Vertisols and Vertic Properties of Soils of the Cherokee Prairies of Kansas

Published April 8, 2014

Published March 28, 2014

Pedology Vertisols and Vertic Properties of Soils of the Cherokee Prairies of Kansas

Soils in the Kansas Cherokee Prairies have formed in various parent materi- Paul E. Hartley als and exhibit differences in the degree of expression of vertic properties. Kansas Livestock Association Despite large clay contents, few soils meet the criteria for a Vertisol. In an Environmental Services, Inc. effort to investigate the cause of these differences, pedogenic processes, pri- 1303 Yucca St. Scott City, KS 67871 marily clay illuviation and shrink–swell processes, were evaluated in eight pedons. Relatively high coefficient of linear extensibility (COLE) values were DeAnn R. Presley* found in all soils. The clay mineralogy of four sites was dominated by smec- Michel D. Ransom tite, but only two of those sites classified as Vertisols. In the other four sites, smectite was the most common clay mineral, yet there were several other Ganga M. Hettiarachchi clay minerals present in significant quantities. Disruption of illuvial clay fea- Dep. of Agronomy tures by shrink–swell movement was evident in the thin sections of all soils. Kansas State Univ. Striated b-fabrics dominated except in surface soils that exhibited a small 2004 Throckmorton Plant Sciences Center COLE value and occurred above an argillic horizon. Linear planes lined with Manhattan, KS 66506-5501 stress-oriented clay and representing zones of shear failure were observed, along with argillans that had been distorted and embedded within the matrix Larry T. West by swelling pressure and soil movement. In conclusion, when present, a non- USDA–NRCS expansive silty surface layer acts as a buffer and may limit shrink–swell by National Soil Survey Center (retired) allowing expansive subsoils to dry more slowly. 100 Centennial Mall North Lincoln, NE 68508 Abbreviations: COLE, coefficient of linear extensibility; MLRA, Major Land Resource Area; XRD, X-ray diffraction.

he Cherokee Prairies Major Land Resource Area (MLRA) 112 is an area characterized by gently sloping to rolling, dissected plains situated within Kansas, Missouri, and Oklahoma. In southeastern Kansas, the region is Tbounded on the north by the Kansas River and on the west by the Flint Hills physiographic region. Many of the soils in the Cherokee Prairies are characterized by large clay contents and large shrink–swell potential. Although most soils in this region are not classified as Vertisols, their vertic properties and claypan characteristics cause soil management to be difficult and pose problems for agricultural, -en vironmental, and engineering uses. Collecting more information and improving our understanding of the frequency and circumstances where vertic soils are likely to be present are important steps toward improving soil management techniques. A section of MLRA 112 and the area in which all sampling occurred for this study is referred to as the Osage Cuestas physiographic region of Kansas. The Osage Cuestas are named for the low, rolling escarpments that are somewhat steep on one side and gently sloping on the other. Local relief is typically only 1 to 3 m, and major valleys are generally <25 m below adjacent uplands. The region is underlain with alternating layers of shales and limestones of Pennsylvanian and Mississippian age. The soils reflect this geology, and multiple parent materials are often described. Soils form in residuum overlain by colluvium, local alluvium, and/or alluvium. A

Contribution 13-153-J of the Kansas Agricultural Experiment Station. Soil Sci. Soc. Am. J. 78:556–566 doi:10.2136/sssaj2013.06.0217 Received 5 June 2013. *Corresponding author ([email protected]). © Soil Science Society of America, 5585 Guilford Rd., Madison WI 53711 USA All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher.

Soil Science Society of America Journal thin loess cap is also common on upland areas throughout this ample, although commonly occurring in vertic soils, speckled region. The soils in this study area predominantly have a ther- (asepic), stipple speckled (argillasepic or insepic), mosaic speck- Pedology mic soil temperature regime and a udic soil moisture regime. The led (mosepic), and random striated (omnisepic) were considered region has a humid continental climate with an average annual unrelated b-fabrics by Blokhuis et al. (1988). Void types found in rainfall of 865 to 1145 mm. Most precipitation falls from high- vertic soils are not so different than other soils, although planar intensity, convective thunderstorms from late spring through voids often form at shear planes and tend to dominate the subsoil autumn (NRCS, 2006). The humid climate provides adequate horizons of vertic soils. moisture for the processes of in situ clay mineral formation and The objective of this study was to investigate the macro- and clay translocation. micromorphology as well as the clay mineralogy of selected ver- The genesis of nearly all Vertisols and vertic intergrades is tic soils of the Cherokee Prairies MLRA. In addition, we aimed dependent on two conditions: (i) a large quantity of 2:1 expand- to understand the genesis and pedogenic processes, particularly able clay minerals; and (ii) a seasonal wet–dry cycle that causes clay illuviation and shrinking–swelling and the effect that this the expansion and contraction of the soil material (Soil Survey has on the expression of vertic processes, particularly in this re- Staff, 1999). The spectrum of vertic characteristics and proper- gion where Vertisols are not common. ties is wide. Vertic soils occur in nearly every major climatic zone and under many different vegetation types. Materials and Methods The vast majority of vertic soils are dominated by smectite. Field Description and Sampling The smectitic clays may be inherited from the original rock par- Eight pedons representative of the clayey, vertic soils ent material or may have formed in place as a result of neogenesis common to this region were selected for this study (Fig. 1). or transformations from primary minerals. In general, soil-form- Pedons were sampled in the following Kansas counties: Osage, ing processes that lead to the formation of vertic soils control the Franklin, Woodson, Allen, Wilson, and Neosho. Three pedons formation and stability of smectites in soil. Such minerals are were sampled through the spring and summer of 2009: Site A capable of expanding and contracting with changes in the mois- (Bucyrus 09KS139001); Site B (Woodson 09KS059001); and ture status (Eswaran et al., 1988). The expansion and contraction Site C (Summit 09KS207001). The remaining six pedons were of interlayer spaces as well as interparticle shrinkage between sampled and described by NRCS soil scientists before the begin- stacked clay particles and clay particle aggregates (domains) in ning of this study, including: Site D (Woodson 73KS001003); the microstructure is responsible for the shrink–swell phenom- enon that defines vertic soils. Several other minerals can be present in the clay fraction of vertic soils as well and can be in equal or greater abundance than smectite. For instance, kaolinite, vermiculite, clay mica, and quartz often can significantly contribute to the clay fraction. At the microscopic level, plasma separations, stress cutans, and planar voids are characteristic of Vertisols and vertic intergrades (Blokhuis et al., 1988). Lineated zones of oriented plasma (clay particles) in which clay platelets are stacked face to face form within the microfabrics of vertic soils due to the shear stresses associated with swelling. These elongated zones of oriented plasma are known as plasma separations and represent zones of previ- ous shear failure (Coulombe et al., 1996; Wilding and Tessier, 1988). Porostriated (vosepic), granostriated (skelsepic), parallel striated (masepic), and cross-striated (lattisepic) b-fabrics in- dicate microshear (Wilding and Tessier, 1988). Nettleton and Sleeman (1985) cited many researchers who found that shearing produced parallel-striated b-fabrics within the clay-sized material. Gunal and Ransom (2006a) found that shrink–swell was associated with striated b-fabrics in Bt horizons in central Kansas. Often the striated b-fabrics occurred in the upper part of the argillic horizons with larger COLE values (Gunal and Ransom, 2006a, 2006b). Shearing in both the horizontal and vertical di- rections is believed to produce cross-striated fabric (McCormack and Wilding, 1974). Unrelated plasma separations were not considered characteristic of vertic soils by Blokhuis et al. (1988); Fig. 1. Cherokee Prairies Major Land Resource Area 112 is located however, they are commonly described in these soils. For ex- in Missouri, Kansas, and Oklahoma. Eight sites (labeled A–H) were sampled in Kansas.

