Soils, their formation, properties, composition, and relations to climate and plant growth in the humid and arid regions

by Eugene W. Hilgard

CHAPTER XIX.

Analysis of Virgin Soils by Extraction with Strong Acids and its Interpretation, [340].—Loughridge’s Investigation on Strength of Acid and Time of Digestion, [340].—Writer’s Method, [342].—Virgin Soils with High Plant-food Percentages are always Productive. Table, [343].—Discussion of Table, [343].—Low Plant-food Percentages not always Indication of Sterility, [346].—What are “Adequate” Percentages of Potash, Lime, Phosphoric Acid and Nitrogen, [347].—Soil-Dilution Experiments, [347].—Table of Compositions, [350].—Figures of Plants and their Root-Development, [351].—Limitation of Root Action, [351].—Lowest Limits of Plant-food Percentages and Productiveness Found in Virgin Soils, [353].— Limits of Adequacy of the Several Plant-food Percentages in Virgin Soils, [353].—Lime a Dominant Factor in Interpretation, [353].—Potash, [354].—Phosphoric Acid, [355].—Action of Lime and Ferric Oxid, [355].—Table of Hawaiian Ferruginous Soils, [356].—Unavailability of Ferric Phosphate, [356].—Nitrogen, [357].—Nitrification of the Organic Matter of the Soil, [358].—Analysis of Soil from the Ten-Acre Tract at Chino, Cal., [358].—Experiments and Results; Matière Noire the Only Guide, [360].—What are Adequate Nitrogen Percentages in the Humus? [360].—Table of Humus and Nitrogen-Content of Californian and Hawaiian Soils, [361].—Confirmatory Experiment. Figure, [362].—Data for Nitrogen-Adequacy. Table, [363].—Influence of Lime upon Soil Fertility, [365].—“A Lime Country is a Rich Country,” [365].—Effects of High Lime-Content in Soils, [365].—Table of Soils showing Low Phosphoric Acid with High and Low Lime-Content, [366].—What are Adequate Lime-percentages? Differ for Light and Heavy Soils, [367].—Table Showing Need of High Lime Percentages in Heavy Clay Soils, [368].—European Standards for Land Estimates, [369].—Maercker’s Table, [369].

CHAPTER XX.

Soils of the Arid and Humid Regions, [371].—Composition of Good Medium Soils; Table, [371].—Criteria of Lands of the Two Regions, [371].—Tables of Soil-Composition in Both Regions, [372].—Soils of the Humid Region governed by Time, [374].—Soils of the Arid Region Governed by Moisture, [374].—Lime and Magnesia Uniformly High in Arid Soils, Despite Scarcity of Limestone Formations; Potash also High, [374].—General Comparison of the Soils of the Arid and Temperate Humid Regions, [375].—Basis of Same, [376].—New Mexico and Analysis of Soil, [376].—General Table, [377].—Discussion of the Table, [378].—Lime; Summary of Physical and Chemical Effects of Lime Carbonate in Soils, [378].— Discussion of Summary, [379].—Magnesia: Its role in Plant Nutrition, [381].—Manganese: Its Stimulant Action, [383].—The “Insoluble Residue” or Silicates, [384].—Soluble Silica and Alumina, [384].—Analysis of Clay from Soil, [385].—Difference in Sand of Arid and Humid Regions. Table, [386].—Soluble Silica or Hydrous Silicates more Abundant in Arid than in Humid Soils, [388].—Aluminic Hydrate. Table, [389].—Retention of Soluble Silica in Alkali Soils, [391].—Ferric Hydrate, [392].—Phosphoric Acid, [392].—Sulfuric Acid, [394].—Potash and Soda, Retained more in Arid Soils, [394].—Arid Soils Rich in Potash, [395].—Humus, Low in Arid Soils, but Rich in Nitrogen, [396].—The Transition Region, [397].

CHAPTER XXI.

