Historical Highlights in Soil Genesis, Morphology, and Classification1

M. G. CLINE2

ABSTRACTAlthough E. W. Hilgard and G. N. Coffey pioneered, it remained

for C. F. Marbut to integrate concepts in a comprehensive model ofsoil that found acceptance in America. Establishment of the Soil Sur-vey by the controversial Milton Whitney created a major instrumentfor progress in the subject matter of Division S-V. The Soil Surveyresponded to the philosophies of Marbut and survived a bitter con-troversy during the early years of the USDA Soil Conservation Ser-vice.

Division S-5 originated as an association of soil survey workers in1920. The association gradually broadened its scope from primaryconcern with soil survey affairs to include most elements of soilscience. In 1936 it merged with the Soils Section of ASA as the SoilScience Society of America, with its Division S-V responsible for thesubject matter of the original association.

The approaches to soil morphology, genesis, and classification havebeen dominated by requirements of the soil survey. From largely qual-itative concepts, the work has progressed to the quantitative ap-proaches characterized by the Soil Survey Manual of 1951 and SoilTaxonomy of 1975. Increased awareness of geomorphic history hasmade age a much more important element in concepts of genesis. Thequantitative limits of Soil Taxonomy have focused attention on the het-erogeneity of mapping units. The greatly increased amount of dataand modern data processing methods promise major opportunities foradvances in soil genesis and soil interpretation.

Additional Index Words: soil survey, soil province, geomorphology,soil taxonomy, soil conservation, factors of soil formation, soil in-terpretation.

INVITATION to present this paper suggested that itA should not only provide perspective of the develop-

ment of subject matter and the origins of Division S-5 (V),but also highlight prominent personalities of the past, in-cluding controversies that surrounded some of them. Theauthor has attempted to conform to these guidelines.

HILGARD AND THE EARLY YEARSIt is appropriate to start with Eugene Waldemar Hilgard.

He was born in Germany, raised on a farm in Illinois, andeducated in Europe as a geologist and chemist. He was agiant among the pioneers of soil science as well as a geolo-gist, chemist, agriculturalist, and scholar. Serious studentsof soil science should read Dr. Jenny's (8) appraisal of theman and his accomplishments, first in Mississippi(1855-73), briefly in Michigan (1873-75), and finally inCalifornia (1875-1906). It will suffice here to say that be-tween 1860 and the turn of the century Hilgard had enun-ciated or inferred most of the ideas about soil and its forma-tion that were the foundations of the Russian concepts ofsoil formulated late in the same period. Yet it remained forMarbut during the 1920's to present a model of soil, whichhe attributed to the Russian school, that had real impact in

1 Contribution from the Dep. of Agronomy, Cornell Univ. Ithaca, NY14853, as Agron. Pap. no. 1182. Bicentennial address presented beforeDiv. S-5, Soil Science Society of America, 29 Nov. 1976, in Houston,Texas. Received 22 Sept. 1975. Approved 23 Nov. 1976.

2 Professor Emeritus, Cornell Univ; Dep. of Agronomy, Bradfield &Emerson Halls, Cornell Univ., Ithaca, NY 14853.

America. One must wonder why Hilgard's contributions toour subject had so little impact. Although many of Hilgard'sideas were fundamental elements in Marbut's concepts,Hilgard apparently failed, where Marbut succeeded, in con-veying a comprehensive picture of how those ideas fittogether to explain the character of soils and differencesamong them.

WHITNEY AND THE SOIL SURVEYIn 1890 Milton Whitney emerged as an agressive, tough-

minded young professor in South Carolina. From thebeginning, he held firmly to a thesis that physical soilproperties related to moisture are primary controlling fac-tors in crop production, almost to the exclusion of soil fertil-ity and chemistry as important considerations. Hilgard wasmildly critical from the beginning. Whitney advanced toMaryland in 1892 and then became the first head of theDivision of Agricultural Soils in the Weather Bureau ofUSDA in 1894 and Chief of the new Bureau of Soils in1901. Hilgard took increasing exception to Whitney's viewsas time went on. It was not, however, until 1903 whenWhitney and Cameron published a major bulletin reiteratingWhitney's beliefs that "bedlam broke loose" (8, p. 96).This became one of the major controversies in soil science.It literally consumed Hilgard emotionally in his later years,aggravated perhaps by Whitney's intrusion into Hilgard'spersonal domain of the arid parts of western United States.

