Soil Survey Manual

Soil Science Division Staff

Agriculture Handbook No. 18

Soil Survey Manual

By Soil Science Division Staff

United States Department of Agriculture

Handbook No. 18

Issued March 2017

Minor Amendments February 2018

This manual is a revision and enlargement of 

U.S. Department of Agriculture Handbook No. 

18, the Soil Survey Manual, previously issued 

October 1962 and October 1993. This version 

supersedes both previous versions.
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 i

Table of Contents

List of Figures ................................................................................vii

List of Tables.................................................................................xvii

Introduction to the Fourth Edition......................................xxiii

Purpose ........................................................................................xxiii

Need for Additions and Revisions................................................ xxv

Online Access.............................................................................xxvii

Citation and Authorship..............................................................xxvii

Acknowledgements...................................................................xxviii

References.................................................................................xxviii

Chapter 1.—Soil and Soil Survey............................................. 1

Soil Survey—Definition and Description......................................... 1

Early Concepts of Soil...................................................................... 3

Early Development of Soil Classification ........................................ 7

Modern Concept of Soil ................................................................... 8

Development of Soil Taxonomy....................................................... 9

Scientific Foundation of Soil Survey.............................................. 10

Development of the Soil Survey in the U.S. .................................. 13

References...................................................................................... 18

Chapter 2.—Landscapes, Geomorphology, and Site 

Description................................................................................ 21

Introduction .................................................................................... 21

Capturing Soil-Landscape Relationships at Various Scales........... 25

Placing Soil-Landscape Relationships in Their Proper Context .... 28

Consistently Describing Landscapes, Landforms, and 

Geomorphology ....................................................................... 30

Parent Material ............................................................................... 53

Bedrock .......................................................................................... 66

Lithostratigraphic Units.................................................................. 69

Erosion............................................................................................ 70
ii Table of Conten

Land Cover..................................................................................... 77

Vegetation....................................................................................... 78

Ecological Sites.............................................................................. 79

Integrated Natural Resource Inventories........................................ 80

References...................................................................................... 80

Chapter 3.—Examination and Description of Soil 

Profiles........................................................................................ 83

Introduction .................................................................................... 83

General Terms Used to Describe Soils........................................... 84

Studying Pedons............................................................................. 87

Designations for Horizons and Layers........................................... 91

Near Surface Subzones................................................................. 114

Root-Restricting Depth................................................................. 118

Particle-Size Distribution ............................................................. 119

Soil Texture .................................................................................. 120

Rock Fragments and Pararock Fragments.................................... 131

Artifacts........................................................................................ 137

Compound Texture Modifiers....................................................... 140

Fragments on the Surface ............................................................. 141

Soil Color ..................................................................................... 145

Soil Structure................................................................................ 155

Internal Ped and Void Surface Features........................................ 163

Concentrations.............................................................................. 168

Pedogenic Carbonates ................................................................. 173

Redoximorphic Features............................................................... 177

Consistence................................................................................... 180

Roots............................................................................................. 193

Pores............................................................................................. 195

Animals ........................................................................................ 197

Selected Chemical Properties....................................................... 198

Soil Water..................................................................................... 205

Soil Temperature .......................................................................... 228

References.................................................................................... 230

Chapter 4.—Soil Mapping Concepts................................... 235

Soil Mapping Process................................................................... 235

Field Operation and Equipment ................................................... 241
Soil Survey Manual i

Soil Identification and Classification............................................ 245

Soil Map Units.............................................................................. 248

Kinds of Map Units...................................................................... 256

Minor Components Within Map Units......................................... 260

Designing and Documenting Map Units...................................... 262

Naming Map Units....................................................................... 265

Orders of Soil Surveys ................................................................. 268

Correlation Steps.......................................................................... 276

Quality Control and Quality Assurance........................................ 280

Records and Documentation ........................................................ 281

Soil Handbook.............................................................................. 284

Soil Maps Made by Other Methods ............................................. 289

Supporting Data............................................................................ 291

References.................................................................................... 292

Chapter 5.—Digital Soil Mapping......................................... 295

Principles and Concepts ............................................................... 295

Stages and Processes.................................................................... 299

Applications of Digital Soil Mapping .......................................... 341

Summary ...................................................................................... 346

References.................................................................................... 346

Chapter 6.—Tools for Proximal Soil Sensing ................. 355

Introduction .................................................................................. 355

Common Geophysical Methods................................................... 356

Less Common Proximal Sensing Methods .................................. 376

References.................................................................................... 387

Chapter 7.—Soil Survey Data Collection, 

Management, and Dissemination.................................. 395

Introduction .................................................................................. 395

Automated Data Processing in Soil Survey ................................. 396

Recording Data and Information—Field and Lab........................ 400

Soil Information Systems............................................................. 415

History of Soil Data Management in the U.S............................... 421

References.................................................................................... 432

Chapter 8.—Interpretations: The Impact of Soil 

Properties on Land Use..................................................... 433

Introduction .................................................................................. 433
iv Table of Conten

Interpretive Models ...................................................................... 436

Current U.S. Interpretive System ................................................. 440

Map Units and Soil Interpretations .............................................. 446

Interpretive Soil Properties........................................................... 449

Dynamic Soil Properties............................................................... 456

Interpretive Applications.............................................................. 457

Areal Application of Interpretations............................................. 475

References.................................................................................... 478

