Reference soil Mali 02: Vertisol

ML002

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 ML002: Vertisols

See also unit TI5 of "Mali Land and Water Resources" 1983, PIRT, mapscale 1:500.000 Max.depth watertable without irrigation probably more than 200cm. Wedge shaped structure elements not well visible, tilted shearplanes with slickensides are well visible. Around biopores greyish soil colour. Permeability of the soil is moderately high due to biopores and cracks, which is also reflected by the considerable fluctuation of the watertable. Under cultivation the soil structure is easily destroyed and a compact soil remains settling hard when dry. The soil is classified as chromic Vertisol based on oralinformation of presence of wide open cracks in the dry season; if cracks are not according Vertisol definition the soil will classify as vertic Cambisol. Windspeed is recorded at 10m height. Insolation, relative humidity and windspeed data are taken from Segou meteo station. Monthly precipitation records of a 30 year period are available in the file.

Classification

WRB 2006

WRB 1998

Mazic- Vertisol (Calcaric Hyposodic Chromic)

Chromi-Mazic- Vertisol (Hyposodic)

30-150 cm

vertic horizon

FAO-UNESCO-ISRIC 1988

FAO-UNESCO-ISRIC 1974

Sodi-Eutric Vertisol

Chromic Vertisol sodic

0-30 cm	ochric A horizon
30-150 cm	cambic B horizon
-	sodic
-	vertic

0-30 cm	ochric A horizon
30-150 cm	cambic B horizon
-	slickensides
-	vertic

Local classification:	Moursi

Other classification

USDA-SCS (1975)

Chromustert aridic clayey thermic

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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
0-30	-	1.2	2.8	2.5	2.5	11.2	20.2	12.9	2.3	15.2	64.6
30-60	-	0.9	2.8	2.4	2.7	11.7	20.5	9.7	5.6	15.3	64.2
60-100	-	0.7	2.1	1.7	1.9	11.6	18	13.1	8.5	21.6	60.4
100-150	-	0.8	1.7	1.6	1.6	11.3	17	14.5	5.7	20.2	62.8
150-175	-	1.0	3.1	2.3	2.0	25.5	33.9	14.7	5.2	19.9	46.2
175-250	-	1.9	10.4	7.2	5.6	33.3	58.4	14.1	2.8	16.9	24.7
300-375	-	2.5	8.4	10.1	14.4	18.2	53.6	14.8	5.7	20.5	25.8

Water retention characteristics

Depth (cm)	Bulk density kg/dm³	Spec. Surf. Area m²/g	COLE cm/cm	Water disp. clay %	Clay % w/w
0-30	-	-	-	30.0	64.6
40-45	1.47	-	-	-	-
30-60	-	-	-	32.4	64.2
130-135	1.45	-	-	-	-
60-100	-	-	-	32.9	60.4
100-150	-	-	-	30.9	62.8
150-175	-	-	-	16.1	46.2
175-250	-	-	-	13.2	24.7
300-375	-	-	-	13.9	25.8

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
40-45	1.47	45.9	44.8	43.4	39.5	38.1	34.9	29.8	26.0
130-135	1.45	45.4	44.8	44.0	41.1	40.0	36.8	32.1	27.7

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
0-30	8.1	6.3	0.29	2	0.56	0.06	9	-	-	18.0	4.2	0.2	1.6	24
30-60	8.8	6.8	0.24	2.1	0.18	0.02	9	-	-	20.1	4.5	0.1	2.4	27.1
60-100	8.8	6.8	0.26	1.8	0.18	-	-	-	-	18.4	4.8	0.1	2.7	26
100-150	8.8	6.9	0.26	2.5	0.14	-	-	-	-	21.2	5.3	0.2	2.3	29
150-175	8.9	7.0	0.25	2.6	0.06	-	-	-	-	23.2	4.2	0.1	1.7	29.2
175-250	8.9	7.0	0.20	1.8	0.03	-	-	-	-	15.9	2.6	0.1	1.0	19.6
300-375	8.9	7.1	0.17	1.5	0.0	-	-	-	-	13.8	4.1	0.1	0.7	18.7

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 %
0-30	105	22.8	35	2.0	-	-	7
30-60	128	21.2	33	0.6	-	-	-
60-100	109	23.9	40	0.6	-	-	11
100-150	144	20.2	32	0.5	-	-	11
150-175	190	15.4	33	0.2	-	-	11
175-250	215	9.1	37	0.1	-	-	11
300-375	164	11.4	44	0	-	-	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
0-30	-	-	-	0.2	0.1	1.2	0.2	-	-	-	0.2
30-60	-	-	-	0.2	0.1	1.4	0.2	-	-	-	0.1
60-100	-	-	-	0.2	0.1	1.3	0.2	-	-	-	0.1
100-150	-	-	-	0.1	0.0	0.9	0.1	-	-	-	0.1
150-175	-	-	-	0.1	0.0	0.6	0.1	-	-	-	0.0
175-250	-	-	-	0.0	0.0	0.7	0.1	-	-	-	0.0
300-375	-	-	-	0.0	0.0	-	-	-	-	-	0.0