It was Whitney's trip in 1897 through the arid west thatmay have prompted establishment of the Soil Survey. Jenny(8, p. 93) reports that a year later a member of Whitney'sstaff was sent to Montana to try instruments for testing soilsof the arid regions. He constructed a "detailed, large-scalealkali map" of an area near Billings. Whitney is reported tohave been greatly impressed with the potential of that map,because it showed the character of soils in areas smallenough to be meaningful to individual farmers. The follow-ing year, the Division embarked on a program of soil sur-veys at a scale of 1 inch to 1 mile. This stands as Whitney'slasting monument. This event as well as Whitney himselfmerit special attention because morphology, genesis, andclassification of soils in America have been inextricably in-tertwined with the Soil Survey since its inception. Our dis-cipline has derived much of its impetus from the Survey,and it has provided a foundation in public service that hassustained much of our support.

The prevailing geologic concepts of soil and Whitney'scontroversial philosophy are both evident in the character ofmapping units and their "classification" in the early years.Readers are referred to US Bureau of Soils Bulletin 15,Soils of the United States by Whitney in 1909 (15) andBulletin 96 of the same title by Marbut et al. in 1913 (11).The United States was divided into 13 "provinces" and"regions." Both were essentially broad physiographic unitsdifferentiated on the basis of geographic features rather thansoil character (11, p. 7). Groups of soils, called soil series,were distinguished within provinces and regions on thebasis of color, character of subsoil, broadly similar relief

250

CLINE: HIGHLIGHTS IN SOIL GENESIS, MORPHOLOGY, AND CLASSIFICATION 251

and drainage, and origin (11, p. 8). Soil series were sub-divided into types, which were the mapping units, on thebasis of texture. The scheme was hierarchal only to the ex-tent that types were subdivisions of series and series wereconfined to single provinces or regions.

COFFEY AND MARBUTOne must mention G. N. Coffey of the Bureau of Soils as

an outstanding scientist whose ideas were far advanced, butlargely ignored during the early days of the Soil Survey. Hisbulletin, A Study of Soils of the United States, in 1913 (5)contains a remarkable section on alternative approaches tosoil classification. It describes the Russian work, although"discovery" of the Russian literature is commonly attrib-uted to Marbut. Coffey concluded that an ideal classifica-tion should be a hierarchal system based on inherent dif-ferences in the soil itself as "a natural body having adefinite genesis and distinct nature of its own and occupyingan independent position in the formations constituting thesurface of the earth" (5, p. 34). Like Hilgard, Coffey hasbeen given far too little credit for foresight in our field.

One need not dwell on the contributions of C. F. Marbut,who was described by Jenny (8, p. 73) as "the thinker withthe captivating smile." He began his professional career inMissouri in much the same manner as Hilgard in Missis-sippi 40 years earlier (12, p. 15). He credited the Russianschool with the bases for his concepts, yet he clearly knewHilgard's work. He was contemporary with Coffey in the"Bureau" from 1910 and must have known his philosophy.He obviously learned much from Whitney's ideas and hegained broad personal perspective from his own work in theSurvey. It has been suggested elsewhere (4) that his con-cepts were molded by Davis' ideas of geomorphology. Hemust have drawn on all of these sources and others. His ge-nius seems to have been ability to synthesize ideas in anorganized model of soil that brought order to the thinking ofother people. His "scheme for soil classification" presentedat the First International Congress of Soil Science in 1927(10) gave soil scientists world-wide an abstract of thatmodel and marked him as a leader in the field.

DEVELOPMENT OF DIVISION S-SLet us turn now to events and people that relate more

closely to the history of this division. As the Soil Surveygrew and increasing numbers of workers in the states aswell as the "Bureau" became involved, communicationamong workers and federal-state relationships deteriorated.On February 7, 1920, representatives of a number of statesof the upper Mississippi Valley met in Chicago and foundedthe American Association of Soil Survey Workers to coun-teract these trends. The first annual meeting was held at theUniversity of Chicago on November 19 and 20, 1920, withA. R. Whitson of the University of Wisconsin presiding asfirst president. Fifty-five members paid dues of $3.00 each,but with only $7.20 expenses and a balance of $157.80,dues were reduced to $1.00 at the first meeting. Bulletin 1(1) recording the proceedings was issued in mimeographedform at no charge as a contribution of the University of Wis-consin. This was the beginning of our organization.

