Reference soil Namibia 09: Vertisol

NA009

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

Classification

WRB 2006

Grumic Calcic Vertisols (Pellic )

20-40	cambic horizon
-	secondary carbonates horizon
40-110	vertic horizon

WRB 1998

calcic horizon Pelli Vertisols

FAO-UNESCO-ISRIC 1988

Calcari-Eutric Vertisols

-	calcareous horizon
-	slickensides horizon
0-20 cm	ochric A horizon
20-110 cm	cambic B horizon

FAO-UNESCO-ISRIC 1974

Pellic Vertisols

-	slickensides horizon
-	vertic horizon
0-20 cm	ochric A horizon
20-110 cm	cambic B horizon

Other classification

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

Location:

Grootfontein District, 30km E of Tsumeb, Farm Smithfield, lot 541

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Physical

Particle size distribution:

Depth (cm)	Clay % weight/weight	coarse sand % weight/weight	coarse silt % weight/weight	fine sand % weight/weight	fine silt % weight/weight	Gravel % volume/volume	medium sand % weight/weight	Total sand % weight/weight	Total silt % weight/weight	very coarse sand % weight/weight	very fine sand % weight/weight
0-20	30.1	1.5	1.8	30.6	22.2	5	2.5	45.9	24	1.7	9.6
20-40	33.8	1.3	2.2	27.0	24.4	7	1.5	39.8	26.6	1.5	8.5
40-60	34.0	1.6	2.8	25.4	25.1	2	1.3	38.1	27.9	2.2	7.6
60-80	34.7	2.0	3.0	24.5	23.5	3	1.6	38.8	26.5	2.2	8.5
80-100	37.4	1.3	3.4	23.9	22.9	3	1.2	36.3	26.3	1.2	8.7
100-115	31.5	1.3	6.1	22.2	28.2	-	1.0	34.2	34.3	2.3	7.4

Other physical data

Depth (cm)	Bulk density kg/dm³	Clay % weight/weight	COLE cm/cm	Spec. Surf. Area m²/g	Water disp. clay %
0-20	-	30.1	-	-	-
20-40	-	33.8	-	-	-
40-60	-	34.0	-	-	-
60-80	-	34.7	-	-	-
80-100	-	37.4	-	-	-
100-115	-	31.5	-	-	-

Chemical characteristics:

Depth (cm)	C % weight/weight	Ca cmol(c)/kg	CaCO3 % weight/weight	C / N unitless	EC 1: 2.5 mS/cm	Exch. Acid cmol(c)/kg	Exch. Al cmol(c)/kg	K cmol(c)/kg	Mg cmol(c)/kg	N %	Na cmol(c)/kg	pH H2O unitless	pHKCl unitless	Sum Cations cmol(c)/kg
0-20	1.02	30.5	8.1	20	0.22	-	-	0.4	8.8	0.05	0.4	8.3	7.0	40.1
20-40	0.72	30.5	7.4	24	0.24	-	-	0.3	12.5	0.03	0.2	8.5	7.0	43.5
40-60	0.67	23.5	7.2	22	0.24	-	-	0.3	15.2	0.03	0.2	8.5	7.1	39.2
60-80	0.67	24.7	8.0	22	0.27	-	-	0.3	16.7	0.03	0.2	8.6	7.1	41.9
80-100	0.62	23.5	5.8	21	0.30	-	-	0.3	18.7	0.03	0.5	8.7	7.1	43
100-115	0.56	24.7	9.9	19	0.32	-	-	0.3	20.6	0.03	0.7	8.7	7.2	46.3

Depth (cm)	Al sat. %	Base sat. %	CEC clay cmol(c)/kg	CEC org cmol(c)/kg	CEC soil cmol(c)/kg	ECEC cmol(c)/kg	ESP %
0-20	-	137	97	3.6	29.2	-	1
20-40	-	130	99	2.5	33.5	-	1
40-60	-	106	109	2.3	37.0	-	1
60-80	-	119	101	2.3	35.1	-	1
80-100	-	112	102	2.2	38.3	-	1
100-115	-	123	120	2.0	37.7	-	2

Depth (cm)	Al d % weight/weight	Al o % weight/weight	Al p % weight/weight	C p % weight/weight	Fe d % weight/weight	Fe o % weight/weight	Fe p % weight/weight	ODOE unitless	pH NaF unitless	P Retention %	Si o % weight/weight
0-20	-	-	-	-	0.30	-	-	-	-	-	-
20-40	-	-	-	-	0.28	-	-	-	-	-	-
40-60	-	-	-	-	0.30	-	-	-	-	-	-
60-80	-	-	-	-	0.30	-	-	-	-	-	-
80-100	-	-	-	-	0.28	-	-	-	-	-	-
100-115	-	-	-	-	0.30	-	-	-	-	-	-

Clay mineralogy:

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

Profile description:

Apk 0-20 cm	(2.5Y 4.5/1, dry) (2.5Y 4/1, moist)clay,strong very fine granular,hard friable very sticky very plastic,moderately porous (40-60 vol%),few fine roots,few small irregular soft calcareous nodules,moderately calcareous (2-10%),abrupt wavy boundary to,
ABk 20-40 cm	(2.5Y 4.5/1, dry) (2.5Y 3.5/1, moist)clay,weak coarse prismatic parting to weak medium subangular blocky,hard friable very sticky very plastic,few very fine discontinuous tubular pores,few fine roots,few small irregular soft calcareous nodules,moderately calcareous (2-10%),gradual smooth boundary to,
BAki 40-80 cm	(2.5Y 4.5/1, dry) (2.5Y 3.5/1, moist)clay,moderate coarse prismatic parting to moderate medium angular blocky,very hard firm very sticky very plastic,patchy slickensides,few discontinuous inped tubular random pores,few small irregular soft calcareous nodules,moderately calcareous (2-10%),gradual smooth boundary to,
Bki 80-110 cm	(2.5Y 4.5/1, dry) (2.5Y 3.5/1, moist)clay,weak coarse prismatic parting to strong MF wedge-shaped angular blocky,very hard firm very sticky very plastic,continuous slickensides,few very fine discontinuous inped tubular random pores,few small irregular soft calcareous nodules,moderately calcareous (2-10%),

Weathering Resistance	moderate
General characterization of the status of weathering of solid rock	partially or moderately
Texture of parent material	clayey
Mode of accumulation or deposition of parent material	lacustrine sediments
Kind 1 (parent material) ; Parker (eds), 1984	dolomitic limestone

Occurrence of soil aggradation (McDonald et al., 1984)	absent
Slope stability	stable	basin

Altitude	1300m
Topography; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	undulating
Physiographic Unit	basin floor
Slope	0%
Physiographic position of the site	flat
Form of the slope surrounding the site	straight
Regional landform; McDonald, R.C., Isbell, R.F. et all, 1984; Australian soil and land survey Field Handbook, Inkata Press, Melbourne.	basin

Surface cracking	large cracks (width more than 1 cm, or depth more than 50 cm)
Evidence of salt; Soil Survey Manual USDA, 1951	non-saline
Microrelief pattern	none
Evidence of alkali ; Soil Survey Manual USDA, 1951	non-alkaline
Rock outcrop class (FAO (2006) - Guidelines for soil description)	none
Surface stoniness class (FAO (2006) - Guidelines for soil description)	none
Slaking of aggregates by tillage, rainfall or frost (USDA/SCS, 1979)	no surface slaking/crusting observed

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Reference soil Namibia 09: Vertisol

Classification