Chapter 9.—Assessing Dynamic Soil Properties 

and Soil Change.................................................................... 481

Importance of DSPs...................................................................... 481

How to Collect DSPs for Soil Survey .......................................... 483

Data Collection Plan..................................................................... 489

Analyzing Dynamic Soil Property Data....................................... 497

Summary of DSPs in Soil Survey ................................................ 501

References.................................................................................... 502

Chapter 10.—Subaqueous Soil Survey ............................. 505

Introduction .................................................................................. 505

Sampling, Description, Characterization, and Classification....... 506

Soil-Landscape Relationships ...................................................... 513

Survey Methods and Procedures.................................................. 516

Significance of Subaqueous Soil Information.............................. 519

References.................................................................................... 521

Chapter 11.—Human-Altered and HumanTransported Soils................................................................. 525

Introduction .................................................................................. 525

Background .................................................................................. 526

Importance.................................................................................... 531

Occurrence.................................................................................... 532

Identification................................................................................. 532

Description ................................................................................... 536

Survey Methods and Procedures.................................................. 537

Pedon Descriptions....................................................................... 549

References.................................................................................... 552

Appendix 1.—Official Soil Series Description................ 555

Olton Series.................................................................................. 555
Soil Survey Manual

Appendix 2.—Detailed Map Unit Description.................. 561

OcA—Olton clay loam, 0 to 1 percent slopes.............................. 561

Appendix 3.—NCSS Soil Characterization 

Database................................................................................... 563

Appendix 4.—Web Soil Survey ............................................. 573

Soil Survey Maps and Map Products........................................... 573

Index................................................................................................. 587

 vii

Chapter 1.— Soil and Soil Survey

No figures.

Chapter 2.—Landscapes, Geomorphology, and Site 

Description

Figure 2-1 ....................................................................................... 23

A talus cone in a canyon illustrating a distinct, sharp break between 

landforms.

Figure 2-2 ....................................................................................... 26

A scarp slope of a cuesta above an alluvial flat. 

Figure 2-3 ....................................................................................... 27

Diagram of the change of dominant surface fragment sizes and 

percentages along a transect of a scarp slope on a cuesta. 

Figure 2-4 ....................................................................................... 27

A comparison of digital maps with 60 x 60 m and 10 x 10 m grid 

sizes. 

Figure 2-5 ....................................................................................... 28

Images showing changes in slope class interpretation as affected by 

DEM resolution from LiDAR. 

Figure 2-6 ....................................................................................... 32

A canyonlands landscape in the San Rafael Swell, Utah.

Figure 2-7 ....................................................................................... 33

Loess hill and river valley landforms in western Iowa, along the 

Missouri River.

Figure 2-8 ....................................................................................... 34

Turf hummock microfeatures in a wet meadow in Oregon.

Figure 2-9 ....................................................................................... 39

A quarry as an example of an anthropogenic landform.

Figure 2-10 ..................................................................................... 40

Soil conservation terraces as an example of an anthropogenic 

microfeature.

Figure 2-11 ..................................................................................... 41

Effect of slope aspect on vegetation and tree seedling survival. 

List of Figures
viii List of Figu

Figure 2-12 ..................................................................................... 42

Simple versus complex slopes and slope positions. 

Figure 2-13 ..................................................................................... 43

Complex slopes on a hillslope of interbedded sedimentary rocks in 

Wildcat Hills, Nebraska.

Figure 2-14 ..................................................................................... 46

Slope shape based on combinations of surface curvature.

Figure 2-15 ..................................................................................... 47

Three-dimensional depiction of geomorphic components of hills.

Figure 2-16 ..................................................................................... 48

Three-dimensional depiction of geomorphic components of terraces 

and stepped landforms.

Figure 2-17 ..................................................................................... 49

Three-dimensional depiction of geomorphic components of 

mountains.

Figure 2-18 ..................................................................................... 50

Three-dimensional depiction of geomorphic components of flat 

plains.

Figure 2-19 ..................................................................................... 51

Water ponding in the microlows in an area of Vertisols that exhibits 

gilgai microfeatures. 

Figure 2-20 ..................................................................................... 51

Illustrations and descriptive terms for drainage patterns. 

Chapter 3.—Examination and Description of Soil 

Profiles

Figure 3-1 ....................................................................................... 89

A shallow soil pit with a face that has been cleaned and prepared 

for describing the soil profile. 

Figure 3-2 ....................................................................................... 90

A horizontal view of a fragipan from a soil in Tennessee. 

Figure 3-3 ....................................................................................... 98

A soil with a permanently frozen ice layer between depths of 60 and 

130 cm. 

Figure 3-4 ..................................................................................... 113

Examples of topography classes for horizon boundaries. 

Figure 3-5 ..................................................................................... 115

Five kinds of near surface subzones. 

Figure 3-6 ..................................................................................... 121

Relationships among particle-size classes of the USDA system and 

four other systems.
Soil Survey Manual 

Figure 3-7 ..................................................................................... 125

USDA textural triangle showing the percentages of clay, silt, and 

sand in the 12 basic texture classes.

Figure 3-8 ..................................................................................... 135

A soil in which the layers below a depth of about 20 cm are very 

cobbly loamy sand. 

Figure 3-9 ..................................................................................... 143

An area of bouldery soil (class 1).

Figure 3-10 ................................................................................... 143

An area of very bouldery soil (class 2).

Figure 3-11 ................................................................................... 144

An area of extremely bouldery soil (class 3).