That first meeting was devoted to papers and reports on

soil survey experiences, uses, techniques, laboratory work,and supporting legislation. M. F. Miller, a staunch sup-porter of soil surveys and later Dean of Agriculture at theUniversity of Missouri, was emphasizing uses of soil maps.M. M. McCool of Michigan State College was concernedwith soil water, which in his words "largely controls pro-ductivity" (shades of Milton Whitney). T. M. Bushnell ofTexas, later at Purdue to become the champion of the catenaconcept and of aerial photography, was describing a newand better odometer for traversing with Ford automobiles.Conrey of Ohio, Schoenmann of Michigan, and Condra ofNebraska were among participants who remained prominentover succeeding years. Marbut dominated the discussionperiods, and at the second meeting in 1921, presented hisfirst major paper on soil classification (9). In this paper, hepresented the germ of the concept of Pedocals and Pedal-fers, though not in these terms, and specifically rejectedWhitney's soil provinces as bases of soil classification.

The bulletins of the Association from 1921 to 1935record the trends in concerns of the Soil Survey and in ideasabout morphology, genesis, and classification in America.W. E. Hearn, W. E. McLenden, M. H. Lapham, and T. D.Rice reported as "Inspectors" of the Bureau of Soils, link-ing the field to Marbut (later Kellogg). H. H. Bennett, whowas to father the Soil Conservation Service and ignite themost furious controversy of the Soil Survey, was a promi-nent contributor. C. F. Shaw, "a Whitney man" (8, p. 102)represented California and focused on classification accord-ing to age relationships of soils in that State. His ideas con-tinued to conflict with Marbut's scheme in later years. R. S.Smith represented Illinois, which had its own classificationat variance with the "Bureau." H. H. Krusekopf emergedas soil survey leader for Missouri at about the same time asJ. O. Veatch appeared in Michigan. These men were amongthe more prominent members.

By 1930, the complexion of the Association had changedmarkedly. Bushnell of Purdue complained that the Society,then called the American Soil Survey Association, was mis-named, for only 2 of 20-odd papers dealt with mapping. H.H. Bennett was emphasizing the erosion problem. EmilTruog of Wisconsin, M. F. Morgan of Connecticut, Rich-ard Bradfield of Missouri, and others were discussing soilchemistry and physics. Sterling Hendricks presented apaper on X-ray studies of soil colloids, a forerunner to claymineralogy. In the event that anyone thinks engineering in-terpretations to be new, note that L. D. Baver discussed theAtterberg "consistency constants," one paper dealt withsoils and pipe corrosion, and another was about soils androads.

By 1935, soil conservation had become a major move-ment. The Soil Conservation Service in the U.S. Depart-ment of Agriculture succeeded the short-lived Soil ErosionService of the U.S. Department of the Interior in that year,with H. H. Bennett as chief. At the December 1935 meetingof the American Soil Survey Association (2), 12 papers andreports dealt with land use and 10 with conservation anderosion control out of 53 in the program. This meeting, heldjointly with the Soils Section of the American Society ofAgronomy, produced a decision to merge the two bodies asthe Soil Science Society of America. This was the formalorigin of our Division V (S-5), corresponding to Com-

252 SOIL SCI. SOC. AM. J . , VOL. 41, 1977

mission V of the International Society of Soil Science. Thisdecision was not without controversy. There had been somesentiment for absorbing the Association in the AmericanSociety of Agronomy. There was stronger conviction withinthe membership that soil science is a discipline in its ownright and should not isolate itself from horticulture and otherusers of soil by formal affiliation with field crops. Thatviewpoint was supported strongly by the group that becameDivision V. The bylaws specified, therefore, that the SoilScience Society should operate as an independent body.Some of you will remember that a similar controversy ex-isted when the American Society of Agronomy wasreorganized and Division V became Division S-5.

CONTROVERSY OVER SOIL SURVEYS1935 was also the year of Marbut's untimely death.

Charles E. Kellogg, who had risen rapidly in soils affairs byway of Michigan, Wisconsin, and North Dakota, succeededDr. Marbut as Chief of the Federal Soil Survey Division. Inthis author's judgement, Dr. Kellogg more than any singleman of his or later generations is responsible for the exis-tence of the Soil Survey as we know it and for the correla-tive states of morphology, genesis, and classification.

Some of us remember vividly the bitter struggle betweenthe Soil Conservation Service and the Division of Soil Sur-vey of the (then) Bureau of Plant Industry, Soils, and Agri-cultural Engineering.

The SCS led by H. H. Bennett and E. A. Norton andbacked by the enormous resources of that agency developedwhat was called a "utilitarian survey." The survey wasbased on mapping combinations of single soil attributes,such as depth, slope, and texture. The attributes selectedwere conceived as controlling factors for soil use and con-servation. They were treated as independent variables inmapping, and the resulting thousands of combinations wereinterpreted in the original land use capability classes.