www.soils.org/publications/sssaj 557 Site E (Zaar 05KS205002); Site F (Zaar 97KS205001); Site G Particular attention was given to the description of the micro- (Kenoma 05KS133003); and Site H (Parsons 06KS133001). All mass and pedofeatures. pedons were sampled by excavating to a depth of 1 to 2 m with a backhoe. Pedons were described using Schoeneberger et al. Laboratory Characterization (2012). For each horizon, bulk samples were taken for laboratory Three clods per horizon were collected for bulk den- characterization, oriented clods were collected for thin section sity measurements (Soil Survey Staff, 2009, Method 3B1), and preparation, and nonoriented clods were sampled and coated in COLE values were calculated (Soil Survey Staff, 2009, Method saran for bulk density measurement. The slope percentage and 3.5.4) Bulk samples were allowed to air dry and were then position were also described. ground with a wooden rolling pin and passed through a no. 10 sieve with 2-mm square openings. Total C and total N were de- Mineralogy termined using a high-frequency induction furnace (Leco Model Total clay and silt mineralogy were analyzed for select- CNS-2000) following the procedure of Tabatabai and Bremner ed horizons by the methods of Jackson (1975). Forty-gram (1970). The particle size distribution was determined using the samples of the <2-mm air-dried fraction were pretreated with methods of Kilmer and Alexander (1949) and Soil Survey Staff −1 1 mol L NaOAc and 30% H2O2 to remove carbonates and (2009, Method 3A1). organic matter, respectively. The samples were dispersed and passed through a 50-mm sieve (300 mesh), where the sand was Results and Discussion collected. The silt and clay fractions were separated through Field Morphology, Laboratory Data, a series of eight sedimentation cycles, where Stokes’ law was and Soil Classification used to calculate sedimentation times for a 10-cm depth of fall The field morphology of these polygenetic soils reflects the (Jackson, 1975). The clay fraction was flocculated with MgCl2 multiple geologic parent materials present in the Osage Cuesta and quick-frozen in a bath of dry ice and ethanol, then the wa- region of Kansas (Table 1). All sites were on low-relief uplands ter was removed through freeze-drying. The silt fraction was and interfluves. Site A was located on a 4% slope on the back- oven dried to a powder. slope of an interfluve. Site B had 1% slope and was on the shoul- Six clay treatments were prepared for each sample: der of an interfluve. Site C was on a 4% slope on the backslope of Mg–25°C, Mg–ethylene glycol, Mg–glycerol, K–25°C, an interfluve. Site D had a 1% slope and the position was noted K–350°C, and K–550°C. Solutions containing 30 mg of clay for only as “nearly level upland.” Site E had 0.2% slope on a tread of each treatment were pipetted onto a glass slide and allowed to a paleoterrace on a hill. Site F had 1% slope on a footslope. Site dry to provide a parallel-oriented mount. G had 1% slope on the shoulder of a tread of a paleoterrace on an A Phillips XRG-3100 generator and an APD X-ray diffrac- alluvial plain remnant. Site H had 4% slope on the backslope of tometer were used to analyze all samples. The instrument was a sideslope of an upland. equipped with a Theta compensating slit, and a monochromatic Mollic epipedon criteria were met at all but Site H, which X-ray beam was obtained using a graphite monochromator. failed to meet the mollic criterion for depth. Site H also con- The instrument was operated with VisualXRD software (GBC tained an albic E horizon and thick argillic horizon from 28 to Scientific Equipment Pty. Ltd.). 205 cm. For this study, the dominant pedogenic processes of The clay slides were scanned from 2 to 34°2q for the interest were translocation of clay and shrink–swell processes. Mg–25°C treatment and from 2 to 15°2q for the other five treat- Soil movement and mixing associated with shrink–swell tends ments. Silt samples were scanned from 18 to 54°2q using ran- to destroy the evidence of clay illuviation (Nettleton et al., domly oriented powder diffraction specimen holders. Mineral 1969). Clay increases and the formation of argillic horizons peaks were identified by their d-spacing, and the relative abun- in the upper part of the profile are primarily caused by clay dance of each clay mineral was estimated using peak intensities. illuviation, but given the humid climate, clay mineral formation through neogenesis is thought to have contributed to the Micromorphology abundance of clay throughout these soils. Clay films are ob- Thin sections were prepared for each horizon by a com- served in the field in the majority of soils in the region but are mercial laboratory (Texas Petrographics) for Sites A, B, and C. best expressed in soils exhibiting the least shrink–swell poten- For Sites D, F, G, and H, thin sections were prepared for selected tial. This was shown, for instance, in the upper argillic hori- horizons by the National Soil Survey Laboratory. (Oriented zons at Site B (Table 2), which generally expressed little evi- clods for thin section preparation were not available for Site E.) dence of vertic soil movement. The Bt1 horizon was described Thin sections were examined with a petrographic microscope with 70% continuous faint black (10YR 2/1), moist, and very (Model Optiphot-Pol, Nikon) using plane- and cross-polarized dark gray (10YR 3/1), moist, clay films on all faces of peds. light. Photographs were taken using a camera system (Model The reverse is true in that soils exhibiting greater shrink–swell UFX, Nikon) attached to the microscope. Thin sections were potential have less strongly developed clay films or none at all. qualitatively described using the terminology of Stoops (2003). The Vertisols at Sites E and F, for example, were described with no clay films.

