Properties and Classification of Kitsap Soils in Northwestern Washington1

H. F. SHOVIC, B. E. FRAZIER, AND R. A. GiLKESON2

ABSTRACTThe Kitsap series is widely distributed in the Puget Sound Low-

lands. It has developed in glaciolacustrine sediments under the in-fluence of cool, wet winters and warm, dry summers. This series isa benchmark soil and it has been classified as prime land for agri-culture and forestry in Washington. Fourteen sites, representing thegeographic range of this series, were characterized in the field. Fourpedons were selected from characterization in the laboratory. A typ-ical pedon which represents the central concept of the Kitsap seriesis described. The range of chemical and physical properties, genesis,and classification are discussed.

Kitsap soils occupy intermediate terraces in major stream drainagesand along some bluffs facing Puget Sound. The two most importantsoil-forming processes are the accumulation of organic matter andthe transformations and redistribution of iron. These processes yielda thick, but relatively light-colored epipedon, concretions, mottles,and durable aggregates. The clay fraction is dominantly vermiculitewith extensive Al-hydroxy interlayers. Laboratory and field charac-terization data support the placement of these soils in Aquic Xero-chrepts. However, at the family level the data indicate that these soilsas they are currently mapped fit (i) fine, mixed, mesic, (ii) fine-silty,mixed, mesic, and (iii) fine, vermiculitic, mesic.

Additional Index Words: Glaciolacustrine sediments, Aquic Xero-chrepts, concretions.

Shovic, H. F., B. E. Frazier, and R. A. Gilkeson. 1982. Classifi-cation and variability of Kitsap soils in northwestern Washington.Soil Sci. Soc. Am. J. 46:1253-1258.

THE KITSAP series was first identified in KitsapCounty and became an established series when

correlation was completed for the Kitsap County Soilsurvey in 1938. Since then, phases have been mappedin 11 other surveys, four of which have been com-pleted in the last 10 years. The series is a benchmarksoil and has been classified as prime land for agri-culture and forestry in Washington. It is also a prob-lem soil for development as it is subject to mass move-ment and has restricted internal drainage. The objectiveof the study was to locate, characterize, and classifypedons that would represent the central concept ofthe Kitsap series, over its geographic range. Its gen-esis and classification are discussed in terms of mor-phological, physical, chemical, and mineralogicalproperties.

SOIL-FORMING FACTORSThe lowland surrounding Puget Sound is part of a tectonic

trough, bordered by the Olympic Mountains on the westand the Cascade Range on the east. The area has beenrepeatedly glaciated during the Pleistocene. The most recentadvance was the Vashon Stade of the Fraser glaciationwhich retreated about 13,000 years ago (Easterbrook, 1969).Proglacial lakes were common during the last retreat, and

1 Scientific Paper no. 5831. College of Agriculture Research Cen-ter, Washington State University, Pullman, WA 99164. Project no.0900. Received 26 Jan. 1981. Approved 6 July 1982.2 Soil Scientist, U.S. Forest Service, Gallatin NF, Bozeman,Mont., and former Graduate Student, Washington State University,Assistant Professor and Professor, Dep. of Agronomy and Soils,Washington State University, Pullman, WA 99164.

remnants of the associated sediment bodies are now in manyparts of the lowlands.

Kitsap soils occur on four distinct landforms: (i) well-defined lacustrine terraces in old proglacial stream valleysthat incised the upland till plain, (ii) lake beds in lineardepressions between long drumlinoid hills on the upland tillplain, (iii) lacustrine terraces bordering the arms of PugetSound, and (iv) extensive, slightly eroded lake beds bor-dering the southern end of Puget Sound. Lacustrine ter-races in proglacial stream ways are the most common land-form. Geographically associated soils are (i) the Alderwoodand Harstine soils on glacial till plains and drumlinoid hills,(ii) the Everett and Indianola soils on outwash portions ofterraces and upland plains, (iii) the Bellingham soils thatoccupy depressions in the lacustrine material, and (iv) thePastik soils, which are near the northern-most range of theKitsap series, and which have volcanic ash over lacustrinematerials.

