Reference soil Kenya 66: Vertisol

KE066

Vertisols occur dominantly in level landscapes under climates with a pronounced dry season. Vast areas are found in Australia, India, northeastern Africa (Sudan, Ethiopia), southern Latin America and the USA.

Characteristics

Soils having a vertic horizon (a clayey subsurface horizon with polished and grooved ped surfaces ("slickensides") or wedge-shaped or parallelepiped structural aggregates) within 100 cm from the soil surface. They have 30 percent or more clay in all horizons to a depth of 100 cm or more, or to a contrasting layer (lithic or paralithic contact, petrocalcic, petroduric or petrogypsic horizons, sedimentary discontinuity, etc.) between 50 and 100 cm, after the upper 20 cm have been mixed. In addition, Vertisols exhibit wide cracks, which open and close periodically.

Distribution of Vertisols (rough estimation supplied by soilgrids)

Reference soil KE066: Vertisols

The profile is an intergrade towards a vertic cambisol. No tuff in situ appears! Acacia drenpanolobium is a typical Vertisol shrub. Slides: 10,242 - 10,247.

Classification

WRB 2006

WRB 1998

calcic horizon- Vertisol (Pellic)

Pelli-calcic horizon- Vertisol

15-64 cm	vertic horizon
-	secondary carbonates

FAO-UNESCO-ISRIC 1988

FAO-UNESCO-ISRIC 1974

Orthi-Calcic Vertisol gilgai

Pellic Vertisol

0-15 cm	ochric A horizon
15-64 cm	cambic B horizon
-	slickensides
-	soft powdery lime

0-15 cm	ochric A horizon
15-64 cm	cambic B horizon
-	gilgai microrelief
-	slickensides

Other classification

USDA-NRCS (1999)	Leptic Haplustert
USDA-SCS (1975)	Leptic Pellustert ustic clayey isothermic

More images

Physical characteristics

Particle size distribution

Depth (cm)	Gravel % v/v	very coarse sand % w/w	coarse sand % w/w	medium sand % w/w	fine sand % w/w	very fine sand % w/w	Total sand % w/w	coarse silt % w/w	fine silt % w/w	Total silt % w/w	Clay % w/w
0-15	0	12.1	11.7	6.3	6.6	2.3	39	7.3	15.3	22.6	38.5
15-50	5	10.4	11.6	5.8	5.7	2.9	36.4	6.4	14.1	20.5	43.0
50-65	45	16.6	12.7	8.6	7.0	2.5	47.4	4.5	13.4	17.9	34.8

Water retention characteristics

Depth (cm)	Bulk density kg/dm³	Spec. Surf. Area m²/g	COLE cm/cm	Water disp. clay %	Clay % w/w
0-15	-	-	-	-	38.5
15-50	-	-	-	24.5	43.0
50-65	-	-	-	20.0	34.8

Chemical data

Depth (cm)	pH H2O	pHKCl	EC 1: 2.5 dS/m	CaCO3 % w/w	C % w/w	N %	C / N	Exch. Acid cmol(c)/kg	Exch. Al cmol(c)/kg	Ca cmol(c)/kg	Mg cmol(c)/kg	K cmol(c)/kg	Na cmol(c)/kg	Sum Cations cmol(c)/kg
0-15	6.8	5.4	0.12	2.0	1.23	0.13	9	-	-	34.0	6.3	0.4	0.8	41.5
15-50	7.8	6.2	0.13	2.0	0.70	0.07	10	-	-	39.2	4.9	0.2	1.7	46
50-65	8.7	7.2	0.25	7.6	0.70	0.06	12	-	-	53.6	3.5	0.2	2.4	59.7

Depth (cm)	Base sat. %	CEC soil cmol(c)/kg	CEC clay cmol(c)/kg	CEC org cmol(c)/kg	ECEC cmol(c)/kg	Al sat. %	ESP %
0-15	97	42.7	104	4.3	-	-	2
15-50	98	46.8	107	2.5	-	-	4
50-65	125	47.7	143	2.5	-	-	5

Clay mineralogy

Depth (cm)	Chlorite	Feldspar	Gibbsite	Goethite	Halloysite	Hematite	Kaolinite	Mica / illite	Mixed-layer	Quartz	Smec	Vermiculite
0-15	-	weak	-	-	-	-	weak	-	-	weak	very strong	-
50-65	-	weak	-	-	-	-	weak	-	-	weak	very strong	-