Figure 3-12 ................................................................................... 144

An area of rubbly soil (class 4).

Figure 3-13 ................................................................................... 145

An area of very rubbly soil (class 5).

Figure 3-14 ................................................................................... 147

The arrangement of color chips according to value and chroma on 

the Munsell soil-color card of hue 10YR. 

Figure 3-15 ................................................................................... 148

A schematic diagram showing relationships among hue, value, and 

chroma in the Munsell color system. 

Figure 3-16 ................................................................................... 157

Examples of soil structure types.

Figure 3-17 ................................................................................... 158

Prismatic soil structure. 

Figure 3-18 ................................................................................... 159

Peds with angular blocky structure. 

Figure 3-19 ................................................................................... 163

Large reversible trans-horizon cracks extending from the soil 

surface deep into the subsoil of a clayey soil. 

Figure 3-20 ................................................................................... 164

Shiny clay films coating the surface of a ped. 

Figure 3-21 ................................................................................... 165

Sand grains coated and bridged with illuvial clay. 

Figure 3-22 ................................................................................... 166

Prominent slickensides in the Bss horizon of a Vertisol.

Figure 3-23 ................................................................................... 169

Masses of secondary calcium carbonate in the calcic horizon of an 

Aridisol.
x List of Figu

Figure 3-24 ................................................................................... 170

A soil with a reticulately mottled zone with plinthite below a depth 

of about 2 feet.

Figure 3-25 ................................................................................... 171

A cluster of gympsum crystals (selenite) in an Aridisol.

Figure 3-26 ................................................................................... 176

Schematic diagram of diagnostic carbonate morphology for 

the four main stages of carbonate accumulation in two 

morphogenetic sequences. 

Figure 3-27 ................................................................................... 179

Redoximorphic features consisting of a redox concentration as an 

iron mass and an iron depletion. 

Figure 3-28 ................................................................................... 190

A field test on a soil with a moderately fluid manner of failure class. 

Figure 3-29 ................................................................................... 206

Jarosite concentrations that formed due to oxidation in a drained 

marsh soil containing sulfides.

Figure 3-30 ................................................................................... 212

Model-based curve for a medium textured horizon and the 

relationship of water state class limits to water contents 

determined from the desorption curve.

Figure 3-31 ................................................................................... 224

Bulk density classes: low, medium, and high. 

Figure 3-32 ................................................................................... 225

Saturated hydraulic conductivity classes based on bulk density and 

texture relationships.

Chapter 4.—Soil Mapping Concepts

Figure 4-1 ..................................................................................... 242

A truck-mounted hydraulic probe. 

Figure 4-2 ..................................................................................... 243

A backhoe excavation and safety measures in deep trenches. 

Figure 4-3 ..................................................................................... 247

Illustration of polypedons. 

Figure 4-4 ..................................................................................... 258

Three images of an area that meets the definition of a soil complex. 

Figure 4-5 ..................................................................................... 259

Block diagram depicting the relationship of the soils in the 

Monona-Ida-Judson association in the general soil map of 

Woodbury County, Iowa. 

Figure 4-6 ..................................................................................... 277

Diagram illustrating soil correlation as a continuous process. 
Soil Survey Manual 

Chapter 5.—Digital Soil Mapping

Figure 5-1 ..................................................................................... 306

Comparison of spectral bands of common sensors to the reflectance 

spectra of common materials.

Figure 5-2 ..................................................................................... 320

Flow chart illustrating the general steps in selecting environmental 

covariates.

Figure 5-3 ..................................................................................... 322

Simplistic representation of sampling locations as determined by 

simple random, systematic, stratified random, and multistage 

random sampling designs.

Figure 5-4 ..................................................................................... 324

A comparison of the distribution of simple random, stratified 

random, and cLHS sampling methods over the data range of a 

slope gradient covariate.

Figure 5-5 ..................................................................................... 327

ISODATA unsupervised classification of both terrain and spectral 

data derivatives in eastern Emery County, Utah. 

Figure 5-6 ..................................................................................... 329

Simplistic representation of hard classification and fuzzy 

classification. 

Figure 5-7 ..................................................................................... 330

Supervised fuzzy classification of Landsat imagery for an area 

along the east shore of the Great Salt Lake, Utah. 

Figure 5-8 ..................................................................................... 332

Output from a hierarchical decision-tree knowledge-based 

classification for four classes. 

Figure 5-9 ..................................................................................... 333

Classification using random forests method for parent material 

classes in the Boundary Waters Canoe Area Wilderness, 

Minnesota. 

Figure 5-10 ................................................................................... 336

Interpolation using ordinary kriging of soil K concentration in the 

Salt Lake City Valley, Utah. 

Figure 5-11 ................................................................................... 341

Example of the confusion index for soil class prediction over 

approximately 300 km2 in the Powder River Basin, Wyoming. 

Figure 5-12 ................................................................................... 342

Example of prediction intervals and prediction interval width for 

soil depth to a restricting layer over approximately 50 km2 in 

San Juan County, Utah. 
xii List of Figu

Figure 5-13 ................................................................................... 343

Example of a disaggregation of SSURGO in West Virginia. 

Chapter 6.—Tools for Proximal Soil Sensing

Figure 6-1 ..................................................................................... 359

A typical GPR system. 

Figure 6-2 ..................................................................................... 360

A radar record showing well expressed spodic and argillic horizons 

in a Pomona soil in north-central Florida.

