Ash ingredients of Plants; derived from Soil; Carbon from Air, Nitrogen from both.
A priori view of Soil analysis — Composition of crops.
Fallacies. Distinction between available and unavailable portion of nutritive soil ingredients.
Difficulties, and attempts to overcome them.
Causes of failure — rejection of soil analysis.
Professor Johnson's arguments.
Discussion of objections. What soil analysis may fairly claim to do for practice, in application to virgin soils.
To identify and distinguish soils, thus making past ex- perience available in new regions.
To determine their prominent characteristics, both phys- ical and chemical.
To show abundance, scarcity or absence of important soil ingredients, thus indicating the general adapta- tion, permanent value, and cheapest mode of im- provement, or maintenance of fertility.
Always provided, that systematic observation on the spot, of all circumstances influencing cultivation, and comparative examination' of soils of similar origin, be kept in view. Mere columns of figures of little use. Taking of Specimens — details.
Methods of chemical analysis; elements to be determined.
Choice of solvents. General Analysis — Details.
Determination of Phosphoric Acid.
Determination of "Humus" and Nitrogen.
FUNCTIONS OF THE SEVEEAL CHEMICAL SOIL INGREDIENTS, AND THEIR
CONDITION IN THE SOIL. Outlines of Vegetable Physiology.
Experiments on growth of plants in soils devoid of or- ganic matter; in solutions.
Object of the course mainly the consideration of the 98
UNIVERSITY OF CALIFORNIA.
indispensable soil ingredients, their distribution, func- tions and sources of supply. Distribution of Ash ingredients in Horse Chestnut, Beet, Cereals,
etc.
Amount and character of ashes in old and young leaves, stems, wood, etc.
Metallic Elements.
*
Potash. Percentage contained in soils. Examples. How contained. Feldspar — Zeolitic compounds. Mechan- ical absorption. Liebig's experiments. Laws of surface absorption. Composition of drain waters. Root crops especially exhaustive of Potash. Potash manures in general. Soda. Inferior in importance to Potash.
, Small amount in soils — easily washed out, yet rarely needs
to be supplied. Salty soils — Salt plants. Sodium salts used in agriculture. Oflwr Alkalies in minimum quantities.
Lime. Amount usually present in soils. Relation to Po- tash. Nutritive as well as stimulant. Largely present in stems. General importance as a soil ingredient, both physical
and chemical.
Effects on mechanical condition of Soil. "Flocculation."
Renders soils loose, pervious, tillable — "warms" them. Chemical Effects of Lime — "fallowing" action.
Effects on organic decay, and formation of "humus." How present — carbonate, sulphate, phosphate, humate. Natural characteristics of calcareous soils — their growth,
color, thriftiness. Examples. Importance of a supply of lime to Agriculture. Magnesia. Like lime, important stem ingredient.
Rarely deficient in soils — seldom needs to be supplied.
Partially replaces lime. Percentage in Soils. Numerical relation to potash. How
present in soils. Copiously carried off in drain waters. Soluble magnesium
salts injurious to vegetation.
Alumina. Not a true ash ingredient, though often found in ashes. 99
6 BULLETIN OF THE
Origin of clays. Varieties. Kaolin. Pipe-Clay. "Soap- stone. " Brick Loam.
Tints imparted to clays by Iron — changes by oxidation and reduction.
By Manganese — by Carbon — how recognized.
Recapitulation of the properties of clay as a soil ingredient. Iron. Widely diffused, omnipresent, Nutritive as well as me- chanically important. Tonic.
Hygroscopic efficacy of ferric oxide; chemical inertness.
Proto salts poisonous. Reduction of ferric oxide by veg- etable matters. Yellow mud and blue mud.
Bottom lands — blue subsoils — "rusting" soils.
Iron in surface soils and subsoils.
"White or "Crawfishy" soils — Black pebble or bog ore sub- soils. Deterioration of soil thereby: causes.
Chalybeate Springs. Formation of Ferruginous sand- stone.
Manganese. Vicarious of Iron. Less important. Copper. In very minute quantities, in wheat, potashes, etc.
Non-metallios.
Silicon. Silica predominant ingredient of soils. Sand and silicates.