558 Soil Science Society of America Journal Therefore, the study pedons can be placed into three major categories of clay illuviation vs. vertic properties. Nonvertic soils with silty surface layers (Sites A, B, D, G, and H) occur on slopes of 1 to 4% and have strongly developed argillic horizons. Silt loam and silty clay loam surface soils overlie large shrink–swell Argiudoll Epiaquert Albaqualf Argiaquoll Argiaquoll Argiaquoll

Endoaquert argillic horizons at all but Sites E and F. Sites A, B, D, G, and H Classification Vertic Argiudoll Vertic have an abrupt textural change at the top of the argillic horizon, with >20% clay increase from the overlying horizon (Table 3). fine, smectitic, thermic Aeric fine, smectitic, thermic fine, smectitic, thermic Typic fine, smectitic, thermic fine, smectitic, thermic Vertic fine, smectitic, thermic fine, smectitic, thermic Vertic fine, smectitic, thermic fine, smectitic, thermic Vertic fine, smectitic, thermic fine, smectitic, thermic Aquertic fine, smectitic, thermic fine, smectitic, thermic Oxyaquic fine, smectitic, thermic Oxyaquic fine, mixed, active, thermic Vertic thermic fine, mixed, active, Slickensides were described at Sites B and G, and all four soils had large COLE values in the argillic horizon; however, evidence of soil movement, cracking, and pedoturbation was least apparent at these sites. In contrast, the second group, hereafter referred to as vertic soils, includes Sites E and F, which had slopes of 0.2 and 1%, respectively. These pedons contained little evidence of clay illu- Parent material Parent clayey alluvium clayey viation. No argillic horizon or abrupt textural changes were ob- weathered from shale weathered from shale weathered from shale from cherty limestone from cherty served, and no clay films were described in the field. Evidence of loess over clayey alluvium clayey loess over loess over alluvium/residuum loess over clayey alluvium over residuum alluvium over clayey soil movement and cracking due to shear stress associated with loess over alluvium over residuum alluvium over loess over loess over alluvium over residuum alluvium over loess over loess over colluvium over residuum colluvium over loess over colluvium over residuum weathered colluvium over weathered from shale and limestone soil volume fluctuations was apparent. Many slickensides were described, and the soils exhibited increased COLE values ranging from 0.113 to 0.182 m m−1. Vertic processes potentially de- – – – – – – 186 179

contact stroyed clay films that might once have been present, or shrink–

Paralithic/lithic Paralithic/lithic swell events over several hundred or possibly several thousand years may have caused the mixing of surface and subsurface horizons, resulting in a uniformly clayey soil.

– The third category is one that is transitional between vertic 81–186 56–117 53–210 84–212 97–132 53–179

Slickensides and nonvertic soils in its properties, and there is only one pedon 38–71, 101–174 (Site C) that falls into this group. Site C is a 4% backslope and appears to express characteristics intermediate between the two major groups of soils. Site C has a well-defined argillic horizon, Redox Redox 46–186 26–200 18–210 28–212 48–318 22–179 17–195 28–205 which is not usually present in a Vertisol. However, many slick-

concentrations ensides were described along with wedge structure. Furthermore, the COLE summed to a depth of 1 m was 11 m m−1, which proves that this soil has a significant shrink–swell potential. Site – – – – – – – Albic 18–28

horizon C is classified as a Typic Epiaquert. Even so, the surface horizon of Site C is silty clay loam in texture, with 35% clay, which contrasts with the other nonvertic soils in that they have lower clay contents – – – – – – 56–212 53–179 Cambic

horizon in the surface. Due to this intermediate surface clay content, and because there are clay films in this soil, it appears to be intermediate between the nonvertic and vertic soils in this study. – – Argillic 46–186 26–200 29–210 20–318 17–128 28–205 horizon Mineralogy Figure 2 displays the clay mineral abundance and X-ray dif- – – – – – – – ———————————————— cm fraction (XRD) patterns for two selected sites that represent one 0–18 Ochric Ochric epipedon Vertisol (Site E) and one vertic subgroup (Site G). Smectite dominated the clay fraction, with abundances in selected horizons of

– Site E ranging from 40 to 60% throughout. The same is true for 0–46 0–84 0–56 0–80 0–53 0–71 0–103 Mollic

epipedon one other Vertisol, Site F. However, Sites B and D were also dominated by smectite. At Sites B, D, E, and F, smectite dominated the clay fraction, with abundances in selected horizons ranging from 40 to 60% throughout. Kaolinite was the next most com- Pedon 09KS139001 09KS059001 09KS207001 73KS001003 05KS205002 97KS205001 05KS133003 06KS133001 mon clay mineral in all horizons (15–30%). Clay mica made up 5 to 15% of the clay, and clay-sized quartz usually accounted for

Site <10%. Minor amounts of feldspars were present in all four soils. Table 1. Characteristics and diagnostic horizons of the pedons examined in this study. and diagnostic horizons of the pedons examined 1. Characteristics Table A B C D E F G H www.soils.org/publications/sssaj 559 Table 2. Field morphology of the pedons examined in this study.