Figure 6-3 ..................................................................................... 361

A radar record showing a discontinuity separating a loamy eolian 

mantle from sandy glacial outwash in southern Rhode Island.

Figure 6-4 ..................................................................................... 362

A terrain-corrected radar record in which a water table provides a 

high-amplitude reflector in a dune field in Indiana.

Figure 6-5 ..................................................................................... 363

A radar record from an area of Freetown soils showing the 

thickness of organic soil materials that overlie coarse textured 

glacial outwash.

Figure 6-6 ..................................................................................... 367

Three of the commercially available ground conductivity meters 

used in soil investigations. 

Figure 6-7 ..................................................................................... 369

Spatial variations in ECa within the upper 150 cm of the soil 

profiles at a site in northern Texas. 

Figure 6-8 ..................................................................................... 369

Spatial variations in ECa within the upper 150 cm of five soils in 

northern Iowa. 

Figure 6-9 ..................................................................................... 371

Spatial distribution of ECa across a cultivated field in north-central 

Montana. 

Figure 6-10 ................................................................................... 373

A towed electrode-array soil ECa mapping system behind a utility 

vehicle in a field of corn stubble.

Figure 6-11 ................................................................................... 374

Maps of apparent conductivity prepared from shallow and deep 

data collected in west-central Illinois.

Figure 6-12 ................................................................................... 376

A common capacitively induced coupling resistivity system. 

Figure 6-13 ................................................................................... 376

A soil electrical conductivity depth profile from an agricultural test 

plot at Ohio State University. 
Soil Survey Manual xi

Figure 6-14 ................................................................................... 377

Magnetic surveying with a cesium vapor gradiometer integrated 

with a global positioning system receiver. 

Figure 6-15 ................................................................................... 380

A portable XRF spectrometer. 

Figure 6-16 ................................................................................... 382

A probe equipped with insertion load sensors and two 

spectrometers. 

Figure 6-17 ................................................................................... 383

A vehicle-mounted passive gamma-ray sensor.

Figure 6-18 ................................................................................... 386

A sampling mechanism for a towed system that simultaneously 

maps soil pH and apparent electrical conductivity.

Chapter 7.—Soil Survey Data Collection, 

Management, and Dissemination

Figure 7-1 ..................................................................................... 406

Standard pedon description form.

Figure 7-2 ..................................................................................... 413

Conceptual model showing the relationships and degree of 

generalization of data between different map scales and 

products. 

Figure 7-3 ..................................................................................... 416

An illustration of the increased number of users of NRCS’s Web Soil 

Survey application.

Chapter 8.—Interpretations: The Impact of Soil 

Properties on Land Use

Figure 8-1 ..................................................................................... 441

Membership function for slope percent for a limitation style 

interpretation. 

Figure 8-2 ..................................................................................... 443

Graphs representing the three basic suitability styles. 

Figure 8-3 ..................................................................................... 444

Diagram of a hypothetical parent rule for dwellings with 

basements. 

Figure 8-4 ..................................................................................... 476

A soil map showing the distribution of mapping units on the 

landscape and an interpretive map showing limitations for 

local roads and streets.

Figure 8-5 ..................................................................................... 479

Conceptual framework of raster-based soil interpretation.
xiv List of Figu

Chapter 9.—Assessing Dynamic Soil Properties 

and Soil Change

Figure 9-1 ..................................................................................... 483

Relationship between soil functions and some dynamic soil 

properties. 

Figure 9-2 ..................................................................................... 488

A generalized cross-section of a soil landscape near Olivia, 

Minnesota. 

Figure 9-3 .................................................................................... 491

Documentation from the Georgia Longleaf Pine Dynamic Soil 

Property project. 

Figure 9-4 ..................................................................................... 492

Example of pedon placement for a paired site in Dodge County, 

Nebraska. 

Figure 9-5 ..................................................................................... 493

Example of detailed plot sampling instructions for a rangeland DSP 

project in Utah. 

Figure 9-6 ..................................................................................... 498

Dynamic soil property data in relation to ecological sites, soil 

interpretations, and monitoring data. 

Figure 9-7 ..................................................................................... 500

 Dynamic soil properties of 0–2 cm samples for two DSP projects 

for soil organic carbon measured as total carbon and water 

stable aggregates. 

Chapter 10.—Subaqueous Soil Survey

Figure 10-1 ................................................................................... 508

A pontoon boat used for subaqueous soil sampling. 

Figure 10-2 ................................................................................... 509

Equipment for vibracore sampling. 

Figure 10-3 ................................................................................... 510

A core barrel and core catcher. 

Figure 10-4 ................................................................................... 511

A core from subaqueous sampling. 

Figure 10-5 ................................................................................... 512

Incubation pH for three horizons from a Fluventic Sulfiwassent. 

Figure 10-6 ................................................................................... 514

Examples of subaqueous landscape units across a coastal lagoon.

Figure 10-7 ................................................................................... 515

Soil-landscape relationships across a coastal lagoon in Rhode 

Island and Connecticut.
Soil Survey Manual 

Figure 10-8 ................................................................................... 519

GPR output for a freshwater lake with thick organic materials. 

Chapter 11.—Human-Altered and HumanTransported Soils

Figure 11-1 ................................................................................... 527

Landfill complex in Virginia. 

Figure 11-2 ................................................................................... 528

Machu Picchu, Peru. 

