Reference soil South Africa 21: Alisol

ZA021

Alisols occur in the tropics and subtropics, and in the warm temperate regions of the world in relatively young landscapes. The high level of exchangeable aluminium in these soils is caused by rapid weathering of secondary high-activity clays such as vermiculite and smectite.

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 24 cmolc per kg clay or more, and which starts either 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 "alic" properties (high content of exchangeable aluminium) in the major part between 25 and 100 cm from the soil surface; moreover, only such diagnostic horizons as an ochric, albic, andic, ferric, nitic, plinthic, or vertic horizon are present.

Distribution of Alisols (rough estimation supplied by soilgrids)

Reference soil ZA021: Alisols

BRIEF CHARACTERIZATION OF THE SOIL: A very dark reddish brown topsoil, rich in organic matter and extending down to 90 cm, overlies, via a transitional horizon, a red subsoil with below 150 cm fragments of weathering arkose. The soil is very porous throughout and shows in many parts a characteristic polyhedral ("nut") structure. Top 18 cm are disturbed by ploughing. PARENT ROCK: Table Mountain sandstone Formation. ADDITIONAL NOTES ON PROFILE DESCRIPTION: ABh - mottles are dark. The soil shows (on drying) vertical cracks (2 mm wide), 10-20 cm apart. below 150cm: white mottles (weathering Table Mountain Sandstone).

Classification

WRB 2006

WRB 1998

Umbric- Alisol (Humic Hyperdystric Profondic Clayic)

Humi-Umbric- Nitisol

0-90 cm	umbric horizon
20-160 cm	argic horizon

FAO-UNESCO-ISRIC 1988

FAO-UNESCO-ISRIC 1974

Umbri-Humic Nitisol

Humic Nitosol

0-90 cm	umbric A horizon
20-160 cm	argic B horizon

0-90 cm	umbric A horizon
20-160 cm	argillic B horizon

Local classification:	Inanda Form, Glenariff Family

Other classification

USDA-NRCS (1999)	Typic Palehumult
USDA-SCS (1975)	Typic Palehumult udic fine mixed thermic

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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
0-20	-	0.2	2.2	12.5	31.1	6.4	52.4	9.4	16.7	26.1	21.5
20-40	-	0.4	4.2	22.7	21.7	3.5	52.5	5.8	9.3	15.1	31.9
40-60	-	0.3	3.4	18.9	20.9	2.9	46.4	5.8	7.6	13.4	40.2
60-80	-	0.3	2.9	16.4	20.8	2.6	43	7.0	6.6	13.6	43.4
80-100	-	0.5	3.6	18.4	20.1	2.6	45.2	5.5	5.7	11.2	43.6
100-120	-	0.3	2.7	15.1	18.8	3.0	39.9	4.9	6.0	10.9	49.2
120-140	-	0.7	2.3	11.7	16.2	2.9	33.8	9.6	7.2	16.8	52.4
140-160	4	1.9	3.5	14.0	13.9	3.1	36.4	8.5	8.3	16.8	46.8
160-180	1	2.5	4.2	20.9	13.6	2.6	43.8	5.3	13.8	19.1	37.1

Water retention characteristics

Depth (cm)	Bulk density kg/dm³	Spec. Surf. Area m²/g	COLE cm/cm	Water disp. clay %	Clay % w/w
0-20	-	-	-	-	21.5
20-40	-	-	-	-	31.9
40-60	-	-	-	-	40.2
60-80	-	-	-	-	43.4
80-100	-	-	-	-	43.6
100-120	-	-	-	-	49.2
120-140	-	-	-	-	52.4
140-160	-	-	-	-	46.8
160-180	-	-	-	-	37.1

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
0-20	5.1	4.3	0.06	-	2.46	0.13	19	1.6	0.9	1.8	0.5	0.1	0.0	2.4
20-40	5.6	4.5	0.06	-	2.87	0.14	21	0.8	0.2	2.1	1.2	0.1	0.2	3.6
40-60	5.4	4.4	0.04	-	2.48	0.12	21	1.5	0.9	1.5	0.9	0.0	0.2	2.6
60-80	5.1	4.2	0.04	-	2.00	0.08	25	2.2	1.6	1.5	0.4	0.1	0.2	2.2
80-100	5.1	4.2	0.04	-	1.76	0.05	35	2.1	1.3	1.5	0.3	0.0	0.2	2
100-120	5.1	4.3	0.03	-	1.08	0.05	22	1.5	0.9	1.0	0.2	0.1	0.2	1.5
120-140	5.4	4.6	0.03	-	0.52	0.04	13	0.2	0.0	1.0	0.3	0.0	0.0	1.3
140-160	5.3	4.8	0.03	-	0.40	0.03	13	0.2	0.0	1.5	0.3	0.1	0.2	2.1
160-180	5.1	4.5	0.03	-	0.23	0.02	12	0.3	0.0	1.0	0.3	0.0	0.0	1.3