The vegetation has changed from lodgepole pine (Pinuscontorta Dougl. ex Loud.) which colonized the fresh driftto Douglas-fir (Pseudotsuga menziesii Mirb. Franco) andwestern hemlock (Tsuga heterophylla Raf. Sarg.) (Huesser,1965). The present forest on Kitsap sites is primarily Doug-las-fir and red alder (Alnus rubra Bong.) with a dense un-derstory of bracken (Pteridium aquilinum L. Kuhn) andswordfern (Polystichum munitum Kaul F. Presl), salal(Gaultheria shallon Pursh), big sting nettle (Urtica dioicaL.), and Oregon-grape (Berberis aquilifolium Pursh). Mostof the old growth forest has been clearcut and burned inthe past and the long-lived, serai Douglas-fir is now domi-nant (Franklin and Dyrness, 1973). Roughly 40% of theKitsap soils are currently in pasture, cropland, or urbanuse.

The climate in the Puget Lowlands has gradually warmedfrom a cool, moist, post-glacial climate to the milder, marinetype at present. Summers are warm and dry, and wintersare cool and wet. Average annual precipitation ranges from80 to 140 cm where the Kitsap soils are found. The averageannual minimum and maximum temperatures are about 4and 16°C, respectively. The frost-free season is 160 to 200 d.

METHODSTwo pedons were selected from each survey area, one

located as near as possible to the type location for the surveyand the other from a randomly selected delineation of a mapunit having a different slope phase. Descriptions of themapping unit and soils were recorded for each site. Figure1 depicts both the distribution of the Kitsap soils and thesample sites. Each pedon was described using NationalCooperative Soil Survey procedures and terms (USDA,1981).

Four sites (1, 4, 5, 7, Fig. 1) were selected for chemicaland physical characterization. These represent the range inprecipitation and geographic limits. All were found on ter-races of low relief and slope (<5%) in permanent pastureat the time of sampling.

Primary particle-size classes and degree of aggregationwere determined by the pipet and by the Day hydrometermethods, respectively (Black, 1965). Samples for primaryparticle-size determination were cleaned and dispersed with30% H2O2, Na-dithionite-citrate-bicarbonate (DCB), andNa hexametaphosphate with agitation (Kittrick and Hope,1963; Black, 1965). The samples for determination of pe-dality were treated with H2O2 and Na-.Pa hexametaphos-phate only.

1253

1254 SOIL SCI. SOC. AM. J . , VOL. 46, 1982

/ UUHI ,' •yt : i-•'-—T ISLANdgs_. A14.__._..J-_-A

I \(c< /*•>< A ?-.. i \vx : _x*SMr&**~,«. tp-v> \CLALL'AM-V'J

\i——.—_jJEFFERSON

0lympiaflHURS%NX /

; Kitsap Sails NSea... °, , 2° | 4,01""

Maximum Extant of VashonStade of Prater Glaciation

Fig. 1—Distribution of the Kitsap soils and the location of samplesites.

Cation exchange capacity (CEC) and exchangeable cat-ions were determined for the <2-mm soil by NH4OAc atpH 7.0 (USDA, 1972). Cation exchange capacity was alsodetermined for four samples at pH 6.0, and using 80% meth-anol-20% water.

Reaction (pH) was determined using saturated pastes thathad been equilibrated for about 1 h. Organic carbon wasdetermined using H2SO4-dichromate oxidation. Iron and Alwere extracted using the DCB method (Kittrick and Hope,1963) and Na pyrophosphate at pH 8.2 (USDA, 1972).

Clay mineralogy was estimated from x-ray diffractionpatterns of Mg-glycerol (Mg-gly) and K-saturated samplesheated to 25, 300, and 550°C. Minerals in the very fine sandfraction were identified with a petrographic microscope.About 300 grains were counted for each sample.