Figure 11-3 ................................................................................... 529

Profile of the Laguardia soil series showing artifacts in multiple 

deposits of human-transported material. 

Figure 11-4 ................................................................................... 530

An ancient Roman urban anthroscape. 

Figure 11-5 ................................................................................... 533

McMurdo Station, Antarctica. 

Figure 11-6 ................................................................................... 551

A profile of the Ladyliberty soil series. 

Appendix 1.—Official Soil Series Description

Figure A-1..................................................................................... 560

Profile of the Olton series.

Appendix 2.—Detailed Map Unit Description

No figures.

Appendix 3.—NCSS Soil Characterization Database

No figures.

Appendix 4.—Web Soil Survey

Figure A-2..................................................................................... 574

Soil map showing an area of interest on the Southern High Plains of 

western Texas and eastern New Mexico. 

Figure A-3..................................................................................... 574

The map legend and conventional symbols found on soil maps.

Figure A-4..................................................................................... 579

Map showing land capability class.

Figure A-5..................................................................................... 580

Map showing hydrologic soil groups. 

Figure A-6..................................................................................... 581

Map showing ecological sites. 

Figure A-7..................................................................................... 582

Shortgrass/blue gramma dominant community of the Deep 

Hardland ecological site (R077CY022TX). 
xvi List of Figu

Figure A-8..................................................................................... 583

State-and-transition model showing pathways and causes of change 

in the plant communities.
 xvii

Chapter 1.—Soil and Soil Survey

No tables.

Chapter 2.—Landscapes, Geomorphology, and Site 

Description

Table 2-1......................................................................................... 31

Physiographic Location, Relative Scale (in Descending 

Order) and Examples in the U.S.

Table 2-2......................................................................................... 35

Prominent Geomorphic Environments and Processes in 

the U.S. and Examples

Table 2-3......................................................................................... 44

Definitions of Slope Classes

Table 2-4......................................................................................... 47

Geomorphic Component Terms for Hills

Table 2-5......................................................................................... 48

Geomorphic Component Terms for Terraces and 

Stepped Landforms

Table 2-6......................................................................................... 49

Geomorphic Component Terms for Mountains

Table 2-7......................................................................................... 50

Geomorphic Component Terms for Flat Plains

Table 2-8......................................................................................... 62

Types of Landslide Deposits 

Table 2-9......................................................................................... 64

General Groups of Parent Materials Based on 

Geomorphic Process or Setting

Table 2-10....................................................................................... 69

Lithostratigraphic Units and Their Hierarchical Rank 

and Definition

Table 2-11....................................................................................... 71

Kinds of Accelerated Erosion

List of Tables
xviii List of Tabl

Table 2-12....................................................................................... 76

Degree Classes for Accelerated Soil Erosion 

Chapter 3.—Examination and Description of Soil 

Profiles

Table 3-1....................................................................................... 126

General Soil Texture Groups

Table 3-2....................................................................................... 134

Terms for Rock Fragments and Pararock Fragments

Table 3-3....................................................................................... 135

Guide for Determining Rock Fragment Modifier of 

Texture for Soils with a Mixture of Rock Fragment 

Sizes

Table 3-4....................................................................................... 142

Classes of Surface Stones and Boulders in Terms of 

Cover and Spacing

Table 3-5....................................................................................... 153

Color Contrast Class Terms and Their Criteria

Table 3-6....................................................................................... 160

Size Class Terms for Peds with Various Soil Structure 

Types

Table 3-7....................................................................................... 183

Rupture Resistance Classes for Blocklike Specimens

Table 3-8....................................................................................... 185

Rupture Resistance Classes Applied to Crushing PlateShaped Specimens

Table 3-9....................................................................................... 186

Plasticity Classes

Table 3-10..................................................................................... 186

Toughness Classes

Table 3-11..................................................................................... 187

Stickiness Classes

Table 3-12..................................................................................... 188

Manner of Failure Classes

Table 3-13..................................................................................... 191

Penetration Resistance Classes

Table 3-14..................................................................................... 192

Excavation Difficulty Classes
Soil Survey Manual x

Table 3-15..................................................................................... 199

Reaction Class Terms and Their Ranges in pH

Table 3-16..................................................................................... 200

Effervescence Class Terms

Table 3-17..................................................................................... 202

Salinity Class Terms

Table 3-18..................................................................................... 207

Frequency and Duration of Inundation Classes 

(Flooding or Ponding)

Table 3-19..................................................................................... 209

Water State Classes

Table 3-20..................................................................................... 215

Classes of Internal Free Water

Table 3-21..................................................................................... 216

Example of a Water State Annual Pattern

Table 3-22..................................................................................... 221

Classes of Saturated Hydraulic Conductivity 

Table 3-23..................................................................................... 222

Saturated Hydraulic Conductivity Class Limits in 

Equivalent Units

Chapter 4.—Soil Mapping Concepts

Table 4-1....................................................................................... 250

Kinds of Map Unit Components Used in Soil Survey

Table 4-2....................................................................................... 254

Miscellaneous Areas Used as Map Unit Components

Table 4-3....................................................................................... 267

Phases Most Commonly Used in Naming Soil Map 

Units

Table 4-4....................................................................................... 270

Key for Identifying Orders of Soil Surveys

Table 4-5....................................................................................... 281

Major Applications of Soil Survey Standards

Chapter 5.—Digital Soil Mapping

Table 5-1....................................................................................... 312

Selected Primary and Compound Terrain Attributes 

Used in Digital Soil Mapping
xx List of Tabl

Table 5-2....................................................................................... 315

Spectral Band Ratios Used in Digital Soil Mapping 

Table 5-3....................................................................................... 338

Confusion Matrix of Three Modeled Soil Subgroup 

Classes

Chapter 6.—Tools for Proximal Soil Sensing

Table 6-1....................................................................................... 357

Methods of Proximal Soil Sensing and Their Primary

Application in Soil Survey

Chapter 7.—Soil Survey Data Collection, 

Management, and Dissemination

No tables.

