Reference soil Zimbabwe 06: Vertisol

ZW006

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 ZW006: Vertisols

Vertisol

Classification

WRB 2006

Grumic- Vertisol (Calcaric Pellic)

23-132 cm	vertic horizon
-	secondary carbonates

23-132 cm	vertic horizon
-	secondary carbonates

FAO-UNESCO-ISRIC 1988

FAO-UNESCO-ISRIC 1974

Pelli-Calcic Vertisol

Pellic Vertisol

0-23 cm	ochric A horizon
23-132 cm	cambic B horizon
-	slickensides
-	soft powdery lime
-	vertic

0-23 cm	ochric A horizon
23-132 cm	cambic B horizon
-	slickensides
-	vertic

Local classification:	Chisumbanje 3B.2 Series

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
0-23	-	0.8	1.2	1.5	4.4	6.0	13.9	6.4	7.7	14.1	72.0
23-33	-	1.1	1.0	1.2	4.9	4.7	12.9	5.2	6.9	12.1	74.8
33-61	-	0.8	1.1	1.1	3.8	5.1	11.9	4.1	7.7	11.8	76.2
61-87	-	1.0	1.1	1.3	4.8	4.2	12.4	6.0	7.5	13.5	74.0
87-109	-	0.9	1.1	1.2	3.5	5.0	11.7	7.3	7.5	14.8	73.5
109-132	-	0.4	0.5	0.7	3.4	3.4	8.4	7.0	5.2	12.2	79.4
132-175	-	17.1	19.1	14.0	11.3	6.6	68.1	2.3	8.7	11	21.0

Water retention characteristics

Depth (cm)	Bulk density kg/dm³	Spec. Surf. Area m²/g	COLE cm/cm	Water disp. clay %	Clay % w/w
0-23	0.94	-	-	34.4	72.0
23-33	0.92	-	-	37.3	74.8
33-61	1.05	-	-	36.6	76.2
61-87	1.05	-	-	38.4	74.0
87-109	1.13	-	-	40.8	73.5
109-132	1.11	-	-	44.2	79.4
132-175	-	-	-	15.7	21.0

Other physical data

Depth (cm)	Bulk density kg/dm³	pF 0 % v/v	pF 1.0 % v/v	pF 1.5 % v/v	pF 2.0 % v/v	pF 2.3 % v/v	pF 2.7 % v/v	pF 3.4 % v/v	pF 4.2 % v/v
0-23	0.94	-	-	54	50	45	-	28	32
23-33	0.92	-	-	57	55	50	-	32	32
33-61	1.05	-	-	62	58	51	-	39	36
61-87	1.05	-	-	68	66	61	-	40	33
87-109	1.13	-	-	64	62	54	-	41	39
109-132	1.11	-	-	63	61	53	-	42	42

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
0-23	8.1	6.5	0.34	4.4	1.26	0.09	14	-	-	49.4	26.0	2.5	0.1	78
23-33	7.8	6.6	1.00	4.1	1.24	0.11	11	-	-	47.8	30.0	1.6	0.7	80.1
33-61	7.8	6.5	0.90	4.5	1.21	0.10	12	-	-	45.3	30.0	1.8	1.2	78.3
61-87	7.9	6.6	0.52	3.7	1.17	0.08	15	-	-	44.8	33.8	1.9	1.8	82.3
87-109	8.1	6.5	0.46	4.7	1.24	0.09	14	-	-	44.6	33.8	2.0	2.3	82.7
109-132	8.1	6.6	0.53	4.5	1.17	0.08	15	-	-	44.8	34.1	2.0	3.3	84.2
132-175	8.7	6.6	0.30	8.0	0.15	0.01	15	-	-	66.6	33.2	1.0	4.9	105.7

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 %
0-23	95	82.5	115	4.4	-	-	0
23-33	112	71.4	95	4.3	-	-	1
33-61	108	72.4	95	4.2	-	-	2
61-87	115	71.4	96	4.1	-	-	3
87-109	99	83.3	113	4.3	-	-	3
109-132	107	79.0	99	4.1	-	-	4
132-175	126	84.1	400	0.5	-	-	6

Clay mineralogy

Depth (cm)	Chlorite	Feldspar	Gibbsite	Goethite	Halloysite	Hematite	Kaolinite	Mica / illite	Mixed-layer	Quartz	Smec	Vermiculite
0-23	-	-	-	-	-	-	-	-	-	-	strong	-
23-33	-	-	-	-	-	-	very weak	-	-	very weak	very strong	-
33-61	-	-	-	-	-	-	very weak	-	-	very weak	very strong	-
61-87	-	-	-	-	-	-	very weak	-	-	very weak	very strong	-
87-109	-	-	-	-	-	-	-	-	-	very weak	very strong	-
109-132	-	-	-	-	-	-	very weak	-	-	very weak	very strong	-
132-175	-	-	-	-	-	-	very weak	-	-	very weak	very strong	-

