Reference soil Rwanda 07: Ferralsol

RW007

Ferralsols occur in tropical and subtropical regions of the world, mainly on old and stable land surfaces.

Characteristics

Soils having a ferralic horizon (strongly weathered horizon with low-activity clays and very low amounts of weatherable minerals) between 25 and 200 cm from the soil surface. They lack a nitic horizon (a horizon with strongly developed, nut-shaped structure) and do not have a layer which fulfils the requirements of an argic horizon and which has, in the upper 30 cm, 10 percent or more water-dispersible clay.

Distribution of Ferralsols (rough estimation supplied by soilgrids)

Reference soil RW007: Ferralsols

Crops: Bananas, cowpeas, maize and cassava are grown. Vegetation: grssland with some Digitaria sp., Brachyaria sp., Monechma subsessile. Physiography: Hilly landscape with large plateaus on which ironstone occurs, large valleys with hydromorphic soils sometimes peaty, average difference between hilltops and valley bottoms is 80m. The soil profile: A: many chitinous grains of biologic origin. Bu1: some charcoal. 2B: some hardened angular and subangular blocks of variable size, very dusky red (4YR2/2). 3C: presence of many hardened blocks of 2.5YR3/6; many coatings. Slides: 9952 - 9960.

Classification

WRB 2006

Haplic- Ferralsol (Sombric Humic Alumic Clayic)

0-108 cm

ferralic horizon

0-108 cm

ferralic horizon

FAO-UNESCO-ISRIC 1988

FAO-UNESCO-ISRIC 1974

Humi-Rhodic Ferralsol

Humic Ferralsol

0-25 cm	ochric A horizon
25-108 cm	ferralic B horizon
-	strongly humic

0-25 cm	ochric A horizon
25-108 cm	oxic B horizon
-	high organic matter content in B horizon

Local classification:	Ferralsol/Ferrisol (INEAC)

Other classification

USDA-SCS (1975)

Sombrihumult udic fine kaolinitic isothermic

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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
0-25	0	2.7	7.6	12.0	12.0	4.1	38.4	3.0	6.8	9.8	51.8
25-60	0	4.5	7.9	10.5	11.7	4.1	38.7	3.6	5.9	9.5	51.8
60-86	0	3.3	9.2	9.2	10.3	4.1	36.1	3.1	5.4	8.5	55.4
86-108	0	4.8	7.1	8.8	9.8	4.0	34.5	3.1	5.9	9	56.5
108-137	0	6.1	5.7	7.7	9.2	3.5	32.2	3.2	4.2	7.4	60.4
137-175	0	5.5	4.6	6.7	7.4	2.7	26.9	1.3	5.0	6.3	66.8

Water retention characteristics

Depth (cm)	Bulk density kg/dm³	Spec. Surf. Area m²/g	COLE cm/cm	Water disp. clay %	Clay % w/w
0-25	-	101	-	-	51.8
25-60	-	94	-	-	51.8
60-86	-	101	-	-	55.4
86-108	-	108	-	-	56.5
108-137	-	111	-	-	60.4
137-175	-	111	-	-	66.8

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
0-25	-	-	-	-	-	-	-	-	15.6
25-60	-	-	-	-	-	-	-	-	14.9
60-86	-	-	-	-	-	-	-	-	15.3
86-108	-	-	-	-	-	-	-	-	16.1
108-137	-	-	-	-	-	-	-	-	16.8
137-175	-	-	-	-	-	-	-	-	19.5

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
0-25	4.8	3.8	-	-	2.24	0.18	12	16.7	4.0	0.4	0.1	0.1	0.1	0.7
25-60	4.8	3.4	-	-	1.58	0.11	14	15.5	3.8	0.4	0.0	0.0	0.0	0.4
60-86	4.9	3.8	-	-	1.05	0.10	11	12.7	2.8	1.9	0.0	0.0	0.0	1.9
86-108	4.8	3.8	-	-	1.17	0.10	12	12.9	2.1	3.9	0.1	0.0	0.0	4
108-137	5.1	3.9	-	-	1.27	0.09	14	13.5	1.9	4.6	0.1	0.0	0.0	4.7
137-175	5.1	3.9	-	-	0.68	0.06	11	10.1	1.5	3.8	0.2	0.0	0.0	4

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 %
0-25	6	12.4	24	7.8	17.4	32	1
25-60	4	11.3	22	5.5	15.9	34	0
60-86	17	11.0	20	3.7	14.6	25	0
86-108	31	12.7	22	4.1	16.9	17	0
108-137	32	14.6	24	4.4	18.2	13	0
137-175	38	10.4	16	2.4	14.1	14	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
0-25	8.6	-	0.12	0.26	-	3.4	0.6	-	-	-	0.40
25-60	9.2	-	0.09	0.26	-	3.3	0.6	-	-	-	0.29
60-86	9.1	-	0.07	0.20	-	3.6	0.5	-	-	-	0.30
86-108	8.8	-	0.08	0.20	-	3.7	0.6	-	-	-	0.22
108-137	9.0	-	0.07	0.19	-	3.9	0.6	-	-	-	0.20
137-175	8.9	-	0.05	0.14	-	4.1	0.7	-	-	-	0.14

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
0-25	-	-	-	4.0	-	-	-	-	-
25-60	-	-	-	4.1	-	-	-	-	-
60-86	-	-	-	4.2	-	-	-	-	-
86-108	-	-	-	4.3	-	-	-	-	-
108-137	-	-	-	4.3	-	-	-	-	-
137-175	-	-	-	4.4	-	-	-	-	-

Clay mineralogy

Depth (cm)	Chlorite	Feldspar	Gibbsite	Goethite	Halloysite	Hematite	Kaolinite	Mica / illite	Mixed-layer	Quartz	Smec	Vermiculite
25-60	very weak to weak	-	-	very weak to weak	-	-	strong	-	-	-	-	-
137-175	weak	-	-	-	-	-	very strong	weak	-	-	-	-

Profile description

Ah 0-25 cm	dark reddish brown (5YR 3/4, moist)clay,weak medium crumb,friable,patchy thin clay cutans,many fine roots,few large irregular hard ferruginous segregations,non calcareous,gradual smooth boundary to,
Bw1 25-60 cm	Invalid Code: (5YR 3/6, moist)clay,moderate medium angular blocky and moderate medium subangular blocky,friable,patchy thin clay cutans,many fine roots,few charcoal,non calcareous,clear irregular boundary to,
Bw2 60-86 cm	(5YR 3/6, moist)clay,moderate medium angular blocky and moderate medium subangular blocky,friable,patchy thin clay cutans,many fine roots,few charcoal,non calcareous,clear irregular boundary to,
2Bw3 86-108 cm	dark reddish brown (5YR 3/3, moist)clay,weak fine subangular blocky and weak medium subangular blocky,friable,many fine roots,few large irregular hard ferruginous segregations,non calcareous,gradual irregular boundary to,
3A 108-137 cm	(5YR 2.5/3, moist)clay,moderate fine angular blocky and moderate medium angular blocky,firm,common fine roots,few charcoal,non calcareous,gradual irregular boundary to,
3C 137-175 cm	(2.5YR 3/3, moist)clay,strong fine angular blocky and strong medium angular blocky,very firm,common (5-15%) mottles (4 YR 5/3),continuous clay cutans,few fine roots,frequent large irregular soft ferruginous segregations,non calcareous,gradual smooth boundary to,

Kind 1 (parent material