Chapter 8.—Interpretations: The Impact of Soil 

Properties on Land Use

Table 8-1....................................................................................... 438

Interpretive Soil Properties and Limitation Classes for 

Septic Tank Absorption Fields

Table 8-2....................................................................................... 439

Values of Applicable Interpretive Properties for Septic 

Systems for an Aksarben Component

Table 8-3....................................................................................... 477

Limitation Ratings for Local Roads and Streets for the 

Albrights Map Unit (AbB)

Chapter 9.—Assessing Dynamic Soil Properties 

and Soil Change

Table 9-1....................................................................................... 493

DSP Project Data Elements Collected at Site (Across 

Plot) Scales

Table 9-2....................................................................................... 494

DSP Project Data Elements Collected at Pedons; 

Multiple Locations per Site/Plot

Table 9-3....................................................................................... 496

Measurements of Dynamic Soil Properties on 

Individual Samples

Chapter 10.—Subaqueous Soil Survey

No tables.
Soil Survey Manual x

Chapter 11.—Human-Altered and HumanTransported Soils

Table 11-1..................................................................................... 543

Soil Taxonomy Subgroups and HAHT Soil Concepts

Table 11-2..................................................................................... 544

Soil Taxonomy Family Terms and HAHT Soil 

Concepts

Appendix 1.—Official Soil Series Description

No tables.

Appendix 2.—Detailed Map Unit Description

No tables.

Appendix 3.—NCSS Soil Characterization 

Database

Table A-1 ...................................................................................... 564

Primary Characterization Data

Table A-2 ...................................................................................... 570

Supplementary Characterization Data

Appendix 4.—Web Soil Survey

Table A-3 ...................................................................................... 575

Map Unit Symbols and Names Displayed on the Soil 

Map for the Area of Interest

Table A-4 ...................................................................................... 576

Aggregation Methods 

Table A-5 ...................................................................................... 584

Engineering Properties and Classifications

Table A-6 ...................................................................................... 585

Soil Chemical Properties

 xxiii

Introduction to the Fourth Edition

By Craig Ditzler, Kenneth Scheffe, and H. Curtis Monger, 

USDA–NRCS.

The Soil Survey Manual, USDA Handbook No. 18, provides the 

major principles and practices needed for making and using soil surveys 

and for assembling and using related data. The term “soil survey” is used 

here to encompass the process of mapping, describing, classifying, and 

interpreting natural three-dimensional bodies of soil on the landscape. 

This work is performed by the National Cooperative Soil Survey in the 

United States and by other similar organizations worldwide. The Manual 

provides guidance, methodology, and terminology for conducting a 

soil survey but does not necessarily convey policies and protocols 

required to administer soil survey operations. The soil bodies contain 

a sequence of identifiable horizons and layers that occur in repeating 

patterns in the landscape as a result of the factors of soil formation as 

described by Dokuchaev (1883) and Jenny (1941). Soil scientists gain 

an understanding of the factors of soil formation in their area, along with 

the resulting expression of their interaction in the soil, and are then able 

to make maps of the natural soil bodies quite efficiently (Hudson, 1992). 

The maps of soil bodies are related to, but different from, maps of single 

soil properties, such as organic matter or pH. The latter are made by 

sampling and statistical modeling to show how these properties vary over 

the landscape.

Purpose

The Manual is intended primarily for use by soil scientists engaged 

in the work of making soil surveys. It is an especially important reference 

for soil scientists early in their careers as they learn the many complex 

aspects of making a soil survey. It is also an important reference for 

experienced soil surveyors who want to review the details regarding 

many of the standards used in soil survey. For example, chapter 3, 

“Examination and Description of Soil Profiles,” contains the accepted 
xxiv Introduc

terms and definitions for specific soil properties that are used when 

describing soil profiles in the field. It also contains extensive information 

describing each soil property and the proper procedures for observing 

or measuring it in the field. The Manual is therefore an important 

companion to other soil survey references, such as the National Soil 

Survey Handbook (USDA-NRCS, 2016), the Field Book for Describing 

and Sampling Soils (Schoeneberger and Wysocki, 2012), and the Keys to 

Soil Taxonomy (Soil Survey Staff, 2014).

Although the Manual is oriented to the needs of those actively 

engaged in preparing soil surveys, workers and students who have limited 

soil science experience or are less familiar with the soil survey process 

can also use the information. Teachers, researchers, and students of soil 

science and related disciplines, especially those interested in pedology, 

soil morphology, soil geography, ecology, geomorphology, and the 

science underlying soil survey, will find this manual useful. Resource 

specialists, such as wetland scientists, foresters, and agronomists, and 

others who use soil surveys in their work, can refer to the Manual to 

better understand how soil surveys are made and how to interpret the 

technical information they provide. Parts of the Manual, especially those 

concerning the description of soils in the field and the soil properties 

considered when predicting soil behavior under a specific use, have 

been adopted by private-sector soil scientists as standards. The Soil 

Survey Manual has proven to be an important source of information for 

government agencies, nongovernmental organizations, and private-sector 

resource specialists in other countries involved in soil survey projects. 