RESULTS AND DISCUSSIONTypical Pedon

The pedon is located on a lacustrine terrace withina proglacial drainageway. This drainageway emptiesnorthward into the Puyallup River Valley, and is 3 kmin width at the outlet narrowing to 0.4 km south ofthe site. Kettle-like depressions containing ponds andbogs are common in this area. The pedon is withina 300-ha delineation of the map unit Kitsap silt loam,2 to 8% slopes (Zulauf, 1979: sheet 29). Slope is 2%at the pedon, elevation is 110 m, and estimated pre-cipitation is 100 cm. Vegetation is common pasturegrasses. The profile was dry through the Bw horizon,but very moist in the BC. Textures were estimated.No field evidence of thixotropic properties was found.

Table 1—Average physical and chemical properties for the four Kitsap pedons by horizons.

Depth to lowerHorizon

AptMeanRange

BwMeanRange

BCMeanRange

MeanRange

Ap_MeanRange

BwMeanRange

BCMeanRange

CMeanRange

Thickness

—————— cm

(22)2317-30

(21)1913-21

(45)4220-52

„-

pH

(5.7)5.85.6-6.2

(5.9)5.85.4-6.2

(6.0)5.85.5-6.3

(6.5)6.76.5-6.9

boundary

(22)§2317-30

(43)4236-51

(88)84156-102

„-

Organiccarbon

%

(4.2)3.92.8-4.6

(1.3)1.31.0-1.8

(0.4)0.40.3-0.6

(0.2)0.30.2-0.3

>2-mmconcretions

(19.3)18.65.3-40.2

(24.6)11.64.0-24.6

(0) 0.10.0- 0.5

00

CEC

————— meq/I

(26.7)27.621.9-31.5

(16.9)20.216.9-23.7

(18.3)24.018.3-29.1

(15.5)21.315.5-28.0

Sand

(12.5(15.46.3-26.6

( 7.8) 8.25.4-12.4

( 2.1) 1.60.3- 3.0

(19.2) 5.40.1-19.2

Exch.bases

LOOg —————

( 5.9) 6.65.9- 8.1

( 3.4) 6.43.4- 8.9

(13.3)17.913.3-23.8

(11.6)17.711.6-24.4

Primary

Silt

—————————— °/i

(60.7)49.343.4-60.7

(62.8)53.242.7-62.8

(73.8)56.128.4-73.8

(65.8)65.457.2-74.3

Basesaturation

DCB ironf

Clay^ ——————————————————

(26.9)35.225.1-48.8

(29.4)38.629.4-50.1

(24.1)42.424.1-70.7

(15.0)29.315.0-42.7

Ca

Whole soil

(0.7)1.10.7-1.6

(0.9)1.00.7-1.3

(0.8)0.90.6-1.3

(0.7)0.60.3-0.9

Mg

Concretions

(1.5)1.61.1-2.1

(1.2)1.71.0-2.4

(0) 0.40.0-1.4

00

Na K

% —————————————— meq/100 g ——————————————

(22.1)24.420.3-29.5

(20.1)31.120.1-44.5

(72.7)73.160.8-81.7

(74.8)78.566.3-87.3

(5.0)5.34.4-6.5

(2.5)4.12.5-5.2

(6.1)9.16.1-12

(6.3)8.96.3-12

(0.7)1.00.2-1.7

(0.8)2.00.7-3.3

(6.8)8.25.4-12

(4.9)8.24.9-12

(0.1)0.10.1-0.2

(0.1)0.10.1-0.2

(0.2)0.30.2-0.5

(0.2)0.30.2-0.3

(0.2)0.30.2-0.4

(0.1)0.20.1-0.3

(0.2)0.40.2-0.5

(0.2)0.30.2-0.5

t DCB = Dithionite-citrate-bicarbonate extraction. The weighted average of the < 2-mm soil and concretions was used for the whole soil percentage.t For Site 5, the values for the Ap and Al horizons were averaged.§ Values in parentheses are for Site 4 (the typical pedon).1 For Site 1, values for the B32 horizon were used, rather than the B31.

SHOVIC ET AL.: PROPERTIES AND CLASSIFICATION OF KITSAP SOILS IN NORTHWESTERN WASHINGTON 1255

Table 2—Mineralogical composition of very fine sand for the four Bw horizons determined by petrographic microscope.

