Reference soil Botswana 02: Vertisol

BW002

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

Reference soil BW002: Vertisol

PHYSICAL UNIT: Escarpment with colluvium in the north and floodplain in the south. A very dark grey, very thin clay topsoil overlying a deep homogeneous very dark grey to black clay. Structural elements and cracks are best developed in the top 67 cm. Soil reaction moderately to strongly alkaline.

Classification

WRB 2006

WRB 1998

Pellic-Grumic- Vertisol (Hyposodic)

Grumi-Pellic- Vertisol (Hyposodic)

67-142 cm

vertic horizon

0-33 cm	ochric horizon
67-142 cm	vertic horizon

FAO-UNESCO-ISRIC 1988

FAO-UNESCO-ISRIC 1974

PelliEutric Vertisol

Pellic Vertisol

0-33 cm	ochric A horizon
33-142 cm	cambic B horizon
33-142	slickensides property

0-33 cm	mollic A horizon
33-142 cm	cambic B horizon
33-142	slickensides property

Local classification

Classification information	CPCS (1967): Manale series (deep vertic A)

Other classification

USDA-NRCS (1999	Aridic Haplustert ustic fine montmorillonitic hyperthermic
USDA-SCS (1975)	Aridic Pellustert ustic fine montmorillonitic hyperthermic

Location:

6km SE of Shoshong, S of Serowe

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
0-3	2	-	-	-	-	-	-	9.3	12.5	21.8	51.6
3-33	1	-	-	-	-	-	-	13.0	27.0	40	39.1
33-67	1	-	-	-	-	-	-	7.3	12.9	20.2	55.4
67-96	1	-	-	-	-	-	-	15.5	30.6	46.1	33.0
96-142	1	-	-	-	-	-	16.5	17.7	36.1	53.8	29.7
142-190	69	-	-	-	-	-	-	4.7	12.0	16.7	19.4

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
0-3	8.2	6.5	-	0.9	0.83	0.12	7	-	-	31.8	10.6	2.0	0.2	44.6
3-33	8.7	6.7	0.82	0.5	0.78	0.10	8	-	-	39.1	11.1	0.9	2.0	53.1
33-67	8.8	6.8	0.78	0.6	0.44	-	-	-	-	33.5	11.5	1.0	3.7	49.7
67-96	8.6	6.8	-	0.8	0.74	-	-	-	-	32.5	11.9	0.8	5.4	50.6
96-142	8.5	6.7	-	0.6	0.65	-	-	-	-	35.8	13.3	1.0	5.6	55.7
142-190	8.6	7.0	-	1.1	0.07	-	-	-	-	24.7	9.3	0.6	4.4	39

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 %
0-3	85	52.3	101	2.9	-	-	0
3-33	104	51.3	131	2.7	-	-	4
33-67	85	58.2	105	1.5	-	-	6
67-96	83	60.8	184	2.6	-	-	9
96-142	72	77.6	261	2.3	-	-	7
142-190	86	45.4	234	0.2	-	-	10

Depth (cm)	pH NaF	P Retention %	ODOE	Al o % w/w	Si o % w/w	Fe d % w/w	Al d % w/w	Fe p % w/w	Al p % w/w	C p % w/w	Fe o % w/w
3-33	-	-	-	-	-	1.6	0.2	-	-	-	-
33-67	-	-	-	-	-	1.5	0.2	-	-	-	-

Elemental composition of the soil

Depth (cm)	Al2O3 % w/w	CaO % w/w	Fe2O3 % w/w	K2O % w/w	MgO % w/w	Na2O % w/w	SiO2 % w/w	TiO2 % w/w
0-3	7.5	0.21	1.7	2.98	0.44	-	74.6	0.41
3-33	9.8	0.16	2.5	4.15	0.48	-	67.4	0.34
33-67	10.2	0.24	3.2	3.5	0.91	-	66.2	0.49
67-96	11.3	0.4	3.3	3.12	0.45	-	66.5	0.64
96-142	8.1	0.24	2.4	3.08	0.13	-	70.4	0.40
142-190	12.4	0.30	3.9	2.67	0.74	-	67.4	0.51