The Soil Survey Division of the Bureau of Plant In-dustry, Soils, and Agricultural Engineering was led by Dr.Kellogg and his staff. The Soil Survey Division positionwas anchored in the Tennessee Valley and in most stateswith strong soil survey committments in other regions. Thisgroup insisted on a soil survey based on mapping units con-ceived as natural genetic soil entities which could be in-terpreted for a broad range of uses.

The controversy raged through the late 1930's and the1940's. Only Dr. Kellogg's intellectual toughness and therespect he commanded allowed the survey to maintain theprinciples we accept as fundamental to our science. Thecontroversy was finally resolved most ingeniously in 1952by consolidating soil survey activities of the two agencies inthe Soil Conservation Service, but under Dr. Kellogg'sleadership. The philosophy of the "Bureau" prevailed, butfiscal support of the federal soil survey depended on satis-fying the applied functions of the Soil Conservation Ser-vice. This marked a turning point from which the NationalCooperative Soil Survey as we know it today has emerged.It is likely that without the solution which was found, wewould not have the new soil taxonomy (14), nor the inten-sive studies of soil morphology and genesis which made itpossible. It is likely too that the enormous progress in soilsurvey interpretations could not have been made.

CHANGING CONCEPTSAt this point in time, three philosophies of soil had

emerged. The one, sponsored by early soil conservationistsjust described, conceived soil as an assemblage of proper-ties associated as independent variables. In effect, its propo-nents of the 1940's denied genetic theory, or ignored it aspurely academic. There are elements of this approach incurrent numerical taxonomy, though that may be applied inthe context of genetic theory. Another, illustrated by Dr.Jenny's important book, Factors of Soil Formation (7)focused on genetic theory in terms of functional rela-tionships subject to quantitative proof. Its perspective real-istically conceived soil as a continuum of sets of propertieswith few discontinuities marking limits of discrete kinds ofsoil. It was not primarily geographically oriented and didnot, by itself, lead easily to definition of mapable soilbodies. A third, represented by the soil survey, started withdefinition of relatively homogeneous genetic soil bodies thatcould be mapped at large scale. It proceeded to genetic ex-planations through geographic correlation of sets of soilproperties with the soil-forming factors under which theywere found. In the early years, those explanations wereexpressed qualitatively in terms of gross soil-forming pro-cesses, such as the "podzolization" and "laterization" ofthe 1938 Yearbook of Agriculture (3). Over the years, thisthird approach has dominated in America, largely becauseof the impetus and resources of the soil survey. Increas-ingly, however, the soil survey has moved from qualitativeto quantitaive procedures, and functional relationships havebecome important tools.

The Soil Survey Manual (13) marked a major contribu-tion toward quantitative morphology. Soil Taxonomy (14)has forced the soil survey into quantitative procedures. Itsclasses are defined quantitatively in terms of limits. Its de-velopment required assembling the existing quantitativedata from the field and laboratory and unprecedented addi-tional work of both to fill the gaps. Its application hasrequired a remarkable transformation from qualitative toquantitative data gathering by the field force.

Rarely do recent papers of this division explain soilproperties in terms of the gross soil-forming processes usedso commonly in the past. Many discuss individual reactionsor processes that explain observed phenomena. Our ideashave shifted from concepts of general processes unique foreach environment to soil genesis as an aggregate of manyindividual reactions and physical changes, each of whichmay be a potential contributor in many environments. Thedata we gather increasingly provide numbers that can beused to define functional relationships.

We have come to appreciate more fully the role of geo-morphic processes. With this has come realization that soilsin absolute equilibrium with the current environment areprobably rare. As a corrollary, we postulate continuing slowaging involving successive stages we can recognize as dif-ferent kinds of soil. We are much more conscious that thesets of properties we see in many, if not most, soils of theUnited States may be temporary and conditioned by eventsof the Pleistocene. Changing environments and the stabilityof geomorphic surfaces loom much larger in our geneticmodel.

Soil Taxonomy is, without doubt, the most important

CLINE: HIGHLIGHTS IN SOIL GENESIS, MORPHOLOGY, AND CLASSIFICATION 253

single contribution of the past 25 years. Dr. Guy Smith, its Soil Taxonomy will continue to change in detail, espe-principal architect, must be ranked among the outstanding daily for the tropics. It is so new, however, that it willindividuals of that period. Because the criteria are quantita- probably be another 20 or 30 years before changing con-tively defined soil attributes, it is commonly said that the cepts will require a major reconstruction. As Soil Tax-bases of classification are these attributes and not theories of onomy is applied in old landscapes, especially in the trop-genesis. That is true for those who apply the system. But ics, it will certainly erode concepts of the zonality of somethose who made the system deliberately grouped together in soil-forming processes still further. At the lowest level oftaxa those soils which were conceived to have had common the system, we will have to acknowledge the differences be-genesis. Then they looked for criteria to distinguish among tween taxonomic soil series and mapping units that bear thethe groups. In that sense, therefore, concepts of genesis are same name and will probably have to rectify the confusionas fundamental to Soil Taxonomy as to Marbut's system or this causes. It is conceivable that soil families could becometo that of the 1938 Yearbook of Agriculture. the lowest category of taxonomy, but some ingenious per-

