Reference soil Gabon 06: Acrisol

GA006

Acrisols occur dominantly in the wetter parts of the tropics and subtropics and the warm temperate regions in relatively young landscapes.

Characteristics

Soils having an argic horizon (a subsurface horizon with distinct higher clay content than the overlying horizon), which has a cation exchange capacity of less than 24 cmolc per kg in some part, either starting within 100 cm from the soil surface, or within 200 cm from the soil surface if the argic horizon is overlain by loamy sand or coarser textures throughout. They have a base saturation (total amount of Ca, Mg, K and Na with respect to the cation exchange capacity) of less than 50 percent in the major part between 25 and 100 cm from the soil surface

Distribution of Acrisols (rough estimation supplied by soilgrids)

Reference soil GA006: Acrisols

An imperfectly drained soil, derived from cretaceous sediments. The primary tropical forest has been burnt and replaced by herbs and grasses with some cultivated plots in-between (manioc, bananas, plantain). In the upper 25 cm some charcoal particles appear. The Btg2 horizon contains some quartz grains (3mm); vegetation; Afromomum giganteum, Dicronopteris linearis, Musanga cecropioides.

Classification

WRB 2006

WRB 1998

Gleyic-Cutanic- Acrisol (Alumic Epieutric Profondic)

Profondi-Endogleyic- Acrisol (Alumic)

25-150 cm	argic horizon
-	reducing conditions
-	gleyic colour pattern

FAO-UNESCO-ISRIC 1988

FAO-UNESCO-ISRIC 1974

Alumi-Gleyic Acrisol

Gleyic Acrisol

0-6 cm	ochric A horizon
25-150 cm	argic B horizon
-	gleyic

0-6 cm	ochric A horizon
25-150 cm	argillic B horizon
-	hydromorphic

Local classification:	Sol ferrallitique, fortement désaturé, apprauvi

Other classification

USDA-SCS (1975)

Tropudult udic 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
0-5	-	1.2	4.4	17.0	40.8	11.2	74.6	11.9	4.9	16.8	8.7
10-25	-	2.1	4.4	15.2	38.9	11.9	72.5	13.0	5.1	18.1	9.4
25-40	-	0.8	3.8	11.5	28.7	9.6	54.4	11.5	5.7	17.2	28.4
45-70	-	1.3	3.2	9.4	22.5	8.3	44.7	11.4	5.8	17.2	38.1
110-130	-	1.6	3.2	8.9	20.8	8.2	42.7	11.3	7.3	18.6	38.8

Water retention characteristics

Depth (cm)	Bulk density kg/dm³	Spec. Surf. Area m²/g	COLE cm/cm	Water disp. clay %	Clay % w/w
0-5	-	-	-	2.2	8.7
10-15	1.36	-	-	-	-
10-25	-	-	-	5.3	9.4
30-35	1.53	-	-	-	-
25-40	-	-	-	17.1	28.4
65-70	1.52	-	-	-	-
45-70	-	-	-	19.9	38.1
115-120	1.50	-	-	-	-
110-130	-	-	-	1.7	38.8

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
10-15	1.36	42.9	40.5	31.8	22.9	18.9	16.4	8.7	8.3
30-35	1.53	40.4	39.7	37.0	33.6	31.7	29.7	23.0	21.0
65-70	1.52	44.3	42.9	41.0	38.3	36.7	35.1	30.6	28.2
115-120	1.50	44.3	43.8	42.1	39.7	38.1	36.5	30.3	28.0

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
0-5	5.9	5.2	0.68	-	2.45	0.19	13	0.1	0.0	9.1	1.6	0.3	0.0	11
10-25	5.6	4.4	0.12	-	0.60	0.07	9	0.1	0.0	2.6	0.5	0.1	0.0	3.2
25-40	4.8	3.7	0.03	-	0.45	0.06	8	3.5	3.5	1.2	0.3	0.1	0.1	1.7
45-70	4.7	3.7	0.03	-	0.47	0.06	8	4.6	4.7	1.0	0.2	0.1	0.5	1.8
110-130	4.9	3.8	0.02	-	0.30	0.06	5	3.8	4.0	1.5	0.2	0.1	0.5	2.3