Horizon Dominant Field Fe–Mn Horizon Depth Structure‡ Consistence§ Clay films Slickensides boundary† color texture¶ concentrations cm —————————— % —————————— Site A: Bucyrus 09KS139001 Ap 0–11 AS 10YR 2/1 2mgr fr sicl – – – A 11–28 CS 10YR 2/1 2mgr fr sicl – – – BA 28–46 CW 10YR 3/2 1mpr–2fsbk fr sicl 2 – – Bt1 46–60 CS 10YR 4/3 2mpr–2fsbk fi sic 12 30, discontinuous – Bt2 60–81 CW 10YR 4/2 2mpr–2msbk fi sic 12 25, discontinuous 1, discontinuous Btss1 81–100 CW 10YR 4/2 2mpr–2msbk fi c 9 35, discontinuous 10, discontinuous 2Btss2 100–159 CS 10YR 4/2 2copr–2cosbk fi c 7 30, discontinuous 15, discontinuous 2Btss3 159–186 AW 10YR 6/4 2copr–2msbk fi c 5 40, discontinuous 20, discontinuous 2R 186–200 – – – – – – – – Site B: Woodson 09KS059001 Ap 0–8 AS 10YR 3/2 2fsbk–2fgr fr sicl – – – A 8–26 CS 10YR 3/2 2fpr–2mabk fr sicl – – – Bt1 26–56 GS 10YR 3/1 2mpr–2coabk vfi sic 2 70, continuous – Bt2 56–84 GS 10YR 3/1 2mpr–2msbk fi sic 10 60, continuous 5, discontinuous Btssg 84–117 CS 10YR 5/2 2mpr–2msbk fi sic 10 50, continuous 25, continuous Btg1 117–148 GS 10YR 5/1 2mpr–2msbk fi sic 50 30, continuous – Btg2 148–166 GS 10YR 5/1 1mpr–2msbk fi sic 60 25, continuous – Btg3 166–200 – 10YR 6/1 1mpr–2msbk fi sic 60 20, continuous – Site C: Summit 09KS207001 Ap 0–18 AS 10YR 2/1 1msbk–2fgr vfr sicl – – – A 18–29 CS 10YR 3/1 2msbk–2fgr fr sic 5 – – Bt1 29–53 GS 10YR 3/2 2mpr–2msbk fi c 15 30, continuous – Bt2 53–103 CW 10YR 3/1 2mpr–2mabk fi c 25 10, continuous 25, continuous 2Btss1 103–135 GS 10YR 4/3 2cowg vfi sic 8 40, continuous 20, continuous 2Btss2 135–177 CW 10YR 3/3 2mpr–2msbk vfi sic 3 20, continuous 5, continuous 3Btkss 177–210 – 7.5YR 4/6 3vcowg–3fwg vfi c 3 70, continuous 50, continuous Site D: Woodson 73KS001003 A 0–20 AS 10YR 3/1 1fgr fr sil nd# nd – Bt1 20–32 – 10YR 3/1 2fsbk vfi sic nd nd – Bt2 32–49 GS 10YR 3/1 2fsbk vfi sic nd nd – Bt3 49–80 GS 10YR 3/1 2msbk vfi sic nd nd – Bt4 80–97 DW 5Y 5/1 1msbk vfi sic nd nd – Bt5 97–133 – 10YR 5/1 2fsbk vfi sic nd nd 5, discontinuous Bt6 133–159 GW 10YR 5/1 2fsbk vfi sic nd nd – Bt7 159–188 GW 10YR 5/1 2mpr–2msbk vfi sic nd nd – Bt8 188–228 GW 10YR 5/1 2mpr–2msbk vfi sic nd nd – Bt9 228–318 – 10YR 5/1 1msbk vfi sic nd nd – Site E: Zaar 05KS205002 Ap 0–13 CS 10YR 3/1 2msbk–2mgr fi sicl – – – A 13–28 GW 10YR 3/1 2fpr–1mgr vfi sic – – – BA 28–56 CW 10YR 3/1 2mpr–2cogr vfi sic 1 – 2, pressure faces Bg 56–84 GW 2.5Y 4/3 2mpr–2cosbk vfi sic 7 – 1, pressure faces Bssg1 84–106 GW 2.5Y 3/2 3vcopr–2cosbk vfi sic 5 – 3, continuous Bssg2 106–142 GS 2.5Y 4/1 3vcopr–2vcosbk vfi sic 10 – 5, continuous Bssg3 142–163 CS 2.5Y 4/1 3vcopr–2vcosbk vfi sic 20 – 15, continuous Bssg4 163–212 – 2.5Y 4/1 2vcopr vfi c 35 – 10, continuous

In the upper horizons of both Woodson soils, Sites B and D, as tent of other clay minerals. At Sites A, C, G, and H, smectite still well as in the Ap horizon at Site C, small amounts (<10%) of a made up a significant portion of the clay fraction, and as would hydroxy-interlayered mineral were present. This mineral is prob- be expected, this was especially true in the argillic horizons. At ably a hydroxy-interlayered smectite or vermiculite, as suggested Sites A, C, and H, smectite contents increased to as much as 40% by the broad shoulder on the 10 Å peak of the K–25°C treat- in the argillic horizons. The fluctuations in the smectite content ment that persisted when heated to 350 and 550°C (K–350°C tended to reflect changes in the ratio of fine clay to total clay. and K–550°C treatments) (Fig. 3). When the fine clay/total clay ratio increased in the argillic ho- The soils at Sites A, C, G, and H exhibited mineralogy that rizon, the smectite content increased as well. The mineralogy of was still dominated by smectite; however, there was a higher con- the fine clay fraction was not determined for this study, but many

