Chapter I: Front Matter

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SOILS

THEIR FORMATION, PROPERTIES, COMPOSITION,
AND RELATIONS TO CLIMATE AND PLANT GROWTH
IN THE HUMID AND ARID REGIONS

BY
E. W. HILGARD, PH.D., LL.D.,

PROFESSOR OF AGRICULTURE IN THE
UNIVERSITY OF CALIFORNIA, AND DIRECTOR
OF THE CALIFORNIA AGRICULTURAL EXPERIMENT STATION

New York
THE MACMILLAN COMPANY
LONDON: MACMILLAN & CO., LTD.
1921

COPYRIGHT, 1906,
BY THE MACMILLAN COMPANY.

Set up and electrotyped. Published July, 1906.

Norwood Press:
Berwick & Smith Co., Norwood, Mass., U.S.A.

SUMMARY OF CHAPTERS.

1. ORIGIN AND FORMATION OF SOILS.
Introduction.
Chapter I. Physical Processes of Soil Formation.
“ II. Chemical Processes of Soil Formation.
“ III. Chief Soil-forming Minerals.
“ IV. The Various Rocks as Soil-Formers.
“ V. Minor Mineral Ingredients of Soils. Mineral
Fertilizers. Minerals Injurious to Agriculture.

2. PHYSICS OF SOILS.
Chapter VI. Physical Composition of Soils.
“ VII. Density, Pore Space, and Volume-Weight of Soils.
“ VIII. Soil and Subsoil; Causes and Processes of
Differentiation; Humus.
“ IX. Soil and Subsoil; Organisms Influencing
Soil-Conditions. Bacteria.
“ X. Soil and Subsoil in their Relations to Vegetation.
“ XI. Water of Soils; Hygroscopic and Capillary Moisture.
“ XII. Water of Soils; Surface, Hydrostatic, and Ground
water; Percolation.
“ XIII. Water of Soils; Conservation and Regulation of
Soil Moisture. Irrigation.
“ XIV. Absorption by Soils of Solids from Solutions.
Absorption of Gases. The Air of Soils.
“ XV. Colors of Soils.
“ XVI. Climate.
“ XVII. Relations of Soils and Plant-Growth to Heat.

3. CHEMISTRY OF SOILS.
Chapter XVIII. Physico-Chemical Investigation of Soils in
Relation to Crop Production.
“ XIX. Analysis of Virgin Soils by Extraction with
Strong Acids, and its Interpretation.
“ XX. Soils of Arid and Humid Regions.
“ XXI. Soils of Arid and Humid Regions continued.
“ XXII. Alkali Soils, their Nature and Composition.
“ XXIII. Utilization and Reclamation of Alkali Lands.

4. SOILS AND NATIVE VEGETATION.
Chapter XXIV. Recognition of the Character of Soils from their
Native Vegetation. Mississippi.
“ XXV. Recognition of the Character of Soils from their
Native Vegetation. United States at large, Europe.
“ XXVI. Vegetation of Saline and Alkali Lands.

TABLE OF CONTENTS.

PREFACE xiii

INTRODUCTION, xxiii.—Definition of Soils, xxiii.—Elements
Constituting the Earth’s Crust, xxiii.—Average Quantitative
Composition of the Earth’s Crust, xxiii.—Clarke’s Table,
xxiv.—Oxids Constitute Earth’s Crust, xxiv.—Elements
Important to Agriculture; Table, xxv.—The Volatile Part of
Plants, xxvi.

CHAPTER I.
AGENCIES OF SOIL FORMATION, 1.—1. _Physical Agencies_,
1.—Effects of Heat and Cold on Rocks, 1.—Unequal
Expansion of Crystals, 2.—Cleavage of Rocks, 3.—Effects
of Freezing Water, 3.—Glaciers; Figure, 3.—Glacier Flour
and Mud, 4.—“Green” and “White” Rivers, 4.—Moraines,
5.—Action of Flowing Water, 5.—Enormous Result of
Corrasion and Denudation, 6.—Effects of Winds, 8.—Dunes,
8.—Sand and Dust Storms in Deserts, Continental
Plateaus and Plains, 8.—Loess of China, 9.—Migration
of Gobi Lakes, 9.—_Classification of Soils_, 10.—Their
Physical Constituents, 10.—Sedentary or Residual Soils,
11.—Colluvial Soils, 12.—Alluvial Soils. Diagram,
12.—Character of these Soil Classes, 13.—Richness of
Flood-plain and Delta Lands, 14.—Lowering of the Land
Surface by Soil Formation, 15.