Profile description

Ahk 0-23 cm	dark grey (10YR 4/1, moist)clay,strong fine crumb,very friable very sticky very plastic,no cutans,many fine roots,no inclusions,very few fine gravel weathered quartz fragments,no,non calcareous,clear smooth boundary to,
23-33 cm	dark grey (10YR 4/1, moist)clay,moderate very coarse angular blocky,firm very sticky very plastic,broken thin pressure cutans on pedfaces,many fine roots,no inclusions,very few fine gravel weathered quartz fragments,no,non calcareous,gradual smooth boundary to,
Bki1 33-61 cm	very dark grey (10YR 3/1, moist)clay,strong very coarse angular blocky,very hard extremely firm very sticky very plastic,continuous thin slickensides on pedfaces,common fine roots,very few small spherical soft calcareous concretions and few medium spherical soft calcareous concretions,very few fine gravel weathered quartz fragments,no,slightly calcareous (0-2%),diffuse smooth boundary to,
Bki2 61-87 cm	very dark grey (5Y 3/1, moist)clay,strong coarse angular blocky,extremely firm very sticky very plastic,continuous thin slickensides on pedfaces,few medium roots,very few small spherical soft calcareous concretions and few medium spherical soft calcareous concretions,very few fine gravel weathered quartz fragments,no,slightly calcareous (0-2%),diffuse smooth boundary to,
Bki3 87-109 cm	very dark grey (5Y 3/1, moist)clay,moderate coarse angular blocky,extremely firm very sticky very plastic,broken thin slickensides on pedfaces,few fine roots,very few small spherical soft calcareous concretions and few medium spherical soft calcareous concretions,very few fine gravel weathered quartz fragments,no,moderately calcareous (2-10%),diffuse smooth boundary to,
Bkci 109-132 cm	very dark grey (5Y 3/1, moist)clay,MP medium subangular blocky,firm very sticky very plastic,broken thin pressure cutans on pedfaces,few fine roots,few medium spherical hard calcareous concretions and few medium irregular hard calcareous concretions,very few fine gravel weathered quartz fragments and very few fine gravel strongly weathered basalt fragments,no,moderately calcareous (2-10%),abrupt smooth boundary to,
CBk 132-175 cm	light yellowish brown (2.5Y 6/4, moist)very gravelly loamy sand,patchy thin pressure cutans,frequent medium irregular hard calcareous concretions and frequent powdery thread-like calcareous soft segregations,very few fine gravel weathered quartz fragments,no,strongly calcareous (10-25%),

Depth1	132cm
Kind 1 (parent material) ; Parker (eds), 1984	fine-grained basic igneous rock
Mode of accumulation or deposition of parent material	residual material
Remarks on Parent Materials	Karroo basalt
Soil Depth	132cm
Texture of parent material	clayey
Weathering Resistance	high
General characterization of the status of weathering of solid rock	highly

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

Major crops	sorghum
Land improvements ; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	land clearing
Main type of irrigation; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	no irrigation
Land use or vegetation in the immediate vicinity of the site	fallow
Remarks on Land Use / Vegetation	VEGETATION: Mainly Acacia and Dichrostacys cinerea
Rotation scheme ; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	crop with current fallow
Status of vegetation; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	secondary
Major vegetation type; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	deciduous shrub

Altitude	420m
Physiographic Unit	pediplain of Pliocene erosion
Physiographic position of the site	flat
Regional landform; McDonald, R.C., Isbell, R.F. et all, 1984; Australian soil and land survey Field Handbook, Inkata Press, Melbourne.	pediplain
Slope	1%
Form of the slope surrounding the site	straight
Topography; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	flat or almost flat

Drainage class ; FAO (2006) - Guidelines for soil description	moderately well
Kind of ground water table (USDA, 1979)	no groundwater table observed
Moist From - To	0-132cm
Estimated permeability (class) of least permeable part of the profile	slow
Estimated run off (class)	very slow

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)
Microrelief Height: variation in height	10
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
Surface stoniness class (FAO (2006) - Guidelines for soil description)	none

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Reference soil Zimbabwe 06: Vertisol

Characteristics

Reference soil ZW006: Vertisols

Classification