Reference soil South Africa 09: Vertisol

ZA009

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 ZA009: Vertisols

BRIEF CHARACTERIZATION OF THE SOIL: A very dark brown to black clayey profile showing pronounced intersecting slickensides in the lower part. The soil is non calcareous throughout. MICRO RELIEF: irregular polygonal pattern (diameter 30-40cm) of cracks ADDITIONAL NOTES ON PROFILE DESCRIPTION: AC - few continuous slickensides in the upper part, continuous slickensides increasing in number with depth and intersecting.

Classification

WRB 2006

Grumic- Vertisol (Eutric)

35-120 cm

vertic horizon

35-120 cm

vertic horizon

FAO-UNESCO-ISRIC 1988

FAO-UNESCO-ISRIC 1974

Chromi-Eutric Vertisol

Chromic Vertisol

0-35 cm	ochric A horizon
35-120 cm	cambic B horizon
-	slickensides
-	vertic

0-35 cm	ochric A horizon
35-120 cm	cambic B horizon
-	slickensides
-	vertic

Local classification:	Arcadia Form

Other classification

USDA-SCS (1975)

Chromustert ustic

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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
0-20	-	0.5	2.9	5.7	9.5	5.6	24.2	8.6	10.0	18.6	57.2
20-40	-	0.2	1.4	3.3	7.4	5.8	18.1	8.6	10.9	19.5	62.3
40-60	-	0.2	1.4	3.8	7.7	5.3	18.4	9.5	12.1	21.6	60.0
60-80	-	0.1	0.4	1.5	4.1	3.9	10	10.5	13.1	23.6	66.5
80-100	-	0.3	0.4	1.1	2.6	3.3	7.7	9.9	10.8	20.7	71.7
100-110	-	0.3	0.4	1.1	3.3	3.4	8.5	11.0	16.3	27.3	64.0

Water retention characteristics

Depth (cm)	Bulk density kg/dm³	Spec. Surf. Area m²/g	COLE cm/cm	Water disp. clay %	Clay % w/w
0-20	-	-	-	-	57.2
20-40	-	-	-	-	62.3
40-60	-	-	-	-	60.0
60-80	-	-	-	-	66.5
80-100	-	-	-	-	71.7
100-110	-	-	-	-	64.0

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
0-20	6.8	5.3	0.11	0	1.61	0.14	12	-	-	18.5	19.7	0.3	0.8	39.3
20-40	7.1	5.5	0.12	0	1.31	0.11	12	-	-	24.8	20.9	0.2	1.2	47.1
40-60	7.4	5.9	0.14	0	1.16	0.11	11	-	-	18.7	23.2	0.2	1.7	43.8
60-80	7.6	6.2	0.26	0	1.40	0.10	14	-	-	22.3	24.6	0.3	2.2	49.4
80-100	7.8	6.3	0.27	0	1.11	0.10	11	-	-	22.5	24.4	0.6	2.7	50.2
100-110	8.1	6.6	0.35	0	1.29	0.09	14	-	-	22.2	29.0	0.3	3.1	54.6

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 %
0-20	87	45.2	79	5.6	-	-	2
20-40	95	49.4	79	4.6	-	-	2
40-60	78	56.4	94	4.1	-	-	3
60-80	89	55.5	83	4.9	-	-	4
80-100	88	57.0	79	3.9	-	-	5
100-110	99	55.3	86	4.5	-	-	6

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
0-20	-	-	-	-	-	3.7	0.2	-	-	-	-
20-40	-	-	-	-	-	3.8	0.2	-	-	-	-
40-60	-	-	-	-	-	3.6	0.2	-	-	-	-
60-80	-	-	-	-	-	3.3	0.2	-	-	-	-
80-100	-	-	-	-	-	3.4	0.2	-	-	-	-
100-110	-	-	-	-	-	3.4	0.2	-	-	-	-

Elemental composition of the clay

Depth (cm)	SiO2 % w/w	Al2O3 % w/w	Fe2O3 % w/w	CaO % w/w	MgO % w/w	K2O % w/w	Na2O % w/w	TiO2 % w/w
0-20	46.2	24.1	16.0	0.16	1.29	0.20	-	0.82
20-40	46.6	24.5	16.0	0.16	1.30	0.21	-	0.82
40-60	47.5	24.4	15.0	0.15	1.25	0.24	-	0.84
60-80	47.8	24.2	14.2	0.14	1.24	0.27	-	0.82
80-100	48.3	24.1	14.1	0.15	1.28	0.27	-	0.82
100-110	49.1	24.2	14.4	0.17	1.36	0.26	-	0.84