Profile description

Ah 0-15 cm	very dark grey (2.5Y 3/0, moist) very dark grey (2.5Y 3/0, dry)slightly gravelly clay,strong medium and coarse angular blocky,very hard firm sticky plastic,many very fine pores and few fine pores,many very fine and few fine roots,very few medium gravel weathered quartz,moderately calcareous (2-10%),clear smooth boundary to,
Ai 15-48 cm	very dark grey (2.5Y 3/0, moist) very dark grey (2.5Y 3/0, dry)slightly gravelly clay,strong very coarse prismatic,very hard extremely firm sticky plastic,broken slickensides,many very fine pores and few fine pores,many very fine and few fine roots,few medium gravel weathered quartz,moderately calcareous (2-10%),diffuse smooth boundary to,
ACi 48-64 cm	very dark grey (2.5Y 3/0, moist) very dark grey (2.5Y 3/0, dry)gravelly clay,strong medium and coarse prismatic and strong coarse and very coarse prismatic,very hard extremely firm sticky plastic,continuous slickensides,many very fine pores and few fine pores,many very fine and few fine roots,moderately calcareous (2-10%),clear irregular boundary to,
2RC 64-76 cm	very dark grey (10YR 3/1, moist) (10YR4.5/ 2, dry)silty clay loam,massive,slightly sticky plastic,continuous slickensides,dominant weathered gneiss fragments,strongly calcareous (10-25%),

Depth1	76cm
Kind 1 (parent material) ; Parker (eds), 1984	tuff
Kind 2 (parent material) (second entry); Parker (eds), 1984	gneiss
Mode of accumulation or deposition of parent material	fluvial
Mode of accumulation or deposition of parent material (second entry)	residual material
Remarks on Parent Materials	transported tuff on gneiss
Soil Depth	76cm
Texture of parent material	clayey
Texture of parent material (second entry)	mixed
Weathering Resistance	poor
Weathering Resistance (second entry)	moderate
General characterization of the status of weathering of solid rock	highly
General characterization of the status of weathering of solid rock (second entry)	partially or moderately

Occurrence of soil aggradation (McDonald et al., 1984)	present
Soil erosion type	sheet
Slope stability	stable

Land use or vegetation in the immediate vicinity of the site	semi-natural grassland, grazed
Remarks on Land Use / Vegetation	VEGETATION: Shrubbed grassland; Acacia drenpanolobium is the typical shrub
Major vegetation type; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	medium tall grassland

Altitude	1750m
Physiographic Unit	valley in gently undul. plain
Physiographic position of the site	lower slope
Regional landform; McDonald, R.C., Isbell, R.F. et all, 1984; Australian soil and land survey Field Handbook, Inkata Press, Melbourne.	plain
Slope	3%
Form of the slope surrounding the site	concave
Topography; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	undulating

Drainage class ; FAO (2006) - Guidelines for soil description	imperfect
Dry From - To	0-80cm
Flooding frequency (FAO, 1986)	irregular
Nature of flood water	fresh
Kind of ground water table (USDA, 1979)	no groundwater table observed
Estimated permeability (class) of least permeable part of the profile	slow
Estimated run off (class)	rapid

Evidence of alkali ; Soil Survey Manual USDA, 1951	slightly alkaline
Average size of stone	1
Surface cracking	large cracks (width more than 1 cm, or depth more than 50 cm)
Slaking of aggregates by tillage, rainfall or frost (USDA/SCS, 1979)	surface slaked; sorted sand/silt, some clay films
Microrelief Height: variation in height	15
Micro relief type: small-scale differences in relief in the direct vicinity of the site (FAO, 1986)	gilgai
Microrelief pattern	none
Rock outcrop class (FAO (2006) - Guidelines for soil description)	none
Evidence of salt; Soil Survey Manual USDA, 1951	non-saline
Shape of stones (on average)	(sub-)rounded
Surface stoniness class (FAO (2006) - Guidelines for soil description)	very stony

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Reference soil Kenya 66: Vertisol

Characteristics

Reference soil KE066: Vertisols

Classification