Depth (cm)	Al2O3/Fe2O3 mol/mol	LOI % w/w	MnO2 % w/w	P2O5 % w/w	SiO2 / Al2O3 mol/mol	SiO2/Fe2O3 mol/mol	SiO2 / R mol/mol
0-3	6.9	13.1	0.07	0.06	16.9	116.6	14.7
3-33	6.1	15.2	0.10	0.07	11.7	71.7	10
33-67	5	15.1	0.08	0.10	11	55	9.2
67-96	5.4	15.3	0.10	0.04	10	53.6	8.4
96-142	5.3	15.9	0.11	0.03	14.7	78	12.4
142-190	5	14.2	0.06	0.05	9.2	45.9	7.7

Profile description

Ah 0-3 cm	very dark grey (10YR 3/1, moist)clay,strong fine granular,soft friable sticky plastic,slightly calcareous (0-2%),abrupt wavy boundary to,
3-33 cm	very dark grey (10YR 3/1, moist) very dark grey (10YR 3/1, dry)clay loam,moderate medium angular blocky and wedge-shaped angular blocky,very hard firm sticky plastic,few fine pores,common fine and medium roots,slightly calcareous (0-2%),gradual smooth boundary to,
B 33-67 cm	very dark grey (10YR 3/1, moist) very dark grey (10YR 3/1, dry)clay,very weak fine wedge-shaped angular blocky,very hard firm sticky plastic,thin pressure cutans,few very fine and fine roots,few medium hard calcareous nodules,slightly calcareous (0-2%),gradual smooth boundary to,
Bki1 67-96 cm	black (10YR 2/1, moist) black (10YR 2/1, dry)clay loam slightly gravelly,massive,continuous thin slickensides,few very fine roots,very few small calcareous and medium concretions,gradual smooth boundary to,
Bki2 96-142 cm	very dark grey (10YR 3/1, moist) very dark grey (10YR 3/1, dry)silty clay loam slightly gravelly,massive,patchy thin slickensides,few very fine roots,medium calcareous concretions,slightly calcareous (0-2%),gradual smooth boundary to,
142-190 cm	(2.5YR 3/no, moist) red (2.5YR 4/6, dry)sandy loam very gravelly,frequent medium angular hard calcareous concretions,few coarse gravel weathered Calcrete fragments,slightly calcareous (0-2%),abrupt smooth boundary,

General characterization of the status of weathering of solid rock	highly
Remarks on Parent Materials	dolerite
Kind 1 (parent material) ; Parker (eds), 1984	igneous and metamorphic rock
Mode of accumulation or deposition of parent material	residual material
Texture of parent material	loamy
Weathering Resistance	high

Land use or vegetation in the immediate vicinity of the site	semi-natural grassland, grazed
Remarks on Land Use / Vegetation	Savanna, Acacia Mixed Woodland
Major vegetation type; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	semi-deciduous woodland

Regional landform; McDonald, R.C., Isbell, R.F. et all, 1984; Australian soil and land survey Field Handbook, Inkata Press, Melbourne.	pediment
Physiographic Unit	escarpment with colluvium in the north and floodplain in the south
Slope	5%
Form of the slope surrounding the site	concave
Physiographic position of the site	upper slope
Topography; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	undulating
Altitude	1131m

Drainage class ; FAO (2006) - Guidelines for soil description	poor
Moist From - To	0-30cm

Micro relief type: small-scale differences in relief in the direct vicinity of the site (FAO, 1986)	gilgai
Surface stoniness class (FAO (2006) - Guidelines for soil description)	none
Rock outcrop class (FAO (2006) - Guidelines for soil description)	none
Evidence of alkali ; Soil Survey Manual USDA, 1951	moderately alkaline
Evidence of salt; Soil Survey Manual USDA, 1951	non-saline

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Reference soil Botswana 02: Vertisol

Characteristics

Reference soil BW002: Vertisol

Classification