Reference soil Gabon 05: Plinthosol

GA005

Plinthosols occur mainly in the moist tropical regions in low-lying positions where iron from the soil and adjacent uplands is accumulating.

Characteristics

Soils having either a petroplinthic horizon within 50 cm from the soil surface, or a plinthic horizon which either starts within 50 cm from the soil surface, or within 100 cm from the soil surface if it underlies an albic horizon or a horizon with stagnic properties.

Distribution of Plinthosols (rough estimation supplied by soilgrids)

Reference soil GA005: Plinthosols

A well drained deep soil (125-180cm) on an erosional plain between two ridges (closed basin in karst landscape). The land is used for hunting and is burnt anually. There are charcoal fragments in upper horizon and about 10 % of organic matter in Bcs. With increasing depth the amount of ironstone (goethite) becomes dominant (up to stone and boulder size); vegetation: immenocardia; additional climatic information: insolation (hours).

Classification

WRB 2006

WRB 1998

Acric-Pisoplinthic- Plinthosol (Hyperdystric Clayic)

Hyperdystri-Pisoplinthic- Acrisol

25-100 cm	argic horizon
50-100 cm	pisoplinthic horizon

FAO-UNESCO-ISRIC 1988

FAO-UNESCO-ISRIC 1974

Ferric Acrisol skeletic

Xanthic Ferralsol petric

0-22 cm	ochric A horizon
22-100 cm	argic B horizon

0-22 cm	ochric A horizon
22-100 cm	oxic B horizon

Local classification:	Sol ferrallitique jaune, fortement désaturé

Other classification

USDA-SCS (1975)

Haplorthox udic clayey-skeletal kaolinitic isohyperthermic

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	2	2.9	4.4	8.3	19.3	10.7	45.6	11.7	4.4	16.1	38.2
25-50	32	5.9	4.2	5.3	14.2	9.8	39.4	8.8	4.4	13.2	47.2
60-90	70	6.6	4.8	4.1	9.5	11.2	36.2	10.0	2.4	12.4	51.3
-	90	-	-	-	-	-	-	-	-	-	-

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	-	-	-	14.2	38.2
25-50	-	-	-	14.8	47.2
60-90	-	-	-	0.0	51.3

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	5.1	4.0	0.05	-	2.22	0.12	19	2.2	1.8	0.4	0.2	0.2	0.1	0.9
25-50	4.1	3.9	0.03	-	1.09	0.07	16	2.2	2.0	0.2	0.1	0.1	0.0	0.4
60-90	-	-	-	-	0.69	0.08	9	1.9	1.3	0.0	0.0	0.0	0.0	-
-	-	-	-	-	-	-	-	1.7	1.3	0.2	0.1	0.1	0.1	0.5

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	13	7.1	19	7.8	-	25	1
25-50	8	5.1	11	3.8	-	39	0
60-90	-	3.7	7	2.4	-	35	0
-	10	4.8	-	-	-	27	2

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	-	-	-	0.17	0.02	2.25	0.52	-	-	-	0.10
25-50	-	-	-	0.15	0.02	3.14	0.71	-	-	-	0.06
60-90	-	-	-	0.13	0.01	3.08	0.68	-	-	-	0.04
-	-	-	-	0.12	0.02	2.97	0.53	-	-	-	0.05

Depth (cm)	CaSO4.2H2O %	P Bray mg/kg	P Olsen mg/kg	pH CaCl2	clay_noncarbonate % w/w	clay_carbonate % w/w	phosphorus4 mg/kg	phosphorus1 mg/kg	total_sulfur % w/w
0-20	-	-	4.7	-	-	-	-	-	-
25-50	-	-	2.2	-	-	-	-	-	-

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
25-50	36.2	32.3	13.7	0.00	0.36	0.78	0.08	2.09

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
25-50	0.01	0.20	12.8	98.52	1.9	7	1.5	3.7

Clay mineralogy

Depth (cm)	Chlorite	Feldspar	Gibbsite	Goethite	Halloysite	Hematite	Kaolinite	Mica / illite	Mixed-layer	Quartz	Smec	Vermiculite
0-20	-	very weak to weak	-	weak to medium	-	-	very strong	very weak to weak	very weak to weak	very weak	-	-
25-50	-	very weak to weak	-	weak to medium	-	-	very strong	very weak to weak	very weak to weak	very weak	-	-
60-90	-	very weak to weak	-	weak to medium	-	-	very strong	very weak to weak	very weak to weak	very weak to weak	-	-
-	-	very weak to weak	-	weak to medium	-	-	very strong	very weak to weak	very weak to weak	very weak to weak	-	-

Sand mineralogy

Depth (cm)	Heavy Frac. sand % w/w	K-Feldspar % w/w	Light Fra. sand % w/w	Opaque % w/w	Plagioclase % w/w	Quartz % w/w
60-90	0.3	-	99.7	-	-	100

Profile description

Ah 0-22 cm	dark brown (10YR 3/3, moist)slightly gravelly clay,medium and coarse subangular blocky,slightly hard friable sticky plastic,many micro to fine exped and inped pores,many very fine and fine and many medium roots,very few medium irregular hard ferruginous concretions,non calcareous,clear smooth boundary to,
ABoc 22-50 cm	yellowish brown (10YR 5/4, moist)very gravelly clay,fine and medium subangular blocky,friable sticky plastic,many micro to fine exped pores,common very fine and fine roots,very frequent medium irregular hard ferruginous concretions,non calcareous,gradual irregular boundary to,
Boc 50-100 cm	yellowish brown (10YR 5/8, moist)very gravelly clay,porous massive,friable sticky plastic,many micro to fine exped interstitial pores,few very fine and fine roots,very frequent large irregular hard ferruginous concretions,non calcareous,

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

Land improvements ; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	burning
Land use or vegetation in the immediate vicinity of the site	(semi-)natural vegetation
Remarks on Land Use / Vegetation	VEGETATION: Immenocardia. LAND USE: Burnt annually
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)	semi-deciduous shrub

Altitude	150m
Physiographic Unit	valley between two ridges
Physiographic position of the site	upper slope
Regional landform; McDonald, R.C., Isbell, R.F. et all, 1984; Australian soil and land survey Field Handbook, Inkata Press, Melbourne.	plain
Slope	3%
Slope Aspect	west
Form of the slope surrounding the site	convex
Topography; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	undulating

Drainage class ; FAO (2006) - Guidelines for soil description	well
Flooding frequency (FAO, 1986)	never
Kind of ground water table (USDA, 1979)	no groundwater table observed
Estimated permeability (class) of least permeable part of the profile	moderate
Estimated run off (class)	slow

Evidence of alkali ; Soil Survey Manual USDA, 1951	non-alkaline
Surface cracking	no cracks observed
Slaking of aggregates by tillage, rainfall or frost (USDA/SCS, 1979)	no surface slaking/crusting observed
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)	fairly stony

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Reference soil Gabon 05: Plinthosol

Characteristics

Reference soil GA005: Plinthosols

Classification