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 %
0-20	13	19.1	89	8.6	-	5	0
20-40	17	20.9	66	10.0	-	1	1
40-60	11	24.5	61	8.7	-	4	1
60-80	10	22.3	51	7.0	-	5	1
80-100	9	22.3	51	6.2	-	4	1
100-120	10	15.1	31	3.8	-	0	1
120-140	10	12.9	25	1.8	-	0	0
140-160	19	11.1	24	1.4	-	0	2
160-180	12	10.7	29	0.8	-	0	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
0-20	-	-	-	0.5	0	2.4	0.7	-	-	-	0.2
20-40	-	-	-	0.4	0	2.8	0.7	-	-	-	0.2
40-60	-	-	-	0.6	0	3.3	0.8	-	-	-	0.2
60-80	-	-	-	0.6	0	3.5	0.9	-	-	-	0.2
80-100	-	-	-	0.6	0	3.7	1.0	-	-	-	0.2
100-120	-	-	-	0.5	0.1	4.3	1.0	-	-	-	0.2
120-140	-	-	-	0.4	0	4.4	0.7	-	-	-	0.2
140-160	-	-	-	0.4	0	3.9	0.3	-	-	-	0.2
160-180	-	-	-	0.3	0	3.9	0.3	-	-	-	0.2

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
0-20	26.0	36.9	14.4	0.01	0.45	0.18	-	1.37
20-40	28.3	39.2	15.3	0.01	0.49	0.18	-	1.50
40-60	26.5	38.2	15.5	0.01	0.54	0.17	-	1.44
60-80	25.6	34.6	13.4	0.00	0.34	0.16	-	1.26
80-100	26.1	38.3	15.6	0.00	0.45	0.19	-	1.46
100-120	25.6	38.5	15.2	0.00	0.35	0.20	-	1.32
120-140	24.6	38.9	15.7	0.00	0.31	0.26	-	1.35
140-160	27.2	39.1	15.0	0.00	0.33	0.29	-	1.27
160-180	30.4	38.3	14.1	0.00	0.31	0.38	-	1.22

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
0-20	0.03	0.24	18.3	97.88	1.2	4.8	1	4
20-40	0.03	0.20	18	103.21	1.2	4.9	1	4
40-60	0.03	0.17	18.5	-	1.2	4.6	0.9	3.9
60-80	0.02	0.15	25.9	101.43	1.3	5.1	1	4
80-100	0.02	0.14	18.4	100.66	1.2	4.4	0.9	3.8
100-120	0.02	0.16	18.7	100.05	1.1	4.5	0.9	4
120-140	0.02	0.16	18.4	99.7	1.1	4.2	0.9	3.9
140-160	0.02	0.16	17.7	101.07	1.2	4.8	0.9	4.1
160-180	0.02	0.12	16.8	101.65	1.3	5.7	1.1	4.3

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
0-20	10.8	0.04	4.9	0.08	0.05	-	74.3	0.89
20-40	12.4	0.07	5.5	0.09	0.02	-	71.9	0.97
40-60	12.9	0.03	5.7	0.09	0.00	-	72.1	0.93
60-80	15.1	0.01	6.6	0.10	0.04	-	69.0	1.03
80-100	15.9	0.01	6.9	0.10	0.00	-	68.1	1.04
100-120	18.6	0.00	8.2	0.20	0.00	-	62.6	1.11
120-140	17.7	0.00	7.2	0.25	0.02	-	67.1	1.00
140-160	16.5	0.00	7.2	0.12	0.00	-	67.8	1.04
160-180	16.3	0.00	7.4	0.16	0.05	-	68.4	1.01

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
0-20	3.5	9.2	0.01	0.03	11.7	40.4	9.1
20-40	3.5	10.1	0.01	0.04	9.8	34.8	7.7
40-60	3.5	9.6	0.01	0.03	9.5	33.6	7.4
60-80	3.6	10.0	0.01	0.03	7.8	27.8	6.1
80-100	3.6	10.0	0.02	0.03	7.3	26.2	5.7
100-120	3.6	8.7	0.02	0.04	5.7	20.3	4.5
120-140	3.9	7.7	0.01	0.03	6.4	24.8	5.1
140-160	3.6	9.2	0.01	0.03	7	25	5.5
160-180	3.5	9.3	0.06	0.06	7.1	24.6	5.5