560 Soil Science Society of America Journal Table 2 (continued). Field morphology of the pedons examined in this study.

Horizon Dominant Field Fe–Mn Horizon Depth Structure‡ Consistence§ Clay films Slickensides boundary† color texture¶ concentrations cm —————————— % —————————— Site F: Zaar 97KS205001 Ap 0–22 CS 10YR 2/1 1mabk–1mgr vfi sic – – – BA 22–53 GW 10YR 2/1 2mpr–1msbk vfi sic 2 – – Bss1 53–86 CW 10YR 3/1 2copr–2msbk vfi sic 2 – 15, continuous Bss2 86–117 CS 10YR 3/1 2copr–1msbk vfi sic – – 25, continuous Bkss 117–147 CW 10YR 3/2 2copr–2msbk vfi sic 6 – 25, continuous Bss 147–179 CS 10YR 3/1 1cosbk–1msbk vfi sic 60 – 35, continuous Cr 179–219 – – – – – – – – Site G: Kenoma 05KS133003 Ap 0–17 CS 10YR 3/2 1msbk–2mgr fr sil 1 – – Bt1 17–38 CS 10YR 3/2 2mpr–2mabk fr sic 3 30, continuous – Bt2 38–71 CW 10YR 3/2 2copr–2cosbk fr sic 8 30, continuous 5, continuous 2Btg1 71–101 CW 10YR 4/4 1copr vfi sic 10 20, continuous – 2Btg2 101–128 CW 10YR 4/2 2mpr–2mabk vfi sic 30 20, continuous 2, continuous 2Bssg1 128–156 CS 10YR 4/2 2copr–2cosbk fi sic 10 40, continuous 2, continuous 2Bssg2 156–174 GS 10YR 4/1 2copr–2cosbk fi sic 10 20, continuous 20, continuous 2BC 174–195 GS 2.5Y 4/1 1msbk fi sic 15 – 1, pressure faces Site H: Parsons 06KS133001 A 0–18 GS 10YR 3/2 2fgr vfr sil – – – E 18–28 AS 10YR 4/2 2fsbk–1mgr fr sil 1 – – 2Btg1 28–55 CS 10YR 4/2 2copr–2msbk vfi sic 7 40, continuous – 2Btg2 55–91 GS 10YR 4/2 2copr–2cosbk vfi sic 22 15, continuous – 2Btyg1 91–115 GS 10YR 4/2 2mpr–2cosbk vfi sic 17 20, continuous – 2Btyg2 115–142 GS 2.5Y 4/2 1mpr–2msbk vfi sic 40 20, continuous – 2Btg3 142–176 CS 2.5Y 4/1 1mpr–2msbk vfi sic 45 20, continuous – 3Btg4 176–205 – 2.5Y 5/1 2cosbk–2mabk vfi sic 40 40, continuous 10, pressure faces † A, abrupt; C, clear; G, gradual; D, diffuse; S, smooth; W, wavy. ‡ 1, weak; 2, moderate; 3, strong; f, fine; m, medium; co, coarse; v, very; gr, granular; sbk, subangular blocky; abk, angular blocky; pr, prismatic; wg, wedge. § fr, friable; fi, firm; v, very. ¶ sil, silt loam; sicl, silty clay loam; sic, silty clay; c, clay. # nd, no data. studies have found that smectites often make up nearly the entire involving the replacement of K by Mg or Ca in alternate inter- fine clay fraction (Gunal and Ransom, 2006a). layer zones (Sawhney, 1989). Kaolinite contents at Sites A, C, G, and H were generally The field morphology and basic laboratory characteriza- greater than in the Woodson (Sites B and D) and Zaar soils (Sites tion data allowed placement of the eight study pedons into three E and F) and ranged from about 25 to 45%. Vermiculite was groups (nonvertic, vertic, and intermediate). Most Vertisols are as- found in all four of the soils that contained lower amounts of sumed to have a large smectite fraction that, along with the climate, smectite (Sites A, C, G, and H). creates shrink and swell cycles. In this study, however, mineralogy At Sites A, C, and G, an interstratified mineral was identi- alone did not explain the presence of vertic properties. The vertic fied in some of the horizons. This mineral was interpreted to be soils, Sites E and F, are indeed dominated throughout by smectite. a regularly interstratified mica–smectite or regularly interstrati- The intermediate Site C has mixed mineralogy. Of the five nonver- fied mica–vermiculite (a distinction between the two was not tic pedons, two have smectitic mineralogy and three have mixed made), having a regularly repeating pattern of interstratified lay- mineralogy. Therefore, mineralogy does not seem to be the driving ers of mica and either smectite or vermiculite. This mineral was factor behind the occurrence of Vertisols in MLRA 112. identified in XRD patterns of the Mg–25°C treatment based on the presence of shoulders and small peaks at about 24 Å (data Micromorphology not shown). Several other researchers have found both regularly Micromorphologic investigations were undertaken pri- and randomly interstratified minerals similar to these (Sawhney, marily to examine the extent of clay illuviation and the effects 1989; Gunal and Ransom, 2006a; Murashkina et al., 2007; of shrink–swell. In all soils, disruption of illuvial clay features by Fanning et al., 1989; Moore and Reynolds, 1997). Murashkina et shrink–swell movement was evident. Striated b-fabrics domi- al. (2007) and Sawhney (1989) termed this mineral hydrobiotite. nated, except in surface horizons overlying argillic horizons with It is thought to form as an alteration product of mica weathering small COLE values (Table 4). Differences among horizons were

