Reference soil Gabon 03: Acrisol

GA003

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 GA003: Acrisols

A well drained, deep rooting soil (125-180 cm), derived from precambrian material (schists and sanstone) that varies considerably in composition. On the surface there is a micro-relief of earthworm heaps (2 cm); in the B horizons common reddish yellowish to yellowish mottles appear. Particles of parent material can be found in Ah2, Bns and BC. Apart from patchy clay-iron cutans, clay-humus cutans and humus cutans cann be found in Bws and Bns. In these horizons there are tongues of organic material, filled in the space between the structural elements. The land is savannah, used for hunting and is mainly consisting of herbs and grasses with spots of dense forest; vegetation: pobeguinea sp., hymenocardia acida, palmyra sp.; additional climate data: insolation (h).

Classification

WRB 2006

WRB 1998

Umbric-Pisoplinthic-Cutanic- Acrisol (Alumic Humic Profondic)

Umbrihumi-Pisoplinthic- Acrisol (Profondic Alumic)

0-25 cm	umbric horizon
25-150 cm	argic horizon
90-150 cm	pisoplinthic horizon

FAO-UNESCO-ISRIC 1988

FAO-UNESCO-ISRIC 1974

Alumi-Humic Acrisol

Humic Acrisol petric

0-25 cm	umbric A horizon
25-150 cm	argic B horizon
-	strongly humic

0-25 cm	umbric A horizon
25-150 cm	argillic B horizon

Other classification

USDA-SCS (1975)

Umbriorthox udic 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
0-10	-	0.5	0.9	0.9	6.6	8.6	17.5	12.2	22.8	35	47.5
10-25	-	0.1	0.3	0.6	6.2	8.5	15.7	11.9	21.8	33.7	50.7
30-70	-	0.2	0.4	0.5	3.6	5.7	10.4	7.4	20.4	27.8	61.9
90-120	75	3.7	1.1	0.5	2.1	3.7	11.1	7.8	14.6	22.4	66.5
130-150	8	1.6	0.9	0.4	1.5	2.2	6.6	5.8	28.5	34.3	59.1

Water retention characteristics

Depth (cm)	Bulk density kg/dm³	Spec. Surf. Area m²/g	COLE cm/cm	Water disp. clay %	Clay % w/w
5-10	1.05	-	-	-	-
0-10	-	-	-	20.7	47.5
10-25	-	-	-	28.3	50.7
17-22	1.19	-	-	-	-
30-70	-	-	-	40.6	61.9
65-70	1.33	-	-	-	-
90-120	-	-	-	1.2	66.5
130-150	-	-	-	6.7	59.1

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
5-10	1.05	56.4	55.9	53.4	50.5	48.1	44.8	33.0	27.1
17-22	1.19	52.8	52.7	50.8	48.0	46.0	43.7	34.1	28.6
65-70	1.33	49.8	48.8	47.2	45.6	45.1	44.3	42.0	39.6

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	4.7	3.6	0.14	-	5.25	0.29	18	6.9	6.0	2.3	0.3	0.4	0.0	3
10-25	4.8	3.8	0.04	-	3.46	0.22	16	8.0	7.3	0.6	0.0	0.2	0.0	0.8
30-70	4.6	3.8	0.03	-	0.75	0.13	6	8.2	8.0	0.4	0.0	0.1	0.0	0.5
90-120	-	-	-	-	0.26	0.13	2	9.0	8.2	0.0	0.1	0.2	0.1	0.4
130-150	4.8	3.8	0.02	-	0.28	0.11	3	8.5	8.0	0.2	0.0	0.1	0.0	0.3

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 %
0-10	14	20.8	44	18.4	-	29	0
10-25	5	15.4	30	12.1	-	47	0
30-70	5	10.2	16	2.6	-	78	0
90-120	3	12.3	18	0.9	-	67	1
130-150	3	10.6	18	1.0	-	75	0

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
0-10	-	-	-	0.30	0.03	2.20	0.51	-	-	-	0.23
10-25	-	-	-	0.37	0.02	2.32	0.56	-	-	-	0.38
30-70	-	-	-	0.21	0.02	2.69	0.48	-	-	-	0.09
90-120	-	-	-	0.20	0.02	3.38	0.47	-	-	-	0.10
130-150	-	-	-	0.15	0.02	3.44	0.36	-	-	-	0.10

