Elements of the Nature and Properties of Soils Brady 3e Elements of the Nature and ISBN 978-1-29203-929-9 Properties of Soils Nyle C. Brady Raymond Weil 9 781292 039299 Third Edition Pearson New International Edition Elements of the Nature and Properties of Soils Nyle C. Brady Raymond Weil Third Edition Pearson Education Limited Edinburgh Gate Harlow Essex CM20 2JE England and Associated Companies throughout the world Visit us on the World Wide Web at: www.uk © Pearson Education Limited 2014 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without either the prior written permission of the publisher or a licence permitting restricted copying in the United Kingdom issued by the Copyright Licensing Agency Ltd, Saffron House, 6–10 Kirby Street, London EC1N 8TS.
All trademarks used herein are the property of their respective owners. The use of any trademark in this text does not vest in the author or publisher any trademark ownership rights in such trademarks, nor does the use of such trademarks imply any affiliation with or endorsement of this book by such owners. ISBN 10: 1-292-03929-9 ISBN 10: 1-269-37450-8 ISBN 13: 978-1-292-03929-9 ISBN 13: 978-1-269-37450-7 British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library Printed in the United States of America P E A R S O N C U S T O M L I B R A R Y Table of Contents Glossary of Soil Science Terms Nyle C. The Soils Around Us Nyle C.
Formation of Soils from Parent Materials Nyle C. Soil Classification Nyle C. Soil Architecture and Physical Properties Nyle C. Soil Water: Characteristics and Behavior Nyle C.
Soil and the Hydrologic Cycle Nyle C. Soil Aeration and Temperature Nyle C. The Colloidal Fraction: Seat of Soil Chemical and Physical Activity Nyle C. Soil Acidity, Alkalinity, Aridity, and Salinity Nyle C.
Organisms and Ecology of the Soil Nyle C. Soil Organic Matter Nyle C. Nutrient Cycles and Soil Fertility Nyle C. Practical Nutrient Management Nyle C.
Soil Erosion and Its Control Nyle C. Soils and Chemical Pollution Nyle C. Weil 605 Appendix: World Reference Base, Canadian, and Australian Soil Classification Systems Nyle C. Weil 637 Appendix: SI Units, Conversion Factors, Periodic Table of the Elements, and Plant Names Nyle C.
Weil 643 Global Soil Regions Nyle C. Weil 649 Index 653 II Glossary of Soil Science Terms1 A horizon The surface horizon of a mineral somewhat similar in appearance, to fungal field-crop production and soil management. soil having maximum organic matter accumula- hyphae. Includes many members of the order The scientific management of land.
tion, maximum biological activity, and/or eluvi- Actinomycetales. air porosity The proportion of the bulk ation of materials such as iron and aluminum active layer The upper portion of a Gelisol volume of soil that is filled with air at any oxides and silicate clays. that is subject to freezing and thawing and is given time or under a given condition, such as abiotic Nonliving basic elements of the envi- underlain by permafrost. a specified moisture potential; usually the large ronment, such as rainfall, temperature, wind, active organic matter A portion of the soil pores.
organic matter that is relatively easily metabo- albic horizon A diagnostic subsurface accelerated erosion Erosion much more lized by microorganisms and cycles with a horizon from which clay and free iron rapid than normal, natural, geological erosion; half-life in the soil of a few days to a few years. oxides have been removed or in which the primarily as a result of the activities of humans adhesion Molecular attraction that holds the oxides have been segregated to the extent or, in some cases, of animals. surfaces of two substances (e., water and sand that the color of the horizon is determined acid cations Cations, principally Al3+, Fe3+, particles) in contact. primarily by the color of the primary sand and H+, that contribute to H+ ion activity either and silt particles rather than by coatings on adsorption The attraction of ions or com- these particles.
directly or through hydrolysis reactions with pounds to the surface of a solid. Soil colloids water. See also non-acid cations. adsorb large amounts of ions and water.
Alfisols An order in Soil Taxonomy. Soils acid rain Atmospheric precipitation with with gray to brown surface horizons, medium adsorption complex The group of organic to high supply of bases, and B horizons of pH values less than about 5.6, the acidity being and inorganic substances in soil capable of due to inorganic acids (such as nitric and sulfu- illuvial clay accumulation. These soils form adsorbing ions and molecules. mostly under forest or savanna vegetation in ric) that are formed when oxides of nitrogen and sulfur are emitted into the atmosphere.
aeration, soil The process by which air in climates with slight to pronounced seasonal the soil is replaced by air from the atmosphere. acid saturation The proportion or percent- In a well-aerated soil, the soil air is similar in age of a cation-exchange site occupied by acid algal bloom A population explosion of algae composition to the atmosphere above the soil. in surface waters, such as lakes and streams, cations. Poorly aerated soils usually contain more car- often resulting in high turbidity and green- or acid soil A soil with a pH value 6 7.
bon dioxide and correspondingly less oxygen red-colored water, and commonly stimulated Usually applied to surface layer or root zone, than the atmosphere above the soil. by nutrient enrichment with phosphorus and but may be used to characterize any horizon. aerobic (1) Having molecular oxygen as a nitrogen. See also reaction, soil.
part of the environment. (2) Growing only in alkaline soil Any soil that has pH 77. Usually acid sulfate soils Soils that are potentially the presence of molecular oxygen, as aerobic applied to the surface layer or root zone but extremely acid (pH 6 3.5) because of the pres- organisms. (3) Occurring only in the presence may be used to characterize any horizon or a ence of large amounts of reduced forms of sul- of molecular oxygen (said of certain chemical sample thereof.