Soils of Arid and Humid Regions Continued, [398].—Soils of the Tropics, [398].—Humus in Tropical Soils, [399].—Investigations of Tropical Soils, [401].—Soils of Samoa and Kamerun, [402].—Soils of the Samoan Islands, [403].—Soils of Kamerun, [404].—Soils of Madagascar, [405].—Soils of India, [410].—The Indo-Gangetic Plain, [411].—The Brahmaputra Alluvium in Assam, [413].—Black Soils of Deccan, [414].—Red Soils of the Madras Region, [415].—Laterite Soils, [416].—Influence of Aridity upon Civilization, [417].—Preference of Ancient Civilizations for Arid Countries, [417].—Irrigation Necessitates Co-operation, [419].—High and Permanent Productiveness of Arid Soils Induces Permanence of Civil Organization, [419].

CHAPTER XXII.

Alkali Soils, their Nature and Composition, [422].—Alkali Lands vs. Seashore Lands, [422].—Origin, [422].—Deficient Rainfall, [423].—Predominant Salts, [423].—Geographical Distribution, [424].—Their Utilization of World-wide Importance, [424].—Repellent Aspect, Plate, [424].—Effects of Alkali upon Culture Plants. Figures of Apricot Trees, [426].—Nature of the Injury, External and Internal, [426].—Effects of Irrigation, [428].—Leaky Irrigation Ditches, [429].—Surface and Substrata of Alkali Lands, [429].—Vertical Distribution of the Salts in Alkali Soils, [429].—How Native Plants Live, [430].—Figures of various Phases of Reclamation, [431].—Upward Translocation from Irrigation, [433].—Distribution of Alkali in Sandy Lands, [433].—In Heavier Lands, [436].—Salton Basin or Colorado Delta, [436].—Diagram of Alkali Distribution in Same, [438].—Horizontal Distribution of Alkali Salts in Arid Lands, [439].—Alkali in Hill Lands, [439].—Usar Lands of India, [440].—“Szek” Lands of Hungary, [440].—Alkali Lands of Turkestan, [441].—Composition and Quantity of Salts Present, [441].—Nutritive Salts, [441].—Black and White Alkali. Tables, [442].—Estimation of Total Alkali in Land, [444].—Composition of Alkali Soils as a whole. Tables, [445].—Presence of much Carbonate of Soda, [448].—Cross Section of an Alkali Spot. Table, [448].—Reactions between the Carbonates and Sulfates of Earths and Alkalies. Figure of Curve, [449].—Inverse Ratios of Alkali Sulfates and Carbonates. Diagrams, [451].—Exceptional Conditions, [453].—Summary of Conclusions, [453].

CHAPTER XXIII.

Utilization and Reclamation of Alkali Land, [455].—Alkali-resistant Crops, [455].—Counteracting Evaporation, [455].—Turning-under of Surface Alkali, [456].—Shading, [457].—Neutralizing Black Alkali, [457].—Removing the Salts from the Soils, [458].—Scraping off, [458].—Leaching-Down. Figure, [459].—Underdrainage, the Final and Universal Remedy for Alkali, [460].—Possible Injury to Land by Excessive Leaching, [462].—Difficulty in Draining “Black” Alkali Land, [462].—Swamping of Alkali Land, [463].—Removal of Alkali Salts by Certain Crops, [463].—Tolerance of Alkali by Culture Plants, [463].—Relative Injuriousness of the several Salts. Effects on Sugar Beets, [464].—Table of Tolerances; Comments on same, [467].—Saltbushes and Native Grasses. Australian Saltbushes, [469].—Modiola; Native and Cultivated Grasses, [469].—Other Herbaceous Crops, [472].—Legumes, [472].—Mustard Family, [473].—Sunflower Family, [473].—Root Crops, [474].—Stem Crops, [475].—Textile Plants, [475].—Shrubs and Trees, [475].—Vine, Olive, Date, Citrus Trees. Deciduous Orchard Trees. Timber and Shade Trees, [475].—Inducements toward the Reclamation of Alkali Lands, [481].—Wheat on Reclaimed Land at Tulare; Figure, [482].—Need of Constant Vigilance, [484].