Reference soil Botswana 04: Calcisol

BW004

Calcisols occur in regions with distinct dry seasons, as well as in dry areas where carbonate-rich groundwater comes near the surface.

Characteristics

Soils having a (petro-)calcic horizon (horizon with accumulation of secondary calcium carbonates). In addition, they have no diagnostic horizons other than an ochric or cambic horizon, a calcareous argic horizon, or a gypsic horizon beneath a petrocalcic horizon.

Distribution of Calcisols (rough estimation supplied by soilgrids)

Reference soil BW004: Calcisols

LOCATION: 200 m West of main road to Gabarone VEGETATION: Acacia Mixed Woodland with A.nigerescens and A.totrilis BRIEF PROFILE DESCRIPTION: A moderatley deep, well drained, dark reddish brown snady clay loam with an epipedon of sandy loam texture, horizonation is gradual to clear, weak fine sub-angular blocky structure is confined to the top 33 cm. The soil reaction is slightly acid but becomes neutral to moderately alkaline in the subsoil. MORPHOLOGY: B1 Very fine and fine gravel increasing with depth. C Also pinkish white parts (5YR8/2, dry). The horizon has an appearance of weathered calcrete rock with granitic matrix; very hard (dry) but in some parts soft.

Classification

WRB 2006

WRB 1998

Luvic-Petric- Calcisol (Chromic)

Luvi-Endopetric- Calcisol

10-91 cm	argic horizon
91-100 cm	petrocalcic horizon

0-10 cm	ochric horizon
10-91 cm	argic horizon
91-100 cm	petrocalcic horizon

FAO-UNESCO-ISRIC 1988

FAO-UNESCO-ISRIC 1974

Chromi-Petric Calcisol

Calcic Xerosol petrocalcic

0-10 cm	ochric A horizon
10-91 cm	argic B horizon
91-100 cm	petrocalcic horizon
-	fluvic

0-10 cm	ochric A horizon
10-91 cm	argillic B horizon
91-100 cm	petrocalcic horizon

Other classification

USDA-NRCS (1999)	Aridic Rhodustalf ustic fine-loamy siliceous hyperthermic
USDA-SCS (1975)	Aridic Paleustalf ustic fine-loamy siliceous hyperthermic

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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
0-10	1	-	-	-	-	-	76	6.9	5.2	12.1	12.1
10-33	1	-	-	-	-	-	71	7.1	3.9	11	18
33-53	9	-	-	-	-	-	67.2	5.9	3.3	9.2	23.6
53-72	9	-	-	-	-	-	66.3	5.9	3.5	9.4	24.3
72-91	37	-	-	-	-	-	63.4	5.3	4.6	9.9	26.7
91-	58	-	-	-	-	-	-	6.8	4.5	11.3	34.1

Water retention characteristics

Depth (cm)	Bulk density kg/dm³	Spec. Surf. Area m²/g	COLE cm/cm	Water disp. clay %	Clay % w/w
0-10	-	-	-	-	12.1
10-33	-	-	-	-	18
33-53	-	-	-	-	23.6
53-72	-	-	-	-	24.3
72-91	-	-	-	-	26.7
91-	-	-	-	-	34.1

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
0-10	6.9	5.7	0.13	0.9	0.68	0.07	10	-	-	4.8	0.8	0.6	0.0	6.2
10-33	6.7	5.8	0.23	0.5	0.37	0.05	7	-	-	5.3	1.0	0.5	0.0	6.8
33-53	6.9	5.5	0.26	0.6	0.39	0.05	8	-	-	6.7	1.2	0.4	0.0	8.3
53-72	7.1	5.6	0.29	0.6	0.36	0.05	7	-	-	8.7	1.3	0.4	0.0	10.4
72-91	7.7	6.6	0.6	0.9	0.37	0.05	7	-	-	12.8	1.5	0.4	0.0	14.7
91-	8.3	7.1	0.98	39.4	0.33	0.06	6	-	-	17.1	1.1	0.5	0.0	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 %
0-10	76	8.2	68	2.4	-	-	0
10-33	85	8.0	44	1.3	-	-	0
33-53	88	9.4	40	1.4	-	-	0
53-72	95	10.9	45	1.3	-	-	0
72-91	96	15.3	57	1.3	-	-	0
91-	105	17.8	52	1.2	-	-	0