Within that framework, however, Soil Taxonomy repre- son may find a better solution.sents a major change in the concept of a class. That change There is probably greater opportunity in the near futurehas far-reaching consequences. Prior to Soil Taxonomy, the for major changes in soil interpretations than in most otherfocus of attention was on a central concept, or typifying in- aspects of our work. New computer techniques for retriev-dividual, of each "taxon." The limits of the taxon were not ing interpretive information in both language and car-defined and were perceived in terms of similarity ordissimi- tographic form will, in a very few years, revolutionize thelarity to the central concept. Attention was focused on the service which can be provided. At the same time, we shouldinternal composition of each taxon. Soil mappers had much recognize that most of our interpretations are analytical andlatitude in deciding limits of similarity, and measures of that many are qualitative. Many of them merely rate limita-"inclusions" in mapping units were correspondingly sub- tions or potentials for use. We have an opportunity, work-ject to personal judgements. Soil Taxonomy defines class ing with scientists of other disciplines, to tell land userslimits in quantitative terms. This focuses attention on the what must be done, if anything, to change the soil to suitboundaries of taxa. What is inside those boundaries be- their purposes. This is an outstanding opportunity. We mustcomes less distinct. That definition of taxa has forced quan- beware of the pitfalls of computer technology, however,titative studies by field workers, as noted above. It has also The fact that we have interpretations of available datacut the landscape in the field along sharply defined lines locked into our data banks could obstruct innovations thatwhich may not coincide with mappable boundaries. As a would make them obsolete.consequence, "inclusions" are more than 50% of many Although there are great opportunities for progess, onemapping units identified as taxa, though the precision of can also see potential problems in some trends. It appearsmapping has not changed or has increased. Taxajuncts may that there is a tendency for some in the most responsibleoccupy a high proportion of mapping units. We have been positions of both state and federal cooperators in the Soilcompelled to acknowledge that soil taxa and mapping units Survey to lose contact with the field. That is understand-identified by the same name are two distinctly different able, for they are beset by endless problems. But it isthings. serious, for we lose the practicality of decisions based on

the real world when armchair pedolegists determine policy.THF FITTITRF (")ne a'so nears complaints from some field workers that

their standing in their agencies is deteriorating. We needWhat of the future? This individual's crystal ball is cer- them as respected colleagues both in their agencies and in

tainly as cloudy as another's, but a few things seem clear. this society. Some of us can remember when the field forceThe new Soil Survey Manual will bring some important ad- was treated like unskilled labor and many performed ac-justments in soil morphology such as horizon designations cordingly as a result. Conversely, one detects a tendency forand consistence terms. One would expect that the texture workers in the field to accept Soil Taxonomy as "the gospeltriangle will be reconciled with particle-size classes of soil according to St. Guy." In part, this may be a consequencefamilies eventually, but that will take study. It would appear of growing authoritarianism, which often goes with big-that we will continue to extend our morphological work to ness. Whatever the cause, this was far from the intent. Soilgreater depths as soil interpretations demand it. Taxonomy was constructed deliberately to reveal its incon-

In soil genesis, we now have masses of data which will sistencies with the facts of nature and to force changes whensoon be easily available through modern data processing theory does not fit the facts.techniques. It would be surprising if these were not ex- This presentation is filled with evidence of personal bi-ploited increasingly to develop quantitative functional rela- ases. Individuals may agree or disagree with its conclusionstionships. That could create new ideas and expose errors in according to their own perspectives, but one may hope thatcurrent concepts, which could change our thinking dras- it will stimulate reflection and, perhaps, ideas that will con-tically. One may expect consciousness of geomorphic his- tribute to knowledge of the subject of Division S-5 (V).tory to continue to expose time relationships. We may beable to reconstruct the environments of the past, when soilsof the present were developing, and estimate their effects.This could change our ideas. One can predict that we willcome to recognize that many more of our soils than we haverealized contain vertical discontinuities of material, somebig and some small.

254 SOIL sci. soc. AM. J., VOL. 41, 1977