Horizon Quartz FeldsparOpaque

Fe MicaWeathered

micaVolcanic

ashPhytolithscharcoal

Weatheredminerals Other

Site 1 BwSite 4 BwSite 5 BwSite? Bw

Average

25222021

32263424

2442

0213

————— 70 ————

95013

2795

81444

20202422

2046

22 29 22

HorizonAp

Depth,cm0-22

DescriptionDark brown (10YR 3/3) silt loam, brown (10YR5/3) dry; strong coarse granular; soft, very fri-able, slightly sticky, slightly plastic; many veryfine roots; many very fine tubular and manyvery fine interstitial pores; 5% rounded gravel;many 2- to 5-mm concretions; pH 5.7; abruptsmooth boundary.

Bw 22-43 Dark brown (10YR 4/3) silt loam, very palebrown (10YR 7/3) dry; moderate coarse gran-ular; soft, friable, slightly sticky, slightly plastic;many very fine roots; common, very fine tu-bular and many very fine interstitial pores; 5%rounded gravel; many 3- to 8-mm concretions;few krotovinas; few 5-cm pockets of 7.5YR5/6 material, which contain many 3- to 8-mmconcretions; pH 5.9; abrupt irregular boundary.

BC 43-88 Light olive brown (2.5Y 5/4) Silt loam, paleyellow (5Y 7/3) dry; weak, coarse, angularblocky, parting to weak, fine, angular blpcky;slightly hard, friable, slightly sticky, slightlyplastic; few very fine roots; common very finetubular and common coarse tubular pores; 5%rounded gravel; very many continuous promi-nent brown (10YR 5/4) mottles intermingledwith light brownish gray (2.5Y 6/2); pH 6.0;abrupt irregular boundary.

C 88-100 Light olive brown (2.5Y 5/4) silt loam, paleyellow (5Y 7/3) dry; structureless laminations;slightly hard, firm, slightly sticky, slightly plas-tic; few fine, tubular pores; pH 6.5.

Forested Kitsap soils differ little from the abovedescription except in the surface horizons. This isexpected since the area of Kitsap soils was foresteduntil this century. Forested sites have litter layers andthinner A horizons and a pH in the solum which isabout 1 unit lower than nonforested sites, probablya result of vegetation. The thickness ranges for thesehorizons are 10 to 30 cm for A, 19 to 58 cm for Bw,and 35 to 153 for BC. Mixing of the B horizons istypical in these soils because of tree blowdown.

Parent Material and MineralogyKitsap soils have developed in lacustrine sediments

that are normally stratified with occasional lenses ofsand or gravel. Silt and clay make up 86 to 98% ofthe <2-mm fraction (Table 1).

The mineralogy of the very fine sand from the Bwhorizons of the four pedons is similar, with about 55%relatively unweathered minerals, largely quartz andfeldspar with minor amounts of mica and volcanic ash(Table 2). Weathering may have altered the less-resistant minerals, leaving about 7% weathered micaand 24% other weathered minerals. Charcoal (7%)provides evidence of disturbance by burning.

Mineralogy of the <0.002-mm fraction was deter-mined for the Ap and BC horizons of four pedons(Fig. 2). Three samples are dominated by vermiculiteor vermiculite interlayered with hydroxy-Al (Table 3).

Magnesium-glycerol saturation expands vermiculiteinterlayer spacing to 14A, oand K saturation shouldcollapse the spacing to 10A. This occurs in the BChorizons of Sites 1, 4, and 7. The A horizon samplesrequired heating to at least 300°C to collapse the layersto about 10A, indicating hydroxy interlayers werepresent that degraded with heat (Barnhisel, 1977). Thepeaks for A horizons are broad because different de-grees of interlayering produce various combinationsof spacings. The BC of Site 5 has a pattern which istypical of chlorite dominance.

Similar mineralogy is displayed by the geographi-cally associated Alderwood soils which are developedin ablation till over basal till (Brackett, 1966). Ver-miculite is the dominant clay mineral with lesseramounts of chlorite, illite, and kaolinite present. Theyalso contain about 56% quartz and feldspar in the veryfine sand fraction which is similar to the Kitsap pedons(Table 2).