See also reaction, soil. fur that are oxidized to sulfuric acid if the soils or biochemical processes, such as aerobic allelochemical An organic chemical by are exposed to oxygen when they are drained or decomposition). A sulfuric horizon containing the which one plant can influence another. See aerosolic dust A type of eolian material that allelopathy.
yellow mineral jarosite is often present. See also is very fine (about 1 to 10 µm) and may remain cat clays. allelopathy The process by which one plant suspended in the air over distances of thou- acidity, active The activity of hydrogen ions sands of kilometers. Finer than most loess.
may affect other plants by biologically active in the aqueous phase of a soil. It is measured chemicals introduced into the soil, either directly aggregate (soil) Many soil particles held in by leaching or exudation from the source plant, and expressed as a pH value. a single mass or cluster, such as a clod, crumb, or as a result of the decay of the plant residues. acidity, residual Soil acidity that can be neu- block, or prism.
The effects, though usually negative, may also be tralized by lime or other alkaline materials but agric horizon A diagnostic subsurface hori- positive. cannot be replaced by an unbuffered salt solution. zon in which clay, silt, and humus derived from allophane A poorly defined aluminosilicate acidity, salt replaceable Exchangeable hydro- an overlying cultivated and fertilized layer have mineral whose structural framework consists of gen and aluminum that can be replaced from an accumulated. Wormholes and illuvial clay, silt, short runs of three-dimensional crystals inter- acid soil by an unbuffered salt solution such as and humus occupy at least 5% of the horizon spersed with amorphous noncrystalline materials.
KCl or NaCl. Along with its more weathered companion, it is acidity, total The total acidity in a soil. It is agroforestry Any type of multiple crop- prevalent in volcanic ash materials. approximated by the sum of the salt-replaceable ping land-use that entails complementary rela- alluvial fan Fan-shaped alluvium deposited acidity plus the residual acidity.
tions between trees and agricultural crops. at the mouth of a canyon or ravine where debris- Actinomycetes A group of bacteria that agronomy A specialization of agriculture laden waters fan out, slow down, and deposit form branched mycelia that are thinner, but concerned with the theory and practice of their burden. 1This glossary was compiled and modified from several sources, including Glossary of Soil Science Terms [Madison, WI: Soil Science Society of America (1997)], Resource Conservation Glossary [Ankeny, IA: Soil Conservation Society of America (1982)], and Soil Taxonomy [Washington, DC: U. Department of Agriculture (1999)].
From the Glossary of Elements of the Nature and Properties of Soils, Third Edition, Nyle C. Copyright © 2010 by Pearson Education, Inc. Published by Pearson Prentice Hall. All rights reserved.
glossary alluvium A general term for all detrital mate- anion exchange capacity The sum total of arid climate Climate in regions that lack suf- rial deposited or in transit by streams, including exchangeable anions that a soil can adsorb. ficient moisture for crop production without gravel, sand, silt, clay, and all variations and Expressed as centimoles of charge per kilogram irrigation. In cool regions annual precipitation mixtures of these. Unless otherwise noted, allu- (cmolc /kg) of soil (or of other adsorbing mate- is usually less than 25 cm.
It may be as high as vium is unconsolidated. rial, such as clay). 50 cm in tropical regions. Natural vegetation is aluminosilicates Compounds containing anoxic See anaerobic.
aluminum, silicon, and oxygen as main con- anthropic epipedon A diagnostic surface Aridisols An order in Soil Taxonomy. Soils of stituents. An example is microcline, KAlSi3O8. horizon of mineral soil that has the same dry climates.
They have pedogenic horizons, amendment, soil Any substance other than requirements as the mollic epipedon but that low in organic matter, that are never moist for fertilizers, such as lime, sulfur, gypsum, and has more than 250 mg/kg of P2O5 soluble in as long as three consecutive months. They sawdust, used to alter the chemical or physical 1% citric acid, or is dry more than 10 months have an ochric epipedon and one or more of properties of a soil, generally to make it more (cumulative) during the period when not irri- the following diagnostic horizons: argillic, productive. The anthropic epipedon forms under natric, cambic, calcic, petrocalcic, gypsic, petr- long-continued cultivation and fertilization. ogypsic, salic, or a duripan.
amino acids Nitrogen-containing organic acids that couple together to form proteins. antibiotic A substance produced by one aspect (of slopes) The direction (e., Each acid molecule contains one or more amino species of organism that, in low concentra- south or north) that a slope faces with respect groups (—NH2) and at least one carboxyl group tions, will kill or inhibit growth of certain to the sun. In addition, some amino acids other organisms. association, soil See soil association.
Ap The surface layer of a soil disturbed by Atterberg limits Water contents of fine- Ammanox A biochemical process in the N cultivation or pasturing. grained soils at different states of consistency. cycle by which certain anaerobic bacteria or liquid limit (LL) The water content cor- apatite A naturally occurring complex cal- archaea oxidize ammonium ions using nitrite responding to the arbitrary limit between cium phosphate that is the original source of ions as the electron acceptor, the main product the liquid and plastic states of consistency most of the phosphate fertilizers. Formulas such being N2 gas.
as [3Ca3(PO4)2] · CaF2 illustrate the complex ammonification The biochemical process compounds that make up apatite. plastic limit (PL) The water content whereby ammoniacal nitrogen is released from corresponding to an arbitrary limit aquic conditions Continuous or periodic between the plastic and semisolid states of nitrogen-containing organic compounds.