Depth (cm)	MnO2 % w/w	P2O5 % w/w	Ign.Loss clay % w/w	Total Clay % w/w	SiO2/Al2O3 mol/mol	SiO2/Fe2O3 mol/mol	SiO2 / R mol/mol	Al2O3/Fe2O3 mol/mol
0-20	0.18	0.12	11.2	100.27	3.3	7.7	2.3	2.4
20-40	0.19	0.13	11.1	101.01	3.2	7.7	2.3	2.4
40-60	0.22	0.11	11.1	100.81	3.3	8.4	2.4	2.5
60-80	0.15	0.09	11.2	100.2	3.4	8.9	2.4	2.7
80-100	0.19	0.09	11.0	100.3	3.4	9.1	2.5	2.7
100-110	0.19	0.08	11.1	101.6	3.4	9.1	2.5	2.6

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
0-20	17.1	1.92	11.9	0.42	2.06	-	55.3	1.66
20-40	17.2	1.82	11.7	0.36	1.81	-	54.4	1.45
40-60	16.7	1.48	11.5	0.37	1.50	-	56.0	1.59
60-80	17.9	1.11	12.1	0.33	1.39	-	54.4	1.48
80-100	18.1	1.05	12.2	0.32	1.53	-	54.6	1.48
100-110	17.7	1.05	12.2	0.31	1.63	-	55.2	1.50

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
0-20	2.3	10.0	0.24	0.04	5.5	12.4	3.8
20-40	2.3	10.4	0.25	0.03	5.4	12.4	3.7
40-60	2.3	9.8	0.28	0.03	5.7	12.9	4
60-80	2.3	10.9	0.25	0.03	5.2	12.0	3.6
80-100	2.3	10.9	0.25	0.02	5.1	11.9	3.6
100-110	2.3	10.5	0.28	0.02	5.3	12	3.7

Clay mineralogy

Depth (cm)	Chlorite	Feldspar	Gibbsite	Goethite	Halloysite	Hematite	Kaolinite	Mica / illite	Mixed-layer	Quartz	Smec	Vermiculite
0-20	-	-	-	-	-	-	weak to medium	-	very weak to weak	very weak to weak	strong	-
20-40	-	-	-	-	-	-	weak to medium	-	very weak to weak	very weak to weak	strong	-
40-60	-	-	-	-	-	-	weak to medium	-	very weak to weak	very weak to weak	strong	-
60-80	-	-	-	-	-	-	weak to medium	-	very weak to weak	very weak to weak	strong	-
80-100	-	-	-	-	-	-	weak to medium	-	very weak to weak	very weak to weak	very strong	-
100-110	-	-	-	-	-	-	weak to medium	-	very weak to weak	very weak to weak	very strong	-

Profile description

Ah1 0-15 cm	very dark brown (7.5YR 2/2, dry) very dark brown (10YR 2/2, moist)clay,strong fine subangular blocky,very hard friable very sticky very plastic,non calcareous,clear smooth boundary to,
Ah2 15-35 cm	very dark brown (7.5YR 2/2, dry) very dark brown (10YR 2/2, moist)clay,moderate fine subangular blocky,very hard friable very sticky very plastic,non calcareous,diffuse smooth boundary to,
Bi 35-120 cm	(10YR 1/1, moist)clay,weak very coarse prismatic parting to moderate fine subangular blocky,very hard friable very sticky very plastic,broken slickensides,non calcareous,

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

Land use or vegetation in the immediate vicinity of the site	shrubland, grazed
Remarks on Land Use / Vegetation	VEGETATION: Thornbush, Acacia spp
Major vegetation type; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	shrub

Altitude	750m
Physiographic Unit	valley slope
Physiographic position of the site	middle slope
Regional landform; McDonald, R.C., Isbell, R.F. et all, 1984; Australian soil and land survey Field Handbook, Inkata Press, Melbourne.	low hill
Slope	11%
Slope Aspect	east
Form of the slope surrounding the site	concave
Topography; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	rolling

Drainage class ; FAO (2006) - Guidelines for soil description	imperfect
Dry From - To	0-30cm
Kind of ground water table (USDA, 1979)	no groundwater table observed
Moist From - To	30-120cm
Estimated permeability (class) of least permeable part of the profile	slow
Estimated run off (class)	medium

Evidence of alkali ; Soil Survey Manual USDA, 1951	non-alkaline
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)	no surface slaking/crusting observed
Microrelief Height: variation in height	20
Micro relief type: small-scale differences in relief in the direct vicinity of the site (FAO, 1986)	hummocks
Rock outcrop class (FAO (2006) - Guidelines for soil description)	none
Evidence of salt; Soil Survey Manual USDA, 1951	non-saline
Surface stoniness class (FAO (2006) - Guidelines for soil description)	none

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Reference soil South Africa 09: Vertisol

Characteristics

Reference soil ZA009: Vertisols

Classification