Iron TransformationsIn the Kitsap soils, the three main morphological

features that result from transformations of iron areconcretions, durable peds, and mottling. Formationof concretions is thought to be related to Fe solutionduring saturation and an accretion process around anucleus (such as a primary particle) during a subsequentdrying period. Conditions important to this processinclude impeded internal drainage and distinct wettingand drying cycles. Waterlogging causes mottling orgleying, and good aeration causes oxidation, both ofthese processes resulting in fewer concretions. Max-imum concentrations of concretions are normallyfound above the depth of maximum development ofmottles. These phenomena have been noted by others(Schwertmann and Fanning, 1976; Gallaher et al.,1973; Clark and Brydon, 1963; Wheeling, 1936).

The Kitsap soils are concretionary in the Ap andBw horizons, whereas the BC and C horizons aremottled or gleyed. Mottling is occasionally intermixedwith the concretions, but if so, the concretions aresoft and poorly formed. The Ap and Bw horizons aredepleted of growth moisture during the summer months,whereas the BC and C commonly remain moist. Thesoil is saturated yearly during winter and spring. Ironis believed to be an important cementing agent sinceconcretions contain an average of 1.5 times the DCBFe in whole soil (Table 1).

Durable peds are probably formed by processessimilar to those involved with concretion formation,but with smaller concentrations of Fe. A comparisonwas made of four horizons from pedon 4 (PierceCounty) to determine differences in pedality and lackof pedality (primary) particle-size distribution (Table

1256 SOIL SCI. SOC. AM. J., VOL. 46, 1982

I = Mg-gly 25°C2= K25°C3= K300°C4= K550°C

BC HORIZONS4,7 7 93 14 A ^5 4,7 7 93 14 ,

I = Mg-gly 25°C2 = K25°C3= K300-C ,

Fig. 2—X-ray diffractograms of <2-/um fractions of A and BC horizons from sites 1, 4, 5, and 7.

4). These data indicate that the A and Bw horizonscontain significant amounts of small durable peds inaddition to the concretions noted in field descriptions.The BC and C horizons lack both concretions anddurable peds. In these soils the Ap and Bw have adistinct wet-dry seasonal cycle, whereas the C ho-rizon remains near saturation during the dry season.The entire profile is saturated during the wet season.Periodic wetting and drying accompanied by reductionand oxidation processes apparently promote formationof concretions and peds. Because of this pedality,

Table 3—Clay mineralogy of the A and BC horizonsof the four pedons.

Relative amount of minerals t

Site

SitelThurston CountyType siteSite 4Pierce CountyType siteSitesKing CountyType siteSite?Jefferson CountySecondary site

Dominant

AlHy Verm

AlHyVerm

AlHy Verm (Ap)Chlorite(BC)

AlHy Verm

Moderate

Verm

Verm

RinterV-CChlorite (Ap)VermVerm

Trace

IlliteChloriteRinter V-CIlliteChlorite

Illite

IlliteChloriteKaolin! teHornblende

results from particle-size analysis will depend on theefficiency of dispersion, particularly for A and Bwhorizons.

In most pedons, prominent mottling is restricted tothe BC and C horizons. The most common featuresare yellowish brown mottles which follow root chan-nels, cracks, large pores, and stratification planes.These indicate areas of dominant oxidation. The soilmatrix is grayish; in nine of 14 pedons it has a chromaof 2 or less, and in four others, it is 3. Iron and otherelements are probably in a reduced state in the soilmatrix, indicating that there are significant periods ofwaterlogging with reducing conditions. This periodicsaturation of the profile is due to a combination ofhigh water table, rainfall, low permeability of the com-pact C horizon, topographic position, and lessenedevapotranspiration during the cloudy winter months.

Table 4—Comparison of particle-size distributions for fourhorizons of Pedon 4 (Pierce County) with and without

durable peds.

With durable pedst Peds disintegrated!

Horizon Sand Silt Clay Sand Silt Clay

t AlHy Verm = aluminum hydroxy interlayered vermiculite. Rinter V-C= randomly interstratified vermiculite and chlorite. Verm = vermicu-lite. Relative amounts of clay minerals were estimated by relativeheights and areas of peaks. Amounts apply to both horizons exceptwhere one horizon designation appears.