www.soils.org/publications/sssaj 561 generally varying amounts of illuviated clay that Table 3. Selected physical and chemical properties of the pedons examined in this study. were preserved either on void and grain surfaces Oven-dry bulk or embedded within the matrix. Illuviated clay was Horizon Depth Texture† Sand Clay FC/TC‡§ COLE§¶ Total C density§ distinguished from stress-oriented clay based on the cm — g kg−1 — kg kg−1 g cm−3 m m−1 g kg−1 sharpness of boundaries and the thickness of the Site A: Bucyrus 09KS139001 normally linear-shaped oriented clay zones. Stress- Ap 0–11 sil 44 266 0.64 1.26 0.049 37.7 oriented clay and illuvial clay that has been deformed A 11–28 sicl 42 307 0.64 1.48 0.036 20.5 by pressure tended to have characteristics of the ma- BA 28–46 sicl 40 356 0.68 1.39 0.05 16.4 Bt1 46–60 sic 42 474 0.77 1.68 0.088 11.8 trix fabric and more diffuse boundaries and often re- Bt2 60–81 sic 35 552 0.8 1.85 0.102 7.8 sembled large linear striations under cross-polarized Btss1 81–100 sic 33 521 0.77 1.83 0.088 3.0 light. Some well-developed clay films were observed 2Btss2 100–159 sic 43 516 0.76 1.88 0.089 0.0 2Btss3 159–186 c 17 674 0.67 1.6 0.118 0.0 in the argillic horizons of these soils; however, they 2R 186–200 – – – – – – – appeared discontinuous in the thin section (Fig. 4). Site B: Woodson 09KS059001 Gunal and Ransom (2006a) reported, in a study of Ap 0–8 sil 20 239 0.68 1.28 0.033 30.2 A 8–26 sil 20 249 0.69 1.49 0.044 17.6 loess-derived soils in Kansas, that illuvial argillans Bt1 26–56 sic 15 470 0.77 2 0.126 12.6 were not observed when the plasmic fabric was lat- Bt2 56–84 sic 13 459 0.75 1.96 0.103 4.9 tisepic or striated. The Gunal and Ransom (2006a) Btssg 84–117 sic 22 451 0.76 1.88 0.103 2.9 report suggests that large voids and ped surfaces do Btg1 117–148 sic 43 459 0.8 1.85 0.082 0.0 Btg2 148–166 sic 52 461 0.83 1.83 0.096 0.0 not persist long enough to accumulate clay particles; Btg3 166–200 sic 47 481 0.82 1.81 0.108 0.0 however, based on the distorted, embedded rem- Site C: Summit 09KS207001 nants of old illuvial features, significant transloca- Ap 0–18 sicl 49 353 0.68 1.33 0.079 49.5 A 18–29 sicl 53 362 0.7 1.54 0.072 26.6 tion and illuviation of clay is apparent. While study- Bt1 29–53 sic 36 544 0.77 1.85 0.131 15.2 ing Vertisol formation in a humid climate, Nordt et Bt2 53–103 c 26 596 0.75 1.82 0.127 6.2 al. (2004) observed argillans in the lower part of the 2Btss1 103–135 c 45 580 0.33 1.89 0.107 6.0 2Btss2 135–177 sic 54 491 0.53 1.82 0.088 3.2 pedon but not in the upper horizons where shrink– 3Btkss 177–210 c 23 621 0.28 1.92 0.107 0.0 swell activity was greatest. They concluded that Site D: Woodson 73KS001003 translocation of clay was occurring, but clay films A 0–20 sil 22 252 0.6 1.42 0.033 24.9 were preserved only in the lower pedon where ped Bt1 20–32 sic 12 461 0.78 1.76 0.103 15 Bt2 32–49 sic 7 563 0.79 1.9 0.138 12.7 and void surfaces were more stable. Other studies of Bt3 49–80 sic 10 525 0.76 1.87 0.099 9.6 soils in humid climates reached similar conclusions Bt4 80–97 sic 30 455 0.76 – – 4.8 (Mermut and Jongerius, 1980; Yeríma et al., 1987; Bt5 97–133 sic 29 459 0.77 1.79 0.075 2 Bt6 133–159 sic 29 478 0.77 1.77 0.087 1.5 Wilding and Drees, 1990). Bt7 159–188 sic 35 491 0.69 – – 1.4 Surface layers at Sites A, B, C, D, and H had no Bt8 188–228 sic 42 462 0.73 1.85 0.097 0.8 evidence of accumulations of oriented clay and were Bt9 228–318 sic 33 506 0.64 – – 0.7 Site E: Zaar 05KS205002 almost entirely dominated by stipple-speckled b- Ap 0–13 sic 17 467 0.72 1.89 0.113 16.5 fabric in the plasma fabric or micromass. Surface ho- A 13–28 sic 13 568 0.65 1.9 0.135 8.1 rizons at these sites exhibited a more open granular BA 28–56 sic 18 561 0.5 1.94 0.143 6.3 or subangular blocky structure, whereas the argillic Bg 56–84 sic 25 531 0.32 1.98 0.141 6.4 Bssg1 84–106 sic 47 488 0.25 1.96 0.144 7.8 horizons in the subsoils were much more dense, with Bssg2 106–142 sic 36 466 0.19 1.95 0.13 5.4 accommodating channels and many linear planes re- Bssg3 142–163 sic 35 484 0.22 1.88 0.122 3.7 sulting from shrinkage and shear slippage (Stoops, Bssg4 163–212 sic 33 506 0.3 1.88 0.125 2.4 Site F: Zaar 97KS205001 2003). The microstructure of the clayey surface ho- Ap 0–22 sic 27 425 0.7 1.77 0.12 23.3 rizons at Site F (one of the Vertisols) resembled that BA 22–53 sic 33 444 0.71 1.81 0.137 18.1 of the subsoils in other pedons with a blocky, dense Bss1 53–86 sic 23 556 0.67 1.85 0.182 12.6 Bss2 86–117 sic 33 542 0.44 1.87 0.164 9.3 appearance and the presence of linear planes. Some Bkss 117–147 sic 63 500 0.38 1.86 0.141 11.1 small zones of weakly developed striated b-fabric Bss 147–179 sic 64 510 0.39 1.83 0.131 were present in the Ap horizon at Site F, but stipple- Cr 179–219 – – – – – – – speckled b-fabric was much more common. Site G: Kenoma 05KS133003 Ap 0–17 sil 62 221 0.62 1.53 0.018 20.5 All subsoils exhibited features that were in- Bt1 17–38 sic 33 533 0.76 1.77 0.117 14.8 terpreted as remnants of older illuvial argillans Bt2 38–71 sic 29 550 0.74 1.85 0.125 13.1 that had been deformed and/or embedded within 2Btg1 71–101 sic 107 435 0.46 1.67 0.051 2.9 2Btg2 101–128 sic 119 442 0.48 1.7 0.051 2.9 the matrix by pressure and shearing (Fig. 5 and 6). 2Bssg1 128–156 sic 127 445 0.47 1.79 0.044 3.3 Similar embedded grain argillans were observed 2Bssg2 156–174 c 111 504 0.46 1.75 0.057 3.3 by Wehmueller (1996), Rabenhorst and Wilding 2BC 174–195 sic 121 434 0.32 1.88 0.062 2.5

562 Soil Science Society of America Journal Table 3 (continued). Selected physical and chemical properties of the pedons (1986), and Ransom and Bidwell (1990). Sites A, B, examined in this study. D, G, and H appeared to show the least deformation Oven-dry bulk Horizon Depth Texture† Sand Clay FC/TC‡§ COLE§¶ Total C of argillans. Some illuvial clay coatings appeared un- density§ disturbed, and many others had been embedded, −1 −1 −3 −1 −1 cm — g kg — kg kg g cm m m g kg but their deformation was not as severe as at Sites Site H: Parsons 06KS133001 A 0–18 sil 46 250 – 1.2 0.029 22.8 C and F. Coatings and infillings of silt were found E 18–28 sil 49 231 – 1.4 0.027 10.1 in channels in several soils, especially in the upper 2Btg1 28–55 sic 28 544 – 1.78 0.105 7.1 argillic horizons of Sites A, B, D, G, and H (Fig. 2Btg2 55–91 sic 24 508 – 1.94 0.112 4.1 7). These silt coatings exhibited no birefringence 2Btyg1 91–115 c 50 558 – 1.83 0.096 3.2 colors, suggesting small clay content. Parallel stri- 2Btyg2 115–142 c 43 616 – 1.81 0.111 3.1 2Btg3 142–176 c 34 651 – 1.82 0.124 2.6 ated, granostriated, and porostriated b-fabrics were 3Btg4 176–205 c 44 600 – 1.87 0.104 2.3 present in all subsoils examined. Gunal and Ransom † sil, silt loam; sicl; silty clay loam; sic, silty clay; c, clay. (2006a, 2006b), Presley et al. (2004), Wehmueller ‡ Fine clay/total clay ratio. (1996), and Glaze (1998) also observed striated b- § Analysis by National Soil Survey Laboratory. fabrics in argillic horizons in Kansas. Monostriated, ¶ Coefficient of linear extensibility. cross-striated, and crescent-striated b-fabrics also were observed. Striated b-fabrics generally were the most strongly expressed in the lower part of the profile or in the zone of maximum slickenside development. Many linear planes were observed of varying size (Fig. 7), which were interpreted as slickenside surfaces or zones of shear failure because of large linear zones of stress-oriented clay present on either side of these planes with monostriated b-fabrics.