Clay mineralogy

Depth (cm)	Chlorite	Feldspar	Gibbsite	Goethite	Halloysite	Hematite	Kaolinite	Mica / illite	Mixed-layer	Quartz	Smec	Vermiculite
0-30	-	-	-	very weak to weak	-	-	very strong	very weak to weak	weak to medium	very weak to weak	very weak to weak	-
30-60	-	-	-	very weak to weak	-	-	very strong	very weak	weak to medium	very weak to weak	very weak to weak	-
60-100	-	-	-	very weak to weak	-	-	very strong	very weak	weak to medium	very weak to weak	very weak to weak	-
100-150	-	-	-	very weak to weak	-	-	very strong	very weak	weak to medium	very weak to weak	very weak to weak	-
150-175	-	-	-	very weak to weak	-	-	very strong	very weak to weak	weak to medium	very weak to weak	weak to medium	-
175-250	-	-	-	very weak to weak	-	-	very strong	very weak	weak	very weak	weak to medium	-
300-375	-	-	-	very weak	-	-	very strong	very weak	very weak	very weak	strong to very strong	-

Profile description

Ap 0-30 cm	greyish brown (10YR 5/2, moist)silty clay,strong very coarse prismatic,extremely hard sticky very plastic,common (5-15%) fine distinct clear mottles (7.5 YR 5/6),few very fine pores,common very fine roots,moderately calcareous (2-10%),clear smooth boundary to,
Bi1 30-60 cm	(5Y 4.5/2.5, moist)silty clay,weak coarse angular blocky,friable sticky slightly plastic,broken moderately thick slickensides on pedfaces,common very fine pores,few very fine roots,moderately calcareous (2-10%),gradual smooth boundary to,
Bi2 60-100 cm	olive (5Y 5/3, moist)silty clay,moderate coarse wedge-shaped angular blocky,friable sticky slightly plastic,broken moderately thick slickensides on pedfaces,common very fine pores,common very fine roots,very few large spherical hard calcareous nodules,slightly calcareous (0-2%),diffuse smooth boundary to,
Bi3 100-150 cm	olive grey (5Y 5/2, moist)silty clay loam,moderate to strong very coarse wedge-shaped angular blocky,friable sticky very plastic,continuous moderately thick slickensides on pedfaces,common very fine pores,moderately calcareous (2-10%),gradual smooth boundary to,
Cg 150-175 cm	greyish brown (2.5Y 5/2, moist)silty clay loam,weak very coarse wedge-shaped angular blocky,friable sticky plastic,common (5-15%) medium distinct clear mottles (7.5 YR 5/6) and common (5-15%) medium distinct mottles (2.5 Y 6/1),common very fine pores,moderately calcareous (2-10%),
175-375 cm	greyish brown (2.5Y 5/2, moist)clay loam,many medium prominent mottles (7.5 YR 5/6),slightly calcareous (0-2%),

Kind 1 (parent material) ; Parker (eds), 1984	sediment, unconsolidated
Mode of accumulation or deposition of parent material	fluvial
Remarks on Parent Materials	"delta mort" Niger
Soil Depth	150cm
Texture of parent material	clayey

Major crops	rice
Land improvements ; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	draining
Main type of irrigation; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	paddy
Land use or vegetation in the immediate vicinity of the site	high level arable farming
Remarks on Land Use / Vegetation	VEGETATION: Irrigation system exists 40/50 years
Rotation scheme ; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	monoculture

Altitude	280m
Physiographic Unit	lower part of the plain
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.	alluvial plain
Slope	0%
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	imperfect
Dry From - To	0-10cm
Flooding frequency (FAO, 1986)	never
(Estimated) maximum (lower) depth to groundwater table	200cm
Depth to groundwater table	100cm
Kind of ground water table (USDA, 1979)	groundwater table observed
(Estimated) minimum (upper) depth to groundwater table	0cm
Moist From - To	10-50cm
Estimated permeability (class) of least permeable part of the profile	moderate
Estimated run off (class)	very slow
Wet From To	50-150cm

Evidence of alkali ; Soil Survey Manual USDA, 1951	moderately 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)	surface partly slaked, round smooth aggregates
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 Mali 02: Vertisol

Characteristics

Reference soil ML002: Vertisols

Classification