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 %
0-5	115	9.6	110	8.6	-	0	0
10-25	82	3.9	41	2.1	-	0	0
25-40	30	5.6	20	1.6	-	63	2
45-70	26	6.8	18	1.6	-	69	7
110-130	35	6.5	17	1.1	-	62	8

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
0-5	-	-	-	0.04	0.02	0.68	0.11	-	-	-	0.07
10-25	-	-	-	0.04	0.01	0.76	0.12	-	-	-	0.08
25-40	-	-	-	0.09	0.02	1.72	0.32	-	-	-	0.11
45-70	-	-	-	0.13	0.01	2.41	0.44	-	-	-	0.09
110-130	-	-	-	0.11	0.02	2.47	0.42	-	-	-	0.07

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
0-5	-	-	7.1	-	-	-	-	-	-
10-25	-	0.7	2.4	-	-	-	-	-	-

Clay mineralogy

Depth (cm)	Chlorite	Feldspar	Gibbsite	Goethite	Halloysite	Hematite	Kaolinite	Mica / illite	Mixed-layer	Quartz	Smec	Vermiculite
0-5	-	-	-	weak	-	-	strong to very strong	weak	very weak to weak	very weak to weak	-	-
10-25	-	-	-	weak	-	-	very strong	weak	very weak to weak	very weak to weak	-	-
25-40	-	-	-	weak	-	-	very strong	weak	very weak to weak	very weak to weak	-	-
45-70	-	-	-	weak	-	-	very strong	weak	very weak to weak	very weak to weak	-	-
110-130	-	-	-	weak	-	-	very strong	weak	very weak to weak	very weak to weak	-	-

Profile description

Ah 0-6 cm	very dark grey (10YR 3/1, moist)loamy sand,single grain to weak fine and medium subangular blocky,loose very friable slightly sticky non plastic,many micro to fine pores,many very fine and fine and many medium roots,non calcareous,clear smooth boundary to,
E 6-25 cm	yellowish brown (10YR 5/4, moist)loamy sand,weak fine and medium subangular blocky,very friable slightly sticky non plastic,many micro and very fine exped and inped pores,common very fine and fine roots,very few medium spherical hard ferruginous concretions,non calcareous,clear irregular boundary to,
BA 25-42 cm	yellowish brown (10YR 5/6, moist)sandy clay loam,weak medium subangular blocky,firm sticky plastic,common (5-15%) fine distinct clear mottles (5 YR 5/6),many micro to fine exped and inped pores,few very fine and fine roots,non calcareous,gradual smooth boundary to,
Btg1 42-85 cm	yellowish brown (10YR 5/8, moist)clay,moderate coarse angular blocky,firm sticky plastic,many (15-40%) medium distinct clear mottles (5 YR 5/6),broken moderately thick clay and humus cutans,many micro pores and common fine exped and inped pores,few very fine and fine roots,non calcareous,diffuse smooth boundary to,
Btg2 85-150 cm	strong brown (7.5YR 5/8, moist)clay,moderate coarse angular blocky,firm sticky plastic,many (15-40%) medium distinct clear mottles (5 YR 5/8) and common (5-15%) fine faint diffuse mottles (10 YR 6/4),broken moderately thick clay and humus cutans,many micro pores and common fine exped and inped interstitial pores,few very fine and fine roots,very few fine gravel fresh quartz fragments,non calcareous,

Kind 1 (parent material) ; Parker (eds), 1984	sedimentary rock
Mode of accumulation or deposition of parent material	unconsolidated, unspecified
Remarks on Parent Materials	Lower Cretaceous
Texture of parent material	clayey
Weathering Resistance	poor
General characterization of the status of weathering of solid rock	highly

Major crops	cassava
Land improvements ; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	burning
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	shifting cultivation
Remarks on Land Use / Vegetation	VEGETATION: Afromomum giganteum, Dicronopteris linearis, Musanga cecropiodes
Rotation scheme ; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	shifting
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)	grassland

Altitude	150m
Physiographic Unit	upland
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	8%
Slope Aspect	south
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	imperfect
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)	very 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
Microrelief Height: variation in height	150
Micro relief type: small-scale differences in relief in the direct vicinity of the site (FAO, 1986)	termite/ant mounds
Microrelief pattern	isolated
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 Gabon 06: Acrisol

Characteristics

Reference soil GA006: Acrisols

Classification