Model of Soil Genesis The distortion of illuvial clay features observed in thin section suggests that these claypan soils have developed over a great deal of time and incremental stages of development and deposition. A period of significant clay illuviation to create the clay films was followed by a second period of shrink–swell activity that effectively distorted and embedded the clay films. Later, at some point during soil formation, silty, nonexpansive surface soils with underlying claypans developed due to a variety of possible reasons including deposition of loess on top of clayey alluvium or residuum, translocation of clay downward and/ or laterally in the soil, and/or clay particle destruction through ferrolysis (Ransom and Smeck, 1986). Both of the Vertisols oc-

Fig. 3. X-ray diffraction patterns of the A horizon at Site D after K–25°C, K–350°C, and K–550°C treatments. A broad 10 to 14 Å peak persisted when the sample was heated. This is evidence that Fig. 2. Mineralogy and X-ray diffraction patterns of the total clay the mineral layers were not collapsing and suggests the presence of a fraction for selected pedons following Mg–25°C treatment. hydroxyl-interlayered mineral such as hydroxyl-interlayered smectite or vermiculite. www.soils.org/publications/sssaj 563 nodules; 3 Pedofeatures slickensides; many clay coatings; many clay and Fe–Mn hypocoatings; hypocoatings; and Fe–Mn clay coatings; many clay many slickensides; concentrations embedded argillans; common Fe–Mn many slickensides; many clay coatings; many clay and Fe–Mn hypocoatings; hypocoatings; and Fe–Mn clay coatings; many clay many slickensides; concentrations Fe–Mn embedded argillans; many many slickensides; many clay coatings; many clay and Fe–Mn hypocoatings; hypocoatings; and Fe–Mn clay coatings; many clay many slickensides; concentrations Fe–Mn embedded argillans; many many slickensides; many clay and silt coatings; many clay and Fe–Mn and Fe–Mn clay and silt coatings; many clay many slickensides; concentrations common embedded argillans; few Fe–Mn hypocoatings; slickensides; many clay and silt coatings; many clay and Fe–Mn and Fe–Mn clay and silt coatings; many clay many slickensides; concentrations common embedded argillans; few Fe–Mn hypocoatings; common clay and silt coatings; few Fe–Mn concentrations; concentrations; and silt coatings; few Fe–Mn common clay hypocoatings and Fe–Mn clay common embedded argillans; many organic pigment staining; very few patchy clay and silt coatings clay few patchy organic pigment staining; very organic pigment staining organic pigment staining coatings; organic pigment staining; common f clay few patchy planar voids/slickensides concentrations; Fe–Mn coatings; common Fe–Mn clay few patchy slickensides; planar voids many concentrations; CaCO concentrations; common Fe–Mn slickensides; many planar voids many b-fabric strong cross-parallel striated; strong cross-parallel and porostriated grano- strong cross-parallel striated; strong cross-parallel poro- and granostriated poro- and granostriated; cross- poro- and granostriated; striated in ped interiors parallel cross-parallel striated; poro- cross-parallel and granostriated strong cross-parallel striated; strong cross-parallel poro- and granostriated cross-parallel striated; poro- cross-parallel and granostriated stipple speckled; weak poro- stipple speckled; and granostriated stipple speckled stipple speckled poro- and stipple speckled; granostriated striated; grano- cross-parallel and porostriated striated; grano- cross-parallel and porostriated; stipple speckled Site F: Zaar 97KS205001 Site B: Woodson 09KS059001 Woodson Site B: Porosity many partially accommodating, intersecting, interpedal channels many common accommodating linear planes and microchannels; many partially accommodating, intersecting, interpedal channels many common accommodating linear planes and microchannels; many partially accommodating, intersecting, interpedal channels many accommodating linear planes many and micro-channels; many partially accommodating, intersecting, interpedal channels many accommodating linear planes many and microchannels; many partially accommodating, intersecting, interpedal many many and accommodating microchannels; channels accommodating linear planes pores; many interconnected many partially accommodating, intersecting, interpedal many pores interconnected many and microchannels; channels many partially accommodating, intersecting, interpedal many pores interconnected many and microchannels; channels many inter-connected accommodating channels, micro- accommodating channels, inter-connected many and planes; common smaller pores ( < 0.25mm) channels, accommodating channels, interconnected many and planes; common smaller pores (<0.25 microchannels, mm); few large linear planes partially accommodating channels interconnected many common smaller pores (<0.25 mm); and microchannels; and linear planes; large (2–4-mm-width) vertical many horizontal channels/cracks partially accommodating channels interconnected many common smaller pores (<0.25 mm); and microchannels; linear planes many many partially accommodating, intersecting, interpedal many and micro-channels channels Microstructure moderately separated separated moderately subangular blocky moderately to highlymoderately subangular blocky separated highly separated angular/ highly separated subangular blocky highly separated angular/ highly separated subangular blocky highly separated angular/ highly separated subangular blocky highly separated angular/ highly separated subangular blocky moderately to highlymoderately subangular blocky separated moderately separated separated moderately subangular blocky separated moderately subangular blocky separated moderately subangular blocky not described separated moderately subangular blocky highly separated granular highly separated Depth 166–200 148–166 117–148 84–117 56–84 26–56 8–26 0–22 22–53 53–86 86–117 117–147 0–8 cm Horizon Btg3 Btg2 Btg1 Btssg Bt2 Bt1 A Ap BA Bss1 Bss2 Bkss Ap Table 4. Micromorphology of selected horizons from Site B (nonvertic) and Site F (Vertisol) described following the nomenclature of Stoops (2003). the nomenclature described following and Site F (Vertisol) Site B (nonvertic) of selected horizons from 4. Micromorphology Table