Clay mineralogy

Depth (cm)	Chlorite	Feldspar	Gibbsite	Goethite	Halloysite	Hematite	Kaolinite	Mica / illite	Mixed-layer	Quartz	Smec	Vermiculite
0-20	-	-	weak to medium	weak to medium	-	-	weak to medium	-	weak to medium	very weak to weak	-	-
20-40	-	-	weak to medium	weak to medium	-	-	weak to medium	-	weak to medium	very weak to weak	-	-
40-60	-	-	weak to medium	weak to medium	-	-	weak to medium	-	weak to medium	very weak to weak	-	-
60-80	-	-	weak to medium	weak to medium	-	very weak	weak to medium	-	weak to medium	very weak to weak	-	-
80-100	-	-	weak to medium	weak to medium	-	very weak	weak to medium	-	weak to medium	very weak to weak	-	-
100-120	-	-	weak to medium	weak to medium	-	very weak	weak to medium	-	weak to medium	very weak to weak	-	-
120-140	-	-	weak to medium	weak to medium	-	very weak	weak to medium	-	weak to medium	very weak to weak	-	-
140-160	-	-	weak to medium	weak to medium	-	very weak	medium to strong	-	weak to medium	-	-	-
160-180	-	-	weak to medium	weak to medium	-	very weak	medium to strong	-	weak to medium	-	-	-

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
0-20	0.9	-	99.1	77	-	100
40-60	0.4	-	99.6	51	-	100
100-120	0.5	-	99.5	60	-	100
140-160	1.2	-	98.8	70	-	100

Minerals

Depth (cm)	Anatase % w/w	Andalusite % w/w	Apatite % w/w	Augite % w/w	Biotite % w/w	Hornblende (basaltic) % w/w
0-20	20	-	-	-	-	-
40-60	19	-	-	-	-	-
100-120	23	-	-	-	-	-
140-160	28	-	-	-	-	-

Depth (cm)	Grenate % w/w	Grossular % w/w	Muscovite % w/w	Rutile % w/w	Sillimanite % w/w	Spinel % w/w
0-20	-	-	-	35	-	-
40-60	1	-	-	34	-	-
100-120	-	-	-	33	-	-
140-160	-	-	-	25	-	-

Profile description

Ap 0-18 cm	(7.5YR 2.5/2, dry) very dark brown (7.5YR 2/2, moist)sandy clay loam,very weak fine and medium subangular blocky and weak fine platy,slightly hard friable slightly sticky slightly plastic,highly porous (>60 vol%),common fine roots,non calcareous,clear smooth boundary to,
Ah1 18-40 cm	dark reddish brown (5YR 3/3, dry) (7.5YR 2/3, moist)sandy clay loam,moderate very fine and fine subangular blocky,slightly hard very friable slightly sticky slightly plastic,highly porous (>60 vol%),few fine roots,non calcareous,clear smooth boundary to,
Ah2 40-70 cm	dark reddish brown (5YR 3/3, dry) (7.5YR 2/3, moist)sandy clay,weak medium subangular blocky,slightly hard very friable slightly sticky slightly plastic,highly porous (>60 vol%),few fine roots,non calcareous,gradual smooth boundary to,
Ah3 70-90 cm	dark reddish brown (5YR 3/3, dry) (7.5YR 2/3, moist)sandy clay,weak to moderate fine subangular blocky,slightly hard very friable slightly sticky slightly plastic,highly porous (>60 vol%),few fine roots,non calcareous,gradual smooth boundary to,
ABh 90-105 cm	(5YR 3/6, dry) (5YR 2/4, moist)clay,weak medium subangular blocky,slightly hard very friable slightly sticky slightly plastic,common (5-15%) coarse distinct clear mottles,highly porous (>60 vol%),few fine roots,non calcareous,gradual smooth boundary to,
Bt1 105-150 cm	red (2.5YR 4/8, dry) (2.5YR 3/8, moist)clay,very weak very coarse subangular blocky parting to weak medium subangular blocky,slightly hard very friable slightly sticky slightly plastic,highly porous (>60 vol%),non calcareous,gradual smooth boundary to,
Bt2 150-180 cm	red (10R 4/8, dry)slightly gravelly clay loam,very weak very coarse subangular blocky parting to weak medium subangular blocky,few weathered sandstone,non calcareous,

Kind 1 (parent material) ; Parker (eds), 1984	sandstone
Mode of accumulation or deposition of parent material	residual material
Remarks on Parent Materials	Weathered material derived from arkosic sandstone of the Table Mountain Series
Texture of parent material	clayey
Texture of parent material (second entry)	clayey
Weathering Resistance	moderate
General characterization of the status of weathering of solid rock	highly

Major crops	sugar cane
Land use or vegetation in the immediate vicinity of the site	arable farming

Altitude	1000m
Physiographic Unit	gently undulating Late Tertiary plateau
Physiographic position of the site	slope
Regional landform; McDonald, R.C., Isbell, R.F. et all, 1984; Australian soil and land survey Field Handbook, Inkata Press, Melbourne.	plateau
Slope	4%
Slope Aspect	south-west
Form of the slope surrounding the site	concave
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)	medium

Evidence of alkali ; Soil Survey Manual USDA, 1951	non-alkaline
Surface cracking	small cracks (width less than 1 cm, or depth less than 50 cm)
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 South Africa 21: Alisol

Characteristics

Reference soil ZA021: Alisols

Classification