ApBwBCC

1716719

74617370

————— "/9132011

'a ——— ——

138219

60637466

27292415

t Day hydrometer method (organic matter was removed with H2O2 treat-ment).

J Pipet method (in addition to H,O, treatment, sequioxides were removedwith Na-dithionite treatment).

SHOVIC ET AL.: PROPERTIES AND CLASSIFICATION OF KITSAP SOILS IN NORTHWESTERN WASHINGTON 1257

Other ProcessesThe degree of clay formation in the solum is un-

certain. The dominance of vermiculite (Table 3) couldbe due to weathering from chlorite or mica, but itcould also be geologic in origin (Douglas, 1977). Theprominant Al-hydroxy interlayers could also be aweathering product. The resistance of the interlayersof the A horizon clays to collapse with K saturationsuggest that they are well formed and tenacious. TheKitsap soils have a moderately active weathering en-vironment with seasonal high precipitation and mildtemperatures, pH 6.0 is average, and they have annualwet-dry cycles. These conditions are similar to thosesuggested by Barnhisel (1977) as being favorable forinterlayer formation. It seems probable that hydroxyinterlayers could form in the solum and that they arebetter formed in the A than BC horizons.

Exchange PropertiesAlthough the high CEC values are reasonable, con-

sidering the high organic matter and clay content(Table 1), the base saturation is much lower than ex-pected for a soil having a pH of 5.8 (an average of24.4% for A horizons).3 The figures could be explainedby a large pH-dependent increase in exchange capac-ity from pH 5.8 to 7.0; however, measurements ofCEC at pH 7.0 show no change.

Another possible cause is error related to salt re-tention by amorphous materials (Bohn et al., 1979).This was investigated by changing the wash solventfrom the standard 95% ethanol-5% water to 80%methanol-20% water. Since NH4OAc is much moresoluble in the latter than in ethanol, salts should beretained to a lesser degree with a given volume ofwash (Smith et al., 1966). A decrease of 5 meq wasnoted in the A horizon with no change in the others.This decrease is not sufficient to explain the low basesaturation. A larger decrease may be obtained if the

3 Reaction is lower in forested pedons, implying a base saturationwhich is lower.

volume of wash is increased or centrifuging is sub-stituted for leaching on the wash step.

ClassificationAt present, the Kitsap series is classified as a fine-

silty, mixed, mesic Aquic Xerochrepts (USDA, 1980).The diagnostic horizons are the ochric epipedon andcambic horizon.

The four pedons that were characterized meet therequirements for the umbric epipedon except for color(Table 5). Munsell values and chromas commonlyrange above the moist and dry limits for the Bw ho-rizons and in the Ap horizon of Pedon 7. Therefore,the epipedon is ochric.

The BC horizons of most of the sample pedons meetthe requirements of a cambic horizon as they arewithin 50 cm of the mineral surface (with the exceptionof Pedon 5, which is at 51 cm), and they are dominatedby low chroma colors (Table 6).

Table 6—Classification of the 14 pedons.

Ochric epipedonDepth of Depth to

Depth of Depth Cambic mottles ofPe- AporAl ofBw BC chroma 2don horizon horizon horizon or less Classification familyi

Particle-size

IT2t3t4t5t67T8T9

iotlit12t1516f

1720232230142322141023132222

3836504351393658531928203933

cm ———90

1308788

102555687

153§8966358582

3836234351

>853622

>153102820

>8541

Aquic Xerochrept FineAquic XerochreptAquic XerochreptAquic Xerochrept Fine siltyAquic Xerochrept FineTypic XerochreptAquic Xerochrept Fine siltyAquic XerochreptTypic XerochreptAquic XerochreptAquic XerochreptAquic XerochreptTypic XerochreptAquic Xerochrept

t Pedons used for typical pedon selection and for taxon definition.j Known only for those where clay content was determined.§ Lower boundary of the BC horizon was indistinct.

Table 5—Color value and chroma, dry consistence, and structure of A, B, and C horizons for representative pedons.