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
0-10	8.3	0.42	2.3	3.34	0.32	-	80.2	0.37
10-33	10.1	0.43	3.4	3.14	0.71	-	78.7	0.57
33-53	11.7	0.43	3.7	3.17	0.75	-	76.0	0.54
53-72	11.8	0.47	4.0	3.01	0.30	-	72.9	0.55
72-91	12.5	0.62	3.7	3.72	0.58	-	71.7	0.48
91-	9.6	11.11	3.3	2.27	0.57	-	53.9	0.49

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
0-10	5.7	4.3	0.04	0.10	16.4	92.7	13.9
10-33	4.7	4.9	0.04	0.06	13.2	61.5	10.9
33-53	5	5.6	0.03	0.10	11	54.6	9.2
53-72	4.6	6.1	0.04	0.03	10.5	48.4	8.6
72-91	5.3	7.0	0.03	0.04	9.7	51.5	8.2
91-	4.6	16.1	0.02	0.08	9.5	43.4	7.8

Profile description

Ah 0-10 cm	dark reddish brown (5YR 3/2, moist) dark reddish brown (5YR 3/4, dry)coarse sandy loam,moderate fine angular blocky,slightly hard friable non sticky non plastic,few fine and medium tubular pores,common very fine roots,slightly calcareous (0-2%),gradual smooth boundary to,
10-33 cm	dusky red (2.5YR 3/2, moist) (5YR 3.4/4, dry)coarse sandy loam,very weak fine angular blocky,slightly hard friable non sticky slightly plastic,few fine and medium tubular pores,common very fine and fine roots,few termite channels,slightly calcareous (0-2%),gradual smooth boundary to,
Bt1 33-53 cm	dark reddish brown (2.5YR 2/4, moist) dark reddish brown (2.5YR 3/4, dry)sandy clay loam,weak coarse angular blocky,hard friable slightly sticky slightly plastic,few fine and medium roots,very few fine gravel,few termite channels,slightly calcareous (0-2%),gradual smooth boundary to,
Bt2 53-72 cm	dark reddish brown (2.5YR 2/4, moist) dark reddish brown (2.5YR 3/4, dry)sandy clay loam slightly gravelly,structureless massive,hard friable slightly sticky slightly plastic,few fine tubular pores,few fine roots,few fine gravel,few termite channels,slightly calcareous (0-2%),clear wavy boundary to,
72-91 cm	dark reddish brown (2.5YR 2/4, moist) dark reddish brown (2.5YR 3/4, dry)sandy clay loam gravelly,structureless massive,hard friable slightly sticky non plastic,few fine and medium roots,few small soft calcareous concretions,common fine gravel,few termite channels,slightly calcareous (0-2%),extremely calcareous (>25%),clear wavy boundary to,
Ckm 91-91 cm	dark reddish brown (5YR 3/4, dry)sandy clay loam very gravelly,common fine gravel,extremely calcareous (>25%),

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

Altitude	1082m
Regional landform; McDonald, R.C., Isbell, R.F. et all, 1984; Australian soil and land survey Field Handbook, Inkata Press, Melbourne.	pediplain
Slope	0%
Topography; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	flat or almost flat

Drainage class ; FAO (2006) - Guidelines for soil description	well
Dry From - To	0-80cm
Moist From - To	80cm

Evidence of alkali ; Soil Survey Manual USDA, 1951	non-alkaline
Microrelief pattern	none
Rock outcrop class (FAO (2006) - Guidelines for soil description)	none
Evidence of salt; Soil Survey Manual USDA, 1951	non-saline

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Reference soil Botswana 04: Calcisol

Characteristics

Reference soil BW004: Calcisols

Classification