Reference soil Rwanda 02: Andosol

RW002

Andosols occur throughout the world where volcanic activity is common, especially in the circum-Pacific region and along the mid-Atlantic Ridge.

Characteristics

Soils with a vitric or andic horizon (slightly to moderately weathered horizons in pyroclastic deposits dominated by short-range-order minerals, notably allophane and imogolite) starting within 25 cm from the soil surface. In addition, they may have a histic, fulvic, melanic, mollic, umbric, ochric, duric, or cambic horizon. Other diagnostic horizons (unless buried deeper than 50 cm by volcanic deposits) are absent.

Distribution of Andosols (rough estimation supplied by soilgrids)

Reference soil RW002: Andosols

LOCATION: sous prefecture Mutura, commune Kora, secteur Kijote. PROFILE DESCRIPTION: Ah1, Ah2, Bw1, Bw2 and B/C may be thixotropic. Ah1, Ah2, Bw1 and Bw2: coatings on peds may be clay films and range in colour from 10YR 2/1 (Ah1) to 10YR 3/2 (Bw2). The other matrix colours of the 3C2 horizon are described in "mottles". Other dry colours 3C2 horizon: yellowish brown (10YR5/6) and dark yellowish brown (10YR 4/4). SLIDES: 9922 - 9926 and 9987 - 9990.

Classification

WRB 2006

Mollic-Silandic-Vitric- Andosol (Eutric Thixotropic Siltic)

35-115 cm	cambic horizon
-	andic
-	vitric

35-115 cm	cambic horizon
-	andic
-	vitric

FAO-UNESCO-ISRIC 1988

FAO-UNESCO-ISRIC 1974

Humi-Mollic Andosol

Mollic Andosol

0-35 cm	mollic A horizon
35-115 cm	cambic B horizon
-	andic
-	strongly humic

0-35 cm	mollic A horizon
35-115 cm	cambic B horizon
-	exchange complex dominated by amorphous material

Local classification:	Bigogwe Series

Other classification

USDA-NRCS (1999)	Typic Melanudand
USDA-SCS (1975)	Typic Eutrandept udic medial isothermic

More images

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	2.5	2.4	2.7	5.8	4.2	17.6	10.3	47.3	57.6	24.8
10-35	0	0.4	1.9	3.0	5.8	8.6	19.7	19.2	50.5	69.7	10.6
35-95	0	0.9	2.1	2.4	8.5	25.5	39.4	22.8	32.9	55.7	4.9
95-115	4	4.4	3.2	3.7	16.0	27.3	54.6	18.9	23.0	41.9	3.5
115-140	24	16.9	8.2	6.4	13.0	13.1	57.6	14.7	23.0	37.7	4.7
140-152	16	8.7	7.4	10.1	21.2	16.7	64.1	13.2	20.4	33.6	2.3
152-195	0	15.7	12.4	11.8	20.8	17.3	78	11.2	9.2	20.4	1.6

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	0.96	-	0.111	-	24.8
10-35	1.06	-	0.089	-	10.6
35-95	0.98	-	0.088	-	4.9
95-115	0.94	-	0.082	-	3.5
115-140	-	-	-	-	4.7
140-152	-	-	-	-	2.3
152-195	-	-	-	-	1.6

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
0-10	0.96	-	-	-	-	-	79.0	-	55.7
10-35	1.06	-	-	-	-	-	60.0	-	35.5
35-95	0.98	-	-	-	-	-	57.1	-	32.5
95-115	0.94	-	-	-	-	-	56.4	-	29.6

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	7.0	6.0	-	0	8.57	0.97	9	-	-	52.6	14.3	6.6	0.2	73.7
10-35	7.1	6.1	-	0	4.02	0.47	9	-	-	28.3	9.9	4.8	0.2	43.2
35-95	7.0	6.0	-	0	3.02	0.34	9	-	-	23.0	10.0	5.6	0.1	38.7
95-115	7.0	5.8	-	0	2.41	-	-	-	-	22.5	8.8	6.5	0.0	37.8
115-140	7.2	6.0	-	0	1.79	-	-	-	-	20.6	8.2	6.9	0.1	35.8
140-152	7.3	5.9	-	0	1.30	-	-	-	-	22.3	9.5	6.8	0.1	38.7
152-195	7.8	6.6	-	0	0.32	-	-	-	-	11.1	4.4	2.9	0.3	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	103	71.7	168	30	-	-	0
10-35	89	48.3	323	14	-	-	0
35-95	88	43.8	677	11	-	-	0
95-115	85	44.7	-	8	-	-	0
115-140	83	43.1	783	6	-	-	0
140-152	87	44.7	-	5	-	-	0
152-195	98	19.0	-	1	-	-	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
0-10	9.1	65	-	0.6	0.4	3.7	0.5	0.7	0.2	-	1.8
10-35	9.4	68	-	0.7	0.4	4.5	0.6	0.4	0.0	-	1.7
35-95	9.5	75	-	0.7	0.4	4.5	0.6	0.3	0.2	-	1.7
95-115	9.7	87	-	1.2	0.3	5.7	0.9	0.5	0.3	-	2.6
115-140	9.7	82	-	0.9	0.6	3.9	0.6	0.3	0.3	-	2.1
140-152	9.8	89	-	1	0.8	4.8	0.6	0.2	0.2	-	2.5
152-195	9.5	33	-	0.6	0.7	1.1	0.2	0.1	0.1	-	1.3