Because the Manual describes all facets of the soil survey process, it is 

an important guide for developing proposals to conduct soil surveys and 

to create detailed plans for projects in other parts of the world.

The Manual serves as the guiding document for activities of the 

National Cooperative Soil Survey (NCSS), a cooperative undertaking led 

by the United States Department of Agriculture. The NCSS includes other 

Federal and State agencies, universities, non-governmental organizations, 

and private-sector soil scientists interested in making soil surveys and/

or interpreting and using soil survey information. The original Federal 

authority for the Soil Survey of the United States is contained in the 

record of the 53rd Congress, Chapter 169, Agricultural Appropriations 

Act of 1896. The authority was elaborated in Public Law 74-46, the Soil 

Conservation Act of April 27, 1936, and again in Public Law 89-560, Soil 

Surveys for Resource Planning and Development, September 7, 1966. 

The Manual is the primary reference on the principles and technical 

details used by the local, State, and Federal contributors to soil surveys 

authorized under these acts.
Soil Survey Manual x

Need for Additions and Revisions

Since the third edition (1993) of the Manual was printed, significant 

changes have occurred that affect the ways soil surveys are made. In 

the United States, greater emphasis is now placed on the maintenance 

and modernization of previously completed soil surveys. Because of this, 

some soil scientists are now evaluating and improving existing surveys 

rather than making new soil surveys. The wide application of computer 

technology, in both the office and the field, has led to a proliferation 

of electronic data sources, including digital elevation models (DEMs), 

Light Detection and Ranging (LiDAR), digital geology maps and 

vegetation maps, and multi-spectral remote sensing data. The electronic 

data sources, combined with computer models that capture and apply 

knowledge of the interaction of the soil-forming factors, have allowed 

soil scientists to partially, and in a few cases totally, automate the soil 

mapping process. This has had an important impact on the scientist’s 

ability to formalize and document the soil-landscape models used to 

produce soil survey maps. It has also led to improved consistency in 

the maps produced using these methods. In addition, tools used for 

proximal sensing of soil properties, such as ground-penetrating radar and 

electromagnetic induction, have been increasingly used in special soil 

survey field studies. Greater attention is also being given to recognizing 

anthropogenic influences on soils. This has resulted in a need for the 

development of new standards for horizon nomenclature for humanaltered soils, new terminology for describing human-made materials 

(artifacts) in soil profiles, and new classification groups. Soil surveys 

have also been conducted to a greater extent in shallow water (subaquatic) 

environments. New field procedures, descriptive terms, and taxonomic 

classes have been developed for conducting this innovative work.

Because of these changes, a major revision of the Manual was 

considered essential. Many parts have been revised, some parts have 

been extensively rewritten, and some new sections have been added. 

Entirely new subject matter in this edition of the Soil Survey Manual 

includes:

• Chapter 5, “Digital Soil Mapping.” This chapter presents many 

concepts and principles that have been developed regarding the 

use of computers and digital technology to aid in the making of 

soil surveys. 

• Chapter 6, “Tools for Proximal Soil Sensing.” This chapter 

covers recent advances in the use of noninvasive tools for rapidly 

collecting information about soil properties. 
xxvi Introduc

• Chapter 9, “Assessing Dynamic Soil Properties and Soil Change.” 

This chapter provides important information for documenting 

key soil properties, particularly in the near surface layers that are 

significantly impacted by soil management practices.

• Chapter 10, “Subaqueous Soil Survey.” This chapter covers the 

emerging specialized field of making soil surveys in shallow 

water environments. This work is proving to be highly valuable to 

resource managers, especially in coastal estuarine environments. 

• Chapter 11, “Human-Altered and Human-Transported Soils.” 

This chapter provides valuable guidance on making soil surveys 

in environments heavily impacted by humans. Examples include 

urban areas, mined sites, and drastically changed soils used for 

agriculture.

• Appendices. The new appendices reflect the current form and 

content of web-accessible soil survey information in the United 

States. They are cross referenced in various places throughout 

the text.

Other significant revisions include:

• The former chapter 3 (“Examination and Description of Soils”) is 

now split into two chapters: “Landscapes, Geomorphology, and 

Site Description” (chapter 2) and “Examination and Description 

of Soil Profiles” (chapter 3). This effectively separates the 

details for describing landscapes, geomorphology, and local 

site characteristics from the details for describing individual 

soil profiles. Both chapters incorporate all of the changes and 

additions to standard technical terms and their definitions that 

have been adopted by the National Cooperative Soil Survey 

since the previous publication of the Manual.

• The former chapters 2 (“Soil Systematics”) and 4 (“Mapping 

Techniques”) are combined and revised into a new chapter 4, 

“Soil Mapping Concepts.” Information in the previous edition 

on procedures that have since become obsolete or nearly so (such 

as the use of stereoscopes and aerial photo pairs to visualize 

landforms in three dimensions, “color checking” to manually 

inspect maps for proper joining of units, and use of dot-grids to 

determine the aerial extent of map units) has been omitted.