Horizon

Pedon 1ApBwBC

CPedon 4

ApBwBC

CPedon 5

ApBwBCC

Pedon 7ApBwBCC

Organiccarbon, %

4.021.000.38

0.22

4.181.320.36

0.19

5.051.760.320.29

2.761.060.610.29

Munsell colorValue/Chroma

Moist

3/25/46/4

6/3

3/34/35/4

5/3

3/35/45/45/3

3/34/34/35/2

Dry

5/37/47/2

8/3

5/37/37/3

7/3

5/36/47/37/3

5.5/37/27/37/2

Dry consistence

Slightly hardSlightly hardHard

Very hard

SoftSoftSlightly hard

Slightly hard

Slightly hardSlightly hardHardHard

Slightly hardSlightly hardHardHard

Structure

Strong, very coarse, granular (moist)Weak, very coarse, granular (moist)Moderate, medium, angular blocky parting

to moderate, fine, platy (moist)Structureless laminated

Strong, coarse, granular (dry)Moderate, coarse, granular (dry)Weak, coarse, angular blocky parting to

weak, fine, angular blocky (moist)Structureless laminated

Strong, coarse, granular (dry)Moderate, medium subangular blocky (dry)Weak, medium, angular blocky (dry)Structureless laminated

Strong, medium granular (dry)Moderate, medium, angular blocky (dry)Weak, very coarse, angular blocky (dry)Structureless laminated

1258 SOIL SCI. SOC. AM. J . , VOL. 46, 1982

The moisture regime for these soils has not beendetermined, but because they are normally dry forlong periods during the summer and early fall, it isassumed to be xeric. Therefore, the classification ofthe 14 pedons at the great group level is Xerochrepts(Table 6).

For the great group Xerochrepts, requirements forthe aquic subgroup are (i) low chroma (=£2) mottlingwithin 75 cm of the soil surface, and (ii) saturationof the soil in the mottled horizons at some time ofyear, usually in the winter or spring (Soil Survey Staff,1975). Since 11 of 14 pedons meet both requirementsthe suggested classification to subgroup level is AquicXerochrepts (Table 6).

The classification at the family level is in doubt.Climatic data clearly indicate a mesic temperatureregime, but the particle size as determined vary acrossthe fine, fine-silty borderline so that it is difficult tosay which is representative. The mean clay percentagein the control section (25 to 100 cm) is within the finefamily (Table 1); however, the range of particle-sizedistribution indicates that some pedons (1 and 5) arefine while others (2 and 4) are fine-silty. Field esti-mates of texture favor fine-silty because sand and silt-sized aggregates of fine material produce tactile prop-erties related to a coarser texture. The soil landscapeprovides no clues in separating these soils, as all ofthese pedons are on similar landforms and slopes.

Mineralogy of the clay fraction is a family char-acteristic for fine families. The dominant clay mineralin the control sections of three pedons is vermiculitewith Al-hydroxy interlayers. Pedon 5 has chlorite inthe BC horizon. Based on data for these four pedons,the vermiculitic family would be the most represen-tative. Thus there are three possibilities: fine-silty,mixed, mesic; fine, mixed, mesic; and fine, vermic-ulitic mesic. It is unlikely that this can be resolveduntil more is known about the variability of the clayfraction of the polypedons representing the Kitsapseries.

SUMMARYThe Kitsap soils are formed on glaciolacustrine sed-

iments under forest. The climate is cool, wet wintersand warm, dry summers. The effects.of waterloggingduring the winter dominate the lower part of the profile(BC and C) causing mottling, gleying, and poor aer-ation and root growth in the C horizon. The upperpart of profile (A and Bw) shows the effects of irontransformations to form concretions and durable pedswhich, along with organic matter, provide good tilthin a fine-textured soil. The durability of aggregates offine material interfere with dispersion for particle-sizeanalysis.

The Kitsap soils are mesic, Aquic Xerochrepts with

a control section that is borderline between fine andfine-silty and clay mineralogy that varies from ver-miculitic to mixed.

ACKNOWLEDGMENTSThe authors wish to acknowledge the assistance of the

staff of the Agronomy and Soils Department, WashingtonState University, in this research. The authors are alsograteful to the personnel at the University of Idaho SoilCharacterization Laboratory for their help in the chemicalanalysis.