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	-	-	-	6.4	-	-	-	-	-
10-35	-	-	-	6.5	-	-	-	-	-
35-95	-	-	-	6.4	-	-	-	-	-
95-115	-	-	-	6.4	-	-	-	-	-
115-140	-	-	-	6.4	-	-	-	-	-
140-152	-	-	-	6.5	-	-	-	-	-
152-195	-	-	-	7.1	-	-	-	-	-

Clay mineralogy

Depth (cm)	Chlorite	Feldspar	Gibbsite	Goethite	Halloysite	Hematite	Kaolinite	Mica / illite	Mixed-layer	Quartz	Smec	Vermiculite
10-35	-	-	-	-	very weak	-	-	very weak	-	-	-	very weak
95-115	-	-	-	-	very weak	-	-	very weak	-	-	-	very weak

Profile description

Ah1 0-10 cm	very dark brown (10YR 2/2, moist)silt loam,moderate fine and medium subangular blocky parting to moderate medium and coarse crumb,firm non sticky non plastic,broken thin humus cutans on horizontal and vertical pedfaces,common fine vesicular pores and common fine tubular pores highly porous (>60 vol%),many fine and medium and many coarse roots,non calcareous,clear wavy boundary to,
Ah2 10-35 cm	dark brown (10YR 3/3, dry) very dark brown (10YR 2/2, moist)silt loam,moderate fine and medium subangular blocky,firm non sticky non plastic,continuous thin clay and humus cutans on horizontal and vertical pedfaces,common fine and medium vesicular pores and common fine and medium tubular pores highly porous (>60 vol%),many fine and medium and many coarse roots,non calcareous,diffuse smooth boundary to,
2Bw1 35-95 cm	dark yellowish brown (10YR 3/4, dry) very dark brown (7.5YR 2/2, moist)silt loam,moderate fine and medium subangular blocky,slightly hard firm non sticky non plastic,broken thin clay and humus cutans on horizontal and vertical pedfaces,common fine and medium vesicular pores and common fine and medium tubular pores highly porous,common fine and medium and common coarse roots,non calcareous,clear irregular boundary to,
2Bw2 95-115 cm	dark yellowish brown (10YR 3/6, dry) dark yellowish brown (10YR 3/4, moist)silt loam,moderate fine and medium subangular blocky,slightly hard friable non sticky non plastic,patchy thin clay and humus cutans on horizontal and vertical pedfaces,common fine and medium vesicular pores and common fine and medium tubular pores highly porous,common fine and medium roots,common fine gravel weathered ejecta cinders fragments,non calcareous,clear wavy boundary to,
2B/3C 115-140 cm	dark yellowish brown (10YR 4/4, dry) very dark brown (10YR 2/2, moist)gravelly silt loam,massive parting to weak fine and medium granular,soft very friable non sticky non plastic,common very fine and fine vesicular pores and common very fine and fine tubular pores highly porous (>60 vol%),common very fine and fine roots,many gravel weathered ejecta cinders fragments,non calcareous,clear wavy boundary to,
3C1 140-152 cm	yellowish brown (10YR 5/6, dry) dark yellowish brown (10YR 3/6, moist)slightly gravelly silt loam,massive parting to weak fine and medium granular,soft very friable non sticky non plastic,common very fine and fine vesicular pores and common very fine and fine tubular pores highly porous (>60 vol%),few very fine and fine roots,common fine gravel weathered ejecta cinders fragments,non calcareous,abrupt wavy boundary to,
4C2 152-195 cm	very dark grey (10YR 3/1, dry) and (10YR 5/6, dry) and (10YR 4/4, dry), black (10YR 2/1, moist) and (10YR 4/4, moist) and ( 10YR 2/2, moist)gravel,massive and single grain,very hard extremely firm non sticky non plastic,many mottles (10YR 4/4) and many mottles (10YR 2/2),many fine to coarse vesicular pores highly porous (>60 vol%),few fine and medium roots,dominant weathered stratified cinders and ash,non calcareous,

Depth1	152cm
Kind 1 (parent material) ; Parker (eds), 1984	basic ash
Mode of accumulation or deposition of parent material	ejecta ash
Remarks on Parent Materials	eolian ejecta
Soil Depth	195cm
Texture of parent material	loamy
Weathering Resistance	poor
General characterization of the status of weathering of solid rock	highly

Occurrence of soil aggradation (McDonald et al., 1984)	absent
Intensity of the soil erosion type	slight
Soil erosion type	rill
Slope stability	stable

Land use or vegetation in the immediate vicinity of the site	natural forest and woodland
Remarks on Land Use / Vegetation	VEGETATION: ungrazed forest
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 forest

Altitude	2400m
Physiographic Unit	hillside in mountains
Physiographic position of the site	lower slope
Regional landform; McDonald, R.C., Isbell, R.F. et all, 1984; Australian soil and land survey Field Handbook, Inkata Press, Melbourne.	mountain
Slope	36%
Slope Aspect	north-west
Form of the slope surrounding the site	straight
Topography; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	steeply dissected

Drainage class ; FAO (2006) - Guidelines for soil description	very poor
Dry From - To	35-195cm
Flooding frequency (FAO, 1986)	never
Kind of ground water table (USDA, 1979)	no groundwater table observed
Moist From - To	0-35cm
Estimated permeability (class) of least permeable part of the profile	moderate
Estimated run off (class)	very rapid
Drainage class - intergrade; FAO (2006) - Guidelines for soil description	well

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 pattern	none
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

You are here

Reference soil Rwanda 02: Andosol

Characteristics

Reference soil RW002: Andosols

Classification