Apparently unessential to plants but very largely ab- sorbed by grasses, pines, etc. "Lodging" of grain. Silica in drain waters — Acid soils — Action of lime. Sulphur. Sulphates omnipresent. Small percentage in soils. Often deficient.
Cheaply supplied by gypsum. Sulphates in drain water. Effects of fermentation on sulphates. Iron pyrites, etc.
Remedies. Phosphorus. Phosphates of highest importance to nutrition of
plants and animals.
Derivation of soil phosphates. Small percentage — re- lation to Potash. Accumulation in seeds. Small-seeded plants on soils
poor in phosphates.
Their deficiency a common cause of sterility. Must be currently restored to cultivated soils. Effect of bone-dust on old pastures. Chlorine. Present in all soils and plant ashes.
100
UNIVERSITY OF CALIFORNIA.
Correlative with Sodium. Karely deficient. Fluorine. Very generally present in small quantities.
Most largely in bones. Iodine. Common, in traces.
Carbon. Ultimately derived from air: directly in part from soil. Formation of humus by decay of vegetable matter. (Physical effects of humus on soils — see above). Chemical effects on soil ingredients.
Action of Crenic and Apocrenic acids.
Oxidation of humus. Production of carbonic acid, the
universal solvent.
Direct absorption of soluble vegetable matter. Hydrogen. Absorbed by plants in shape of water. Nitrogen. Highly important nutritive and constituent ingredi- ent. Flesh-former. Free nitrogen of air not assimilable. Ammonia and nitric acid of atmosphere — absorbed by
soil. Inadequate for crops. Nitrogen in soil. How contained? Small percentage
and largely unavailable. Connection with humus — Nitrification accompanying
oxidations, evaporation etc.
Ozonization. Formation of Hydrogen Peroxide. Possible agency of microscopic plants in soil. Necessity for artificial supply of Nitrogen for crops. Ni- trogen Theory versus "Mineral" Theory. General effects of nitrogenous manures on plants.
EXHAUSTION OF SOILS. Eecapitulation :
' 'All plant ingredients must be simultaneously present in sufficient quantities. Absence of one renders all inert. " "Supplying that one deficient ingredient enormously pro- fitable."
"Excess of any lies inert in the soil as dead capital." Hence the necessity for
Eolation of Crops. Causes of necessity for rotation. Abstraction of different
ingredients in unequal degrees by different crops. Different depth of roots — fibrous and tap roots. Examples.
Eotation utilizes soil resources best. Makes interest ac- 101
BULLETIN OF THE
crue on the whole soil capital. Should be the guidinj principle in all cases. Order of rotation can be determined by analysis of crops
MODIFICATION OF SOILS BY ARTIFICIAL MEANS. By mechanical operations.
Tillage secures looseness, easy penetration of roots, cii
culation of air, soil-gases and water. How nature tills — mulching, frost, wetting and dryii Artificial condition of culture; overriding of natural ac
aptations of soils and localities. Hence necessity fo]
tillage, preparation and cultivation. Importance of depth of soil for equalization of extreme]
and safety of crops. Depth of soil equivalent to cultivating larger areas, bu|
with less labor and greater safety of crops. In shallow soils, crops are at the mercy of seasons. Heavy soils need thorough tillage most.
Deep tillage — sub-soiling. Chemical and physical differences between soil and sub]
soil. Stirring versus turning up — conditions under which eithej
may be useful or injurious. Treatment of subsoiled lands, for maintenance of profit]
able productiveness. Subsoiling not a preventive of exhaustion.
Drainage — Under draining. "Believes wet soils:" but does a great deal more — us(
ful in all soils. General plan of underdrains. Various methods, tilt
drains, log-drains, brush-drains, etc. Mode of action, difficulties and remedies. Action of underdrains on clay soils. Analogy to subsoil^
ing; protection against drouth by deepening of soil. Drained lands can be tilled at all times; are less cold; less
liable to surface washing. Advantages to public health. By addition of Material — (a.) "Mechanical Manures."
Not often profitable by themselves — should be combined
with other objects. Management of natural drainage to effect desirable
changes.
192
Gaylamount •-.** Pamphlet
Binder Gaylord Bros., Inc.
Stockton, Calif. T.M.Reg. U.S. Pat. Off.
THE UNIVERSITY OF CALIFORNIA LIBRARY