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
0-10	-	-	16.8	-	-	-	-	-	-
10-25	-	-	10.2	-	-	-	-	-	-
30-70	-	-	0.9	-	-	-	-	-	-

Clay mineralogy

Depth (cm)	Chlorite	Feldspar	Gibbsite	Goethite	Halloysite	Hematite	Kaolinite	Mica / illite	Mixed-layer	Quartz	Smec	Vermiculite
0-10	-	-	-	weak	-	-	very strong	medium to strong	-	very weak	-	-
10-25	-	-	-	weak	-	-	very strong	strong	very weak	very weak	-	-
30-70	-	-	-	weak	-	-	very strong	medium to strong	very weak	very weak	-	-
90-120	-	-	-	weak	-	-	very strong	strong	very weak	very weak	-	-
130-150	-	-	-	weak	-	-	very strong	strong	very weak	very weak	-	-

Profile description

Ah1 0-10 cm	black (10YR 2/1, moist)clay,strong fine and medium subangular blocky,friable sticky plastic,many micro to medium exped and inped pores,many very fine and fine roots,non calcareous,clear wavy boundary to,
Ah2 10-25 cm	very dark greyish brown (10YR 3/2, moist)clay,strong medium angular blocky,friable sticky plastic,very fine few very fine exped and inped pores,many very fine and fine roots,very few medium gravel schist few sandstone fragments,non calcareous,abrupt irregular boundary to,
Bo1 25-80 cm	yellowish brown (10YR 5/8, moist)clay,moderate coarse angular blocky to weak fine angular blocky,firm sticky plastic,common (5-15%) fine faint clear mottles,patchy thin clay and sesquioxide cutans,very fine and few micro very fine tubular pores,common very fine and fine common medium roots,very few medium irregular hard ferruginous concretions,non calcareous,abrupt irregular boundary to,
Bo2 80-125 cm	strong brown (7.5YR 5/6, moist)very gravelly clay,moderate fine angular blocky,firm sticky plastic,common (5-15%) fine faint clear mottles,patchy moderately thick clay and humus cutans,few very fine micro inped tubular pores and few to common very fine exped interstitial pores,few very fine and fine roots,few medium irregular hard ferruginous concretions,common medium gravel sandstone and common medium gravel schist fragments,non calcareous,clear irregular boundary to,
125-150 cm	yellowish red (5YR 5/6, moist)gravelly clay,moderate fine angular blocky,firm sticky plastic,common (5-15%) fine faint clear mottles,patchy thin clay and sesquioxide cutans,few very fine micro inped tubular pores and very fine few very fine exped interstitial pores,few very fine and fine roots,few medium gravel sandstone few medium gravel schist fragments,non calcareous,

Kind 1 (parent material) ; Parker (eds), 1984	sandstone
Kind 2 (parent material) (second entry); Parker (eds), 1984	schist
Mode of accumulation or deposition of parent material	residual material
Mode of accumulation or deposition of parent material (second entry)	residual material
Remarks on Parent Materials	Francevillien (Middle Precambrium), série sédimentaire non métamorphique, grès de Les Pakas
Texture of parent material	clayey
Texture of parent material (second entry)	clayey
Weathering Resistance	high
Weathering Resistance (second entry)	moderate
General characterization of the status of weathering of solid rock	highly
General characterization of the status of weathering of solid rock (second entry)	highly

Land improvements ; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	burning
Land use or vegetation in the immediate vicinity of the site	hunting and fishing
Remarks on Land Use / Vegetation	VEGETATION: Savannah with parts of dense forest; main species herbs and grasses with spots of dense forest; main species: Pobeguinea sp., Hymenocardia acida and Palmyra sp. LAND USE: Burnt annually
Major vegetation type; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	semi-deciduous shrub

Altitude	350m
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.	hill
Slope	30%
Slope Aspect	south-west
Topography; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	hilly

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)	rapid

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)	none

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Reference soil Gabon 03: Acrisol

Characteristics

Reference soil GA003: Acrisols

Classification