• The former chapters 5 (“Information Recording and Management”) and 7 (“Disseminating Soil Survey Information”) 

are revised and updated into the new chapter 7, “Soil Survey 

Data Collection, Management, and Dissemination.” The new 

chapter discusses the use of computer databases to effectively 
Soil Survey Manual xxv

store and manage soil survey information as well as provide 

information to end users. It also includes a historical summary 

of the development of the National Soil Information System 

(NASIS) in the United States. The summary may be useful to 

those outside the U.S. who are considering the development of a 

similar database.

• The former chapter 6 (“Interpretations”) is revised and updated 

into the new chapter 8 (“Interpretations: The Impact of Soil 

Properties on Land Use”). The new chapter describes some 

of the latest strategies for making current interpretations 

more quantitative and providing interpretive information for 

anticipated uses. 

Online Access

Given the rapid pace of technological change, flexibility is needed 

to provide information in a timely manner. In addition to a bound, hardcopy version of the Soil Survey Manual, a web-based version is also 

provided. The electronic version has convenient access and distribution 

of the information, and it affords users the option to “print on demand” 

individual parts or the entire document. The user can view each section 

of the Manual as a stand-alone chapter or view the entire document. The 

sections are arranged to correspond to the approximate chronological 

order of the work required to complete a soil survey. The reader has 

the choice of focusing on individual parts of interest or exploring the 

larger picture of conducting a soil survey project from beginning to 

end. Additional supplementary information not provided in the printed 

version will be included with the electronic version.

Citation and Authorship

The previous edition of the Soil Survey Manual (Soil Survey Division 

Staff, 1993) simply listed the author as the Soil Survey Division Staff. The 

contents of the Manual represented the collective contributions of many 

people over several decades. The new edition continues to recognize the 

innumerable past contributors by including the Soil Science Divison Staff 

as an author for chapters that retain significant portions of the previous 

publication. These chapters contain information that has been used for 

decades as well as new information related to improved methods and/

or new terminology. For the updated chapters, authors responsible for 
xxviii Introduc

revisions are listed in addition to the Soil Science Division Staff. For 

entirely new chapters, only individual contributing authors are cited by 

name. Technical content of the Manual was revised and edited by Craig 

Ditzler, Kenneth Scheffe, and H. Curtis Monger. English content was 

revised and edited by Jennifer Sutherland and Aaron Achen.

Recommended Citations

For individual chapters, provide authors and chapter title. For 

example:

Adamchuk, V.I., B. Allred, J. Doolittle, K. Grote, and R.A. Viscarra 

Rossel. 2017. Tools for proximal soil sensing. In C. Ditzler, K. Scheffe, 

and H.C. Monger (eds.) Soil survey manual, USDA Handbook 18, 

Government Printing Office, Washington, D.C., pp. 355–394. 

For the complete manual:

Soil Science Division Staff. 2017. Soil survey manual. C. Ditzler, K. 

Scheffe, and H.C. Monger (eds.). USDA Handbook 18. Government 

Printing Office, Washington, D.C.

Acknowledgements

The following individuals provided valuable assistance in the 

development and review of this edition of the Manual: Tim Warner, West 

Virginia University; Colby Brungard, New Mexico State University; 

Katey Yoast, USDA Food and Nutrition Service; Christopher Dorian, 

private consultant; and Natural Resource Conservation Service employees 

W. Dwain Daniels, Tony Jenkins, Dylan Beaudette, Julie Baker, Tammy 

Umholtz, Robert Long, Thomas D’Avello, Travis Nauman, Jessica 

Philippe, and Stephen Roecker.

Seminal contributions were made during the 1954 to 1977 era of 

field-based soil-geomorphic research projects in Iowa, New Mexico, 

North Carolina, Oregon, and West Texas. These projects were sponsored 

by the SCS Soil Survey Investigations Division (SSI) under the direction 

of G.D. Smith. SCS-SSI scientists who investigated fundamental soilgeomorphic principles in these projects included geologists R.V. Ruhe, 

J.W. Hawley, and C. Balster and pedologists L.H. Gile, R.B. Grossman, 

F.F. Peterson, R.B. Daniels, E. Gamble, J.E. Witty, W.C. Lynn, W.D. 

Nettleton, and R. Parsons.
Soil Survey Manual xx

References

Dokuchaev, V.V 1883. Russian chernozem. (Translated from Russian 

by N. Kaner, 1967.) Available from U.S. Department of Commerce, 

Clearinghouse for Federal Scientific and Technical Information, 

Springfield, VA.

Hudson, B.D. 1992. The soil survey as a paradigm-based science. Soil 

Science Society of America Journal 56:836-841.

Jenny, Hans. 1941. Factors of soil formation: A system of quantitative 

pedology. McGraw Hill Book Company, New York, NY.

Schoeneberger, P.J., and D.A. Wysocki. 2012. Geomorphic Description 

System, version 4.2. USDA Natural Resources Conservation Service, 

National Soil Survey Center, Lincoln, NE.

Soil Survey Division Staff. 1993. Soil survey manual. U.S. Department of 

Agriculture Handbook 18. Natural Resources Conservation Service.

Soil Survey Staff. 2014. Keys to soil taxonomy, 12th edition. USDA 

Natural Resources Conservation Service.

U.S. Department of Agriculture, Natural Resources Conservation Service. 

National soil survey handbook, title 430-VI. http://www.nrcs.

usda.gov/wps/portal/nrcs/detail/soils/ref/?cid=nrcs142p2_054242 

[Accessed 22 August 2016]