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

by Eugene W. Hilgard

CHAPTER IX.

Soil and Subsoil (continued), [142].—Organisms Influencing Soil-Conditions. Bacteria, [142].—Micro-organisms of the Soil. Bacteria, Moulds, Ferments, [142].—Numbers at Various Depths, given by Early Observers, [142].—Investigations of Hohl; Mayo and Kinsley. Tables, [143].—Multiplication of the Bacteria, [144].—Aerobic and Anaerobic Bacteria, [144].—Food Materials required, [145].—Functions of the Bacteria, [145].—Nitrifying Bacteria. Figures, [146].—Conditions of their Activity. Table, [146].—Effects of Aeration and Reduction, [147].—Unhumified Organic Matter does not Nitrify, [148].—Unhumified Vegetable Matter, Functions in Soils, [148].—Denitrifying Bacteria. Figures, [148].—Ammonia-forming Bacteria. Figures, [149].—Alinit, [149].—Effects of Bacterial Life on Physical Soil Conditions, [149].—Root-bacteria, or Rhizobia of Legumes, [150].—Figures of Root Excrescences and Corresponding Bacteroids, [152].—Varieties of Forms, [154].—Mode of Infection, [154].—Cultural Results, [155].—Table Showing Increased Production by Soil Inoculation, [155].—Other Nitrogen-absorbing Bacteria, [156].—Distribution of Humus in the Surface Soil, [157].—Fungi, Moulds and Algae, [157].—Animal Agencies—Earthworms, Insects, Burrowing Quadrupeds, [158].

CHAPTER X.

Soil and Subsoil in their Relations to Vegetation, [161].—Physical Effects of the Percolation of Surface Waters, [161].—Chemical Effects; Calcareous Subsoils and Hardpans, [161].—“Rawness” of Subsoils in Humid Climates, [162].—Subsoils in the Arid Region, [163].—Deep Plowing and Subsoiling in the Arid Region; examples of Plant growth on Subsoils, [164].—Resistance to Drought, [167].—Root System in the Humid Region, [168].—Figures of the Root System of an Eastern (Wisconsin) Fruit Tree, [168].—Comparison of Root Development in the Arid and Humid Regions, [169].—Prune on Peach Root, [169].—Adaptation of Humid Species to Arid Conditions, [169].—Grapes, [170].—Kentucky and California Maize, [175], [176].—Hops, [172].—Deep-Rooting in the Arid Region, [174].—Goose Foot and Figwort, [174].—Importance of Proper Substrata in the Arid Region, [173].—Injury from Impervious Substrata. Figure, [177].—Faulty Lands of California. Figure, [178].—Shattering of Dense Substrata by Dynamite, [181].—Leachy Substrata, [182].—“Going-back” of Orchards, [182].—Hardpan, Formation and Varieties, [183].—Nature of the Hardpan Cements, [184].—Bog Ore, Moorbedpan and Ortstein; Calcareous and Alkali Hardpan, [184].—The Causes of Hardpan, [185].—“Plowsole,” [186].—Marly Substrata, [186].

CHAPTER XI.

The Water of Soils. Hygroscopic and Capillary Moisture, [188].—General Properties, [188].—Physical Factors of Water compared with other Substances. Table, [188].—Capillarity or Surface Tension, [189].—Heat Relations, [190].—Density, [190].—Specific Heat and its Effects, [190]. Ice, [191].—Vaporization, [191].—Solvent Power, [191].—Water-requirements of Growing Plants, [192].—Evaporation from Plants in Different Climates, [192].—Relations between Evaporation and Plant Growth. Table, [193].—Fortier’s Experiments. Figure, [194].—Different Conditions of Soil Water, [196].—Hygroscopic Water in Soils; Table, [196].—Influence of Temperature and Air-Saturation, [197].—Utility of Hygroscopic Water to Plant Growth, [199].—Mayer’s Experiments, [200].—Summary, [200].—Capillary Water, [201].—Ascent of Water in Soil-Columns. Table, [202].—Ascent in Uniform Sediments. Figure, [204].—Maximum and Minimum Water-holding Power, [207].—Capillary Water held at different Heights in a Soil Column. Table, [208].—Capillary Action in Moist Soils, [210].—Proportion of Soil Moisture Available to Plants, [211].—Moisture Requirements of Crops in the Arid Region, [211].—Tables of Observations in California, [214].

CHAPTER XII.

Surface, Hydrostatic and Ground Water. Percolation, [215].—Amount of Rainfall, [215].—Natural Disposition of Rain Water, [216].—The Surface Runoff, [216].—Washing-away and Gullying in the Cotton States, [217].—Injury in the Arid Regions, [219].—Deforestation, [219].—Prevention of Injury to Cultivated Lands from Excessive Runoff, [220].— Absorption and Movements of Water in Soils, [221].—Determination of Rate of Percolation. Diagram, [221].—Summary, [224].—Influence of Variety of Grain-sizes, [224].—Table of King’s Experiments, [224].—Percolation in Natural Soils. Figure, [225].—Ground or Bottom Water, [227].—Lysimeters, Surface of Ground Water; Variations, [227].—Depth of Ground Water most Favorable to Crops, [228].—Moisture Supplied by Tap Roots, [229].—Reserve of Capillary Water, [229].—Injurious Rise of Bottom Water from Irrigation, [230].—Consequences of the Swamping of Irrigated Lands; Prevention, [231].—Permanent Injury to certain Lands, [231].—Reduction of Sulfates, [232].—Ferruginous or Red Lands, [233].

CHAPTER XIII.

Water of Soils; The Regulation and Conservation of Soil, Moisture; Irrigation, [234].—Loosening of the Surface, [234].—Effects of Underdrains; Rain on Clay Soils, [235].—Winter Irrigation, [236].—Methods of Irrigation, [236].—Surface Sprinkling, [237].—Flooding, [237].—Check Flooding. Furrow Irrigation, [237], [238].—Figure Showing Penetration, [239].—Figure Showing Faulty Irrigation in Sandy Lands, [239].—Distance between Furrows and Ditches, [241].—Irrigation by Lateral Seepage, [242].—Basin Irrigation of Trees and Vines; Advantages and Objections, [243].—Irrigation from Underground Pipes, [245].—Quality of Irrigation Waters, [246].—Saline Waters; Figures of Effects on Orange Trees, [246].—Limits of Salinity, [246].—Mode of Using Saline Irrigation Waters; Apparent Paradox, [249].—Use of Drainage Waters for Irrigation, [250].—“Black Alkali” Waters, [250].—Variations in the Salinity of Deep and Shallow Wells, [250].—Muddy Waters, [251].—The Duty of Irrigation Waters, [251].—Causes of Losses, [252].—Loss by Percolation. Figure, [252].—Evaporation, [253].—Tables Showing same at California Stations, [255].—Evaporation in Different Climates; Table, [255].—Evaporation from Reservoirs and Ditches, [257].—Prevention of Evaporation; Protective Surface Layer, [257].—Illustrations of Effects of Tillage; Table, [258].—Evaporation through Roots and Leaves, [262].—Weeds waste Moisture, [264].—Distribution of Moisture in Soils as Affected by Vegetation, [264].—Forests and Steppes, [265].—Eucalyptus for Drying Wet Lands, [265].—Mulching; Effects on Temperature and Moisture, [266].