564 Soil Science Society of America Journal curred on lower, flatter landscape positions, which might be ex- The change in texture between the surface silty mantle and pected to have received deposition of soil from upper parts of the clayey subsoil may also be compounded by a difference in the landscape. Site C, the Vertisol with an intermediate surface structure. For example, in eastern Kansas, Eck et al. (2013) ob- clay content as well as preserved clay films, was sampled on a 4% served the structural unit size and orientation in a fine, smectitic, backslope of an upland interfluve. Therefore, landscape position mesic Oxyaquic Vertic Argiudoll of the Grundy series, finding alone also does not aid in the prediction of a Vertisol. units that were oriented horizontally in the surface and vertically in the clayey argillic horizon. After the silty, nonexpansive top- soil is deposited or forms in place, the difference in the clay content, as well as the shape, size, and orientation of the structural units, may act to limit cracking to the surface, and preferential flow through surface cracks is drastically reduced. Thus, differen- tial wetting of the subsoil, needed in the soil mechanics model of Vertisol formation (Wilding, 1982; Wilding and Tessier, 1988), becomes limited due to the buffering effect of the nonexpansive surface soil. Therefore, the shrink–swell potential of the clayey subsoil is not fully expressed because these horizons dry out less rapidly and perhaps less often, which prevents these soils from developing strongly expressed vertic properties and being classified as Vertisols. Vertisols are found where there is no silty cap; argillic horizons are found where the silty cap reduces the inten- Fig. 4. The Btg3 horizon at Site B, showing a laminated illuvial clay feature filling a pore (outlined with a circle). (Cross-polarized light; sity and frequency of wetting and drying in the subsoil, thus pre- frame length is 3325 mm.) serving the clay films. In some soils of the region (i.e., Zaar series, Osage series, two soil series that are similar to the Vertisols present in this study at Sites E and F), shrink–swell and pedoturbation may provide great enough mixing of surface and subsurface horizons to effectively counteract clay translocation. These soils maintain a clayey, large-COLE-value surface soil, as well as deep cracking that extends to the surface.

Conclusions The study pedons belong to two categories of clay illuviation and vertic properties: soils with silty surface layers have strongly developed argillic horizons, and soils that are clayey throughout lack an argillic horizon because of the disruption of illuvial clay by shrinking and swelling. This is a rather empirical statement, and it is quite possible to have soils that are intermediate between Fig. 5. The Bt1 horizon at Site B, with a distorted, embedded argillan separated by a linear shrinkage plane (inside box). Note the lack of the two categories, as evidenced by one site (C) that had a surface illuvial clay coatings on large void surfaces. (Cross-polarized light; texture that was intermediate between the two groups, having frame length is 1330 mm.)

Fig. 6. The Btg3 horizon at Site B, with a distorted, embedded Fig. 7. The Btss1 horizon at Site A, showing silt infilling a channel argillans (many occur in a cluster at the center of the photograph). (a) and stress-related linear planes (b). (Plain-polarized light; frame (Cross-polarized light; frame length is 665 mm.) length is 3325 mm). www.soils.org/publications/sssaj 565 a silty clay loam texture containing 35% clay. Clay mineralogy regrouping phenomena in some Turkish soils. Geoderma 24:159–175. doi:10.1016/0016-7061(80)90041-5 data showed that four sites (B, D, E, and F) are dominated by Moore, D.M., and R.C. Reynolds, Jr. 1997. X-ray diffraction and the identification smectite. Of these four sites, two were classified as Vertisols and and analysis of clay minerals. 2nd ed. Oxford Univ. Press, New York. two are Vertic Argiaquolls. The difference is the presence of an Murashkina, M.A., R.J. Southard, and G.S. Pettygrove. 2007. Silt and fine ? sand fractions dominate K fixation in soils derived from granitic 20-cm mantle of less clayey material on the Vertic Argiaquolls. alluvium of the San Joaquin Valley, California. Geoderma 141:283–293. The remaining four sites investigated in this study contain smec- doi:10.1016/j.geoderma.2007.06.011 tite plus kaolinite, vermiculite, and clay mica. Nettleton, W.D., K.W. Flach, and B.R. Brasher. 1969. Argillic horizons Smectite-dominated mineralogy alone does not explain or without clay skins. Soil Sci. Soc. Am. Proc. 33:121–125. doi:10.2136/sssaj1969.03615995003300010032x influence the amount of soil volume contraction and expansion Nettleton, W.D., and J.R. Sleeman. 1985. Micromorphology of Vertisols. In: or the expression of vertic properties. In all of the non-Vertisols, L.A. Douglas and M.L. Thompson, editors, Soil micromorphology and a large smectite content, in combination with seasonal moisture soil classification. SSSA Spec. Publ. 15. SSSA, Madison, WI. p. 165–196.. Nordt, L.C., L.P. Wilding, W.C. Lynn, and C.C. Crawford. 2004. Vertisol changes, provided enough shrink–swell movement to deform genesis in a humid climate of the coastal plain of Texas, U.S.A. Geoderma clay films and create the striated b-fabrics observed in thin sec- 122:83–102. tion. The distortion of illuvial clay features observed in thin sec- NRCS. 2006. Central Feed Grains and Livestock Region: MLRA 112— Cherokee Prairies. In: Land resource regions and major land resource areas tion suggests that these soils have developed through at least two of the United States, the Caribbean, and the Pacific Basin. Agric. Handbk. different environments: a period of significant clay illuviation 296. U.S. Gov. Print. Office, Washington, DC. p. 355–357. followed by a period of shrink–swell activity. We offer that the Presley, D.R., M.D. Ransom, G.J. Kluitenberg, and P.R. Finnell. 2004. nonexpansive silty surface layer present on the five soils that did Effects of thirty years of irrigation on the genesis and morphology of two semiarid soils in Kansas. Soil Sci. Soc. Am. J. 68:1916–1926. not classify as Vertisols acts as a buffer and limits shrink–swell by doi:10.2136/sssaj2004.1916 allowing expansive subsoils to dry more slowly and have fewer Rabenhorst, M.C., and L.P. Wilding. 1986. Pedogenesis on the Edwards wetting and drying cycles. This conclusion is a tool that practic- Plateau, Texas: II. Formation and occurrence of diagnostic subsurface horizons in a climosequence. Soil Sci. Soc. Am. J. 50:687–692. ing soil scientists can use to predict the presence or absence of a doi:10.2136/sssaj1986.03615995005000030028x Vertisol in the field, particularly in a region where Vertisols are Ransom, M.D., and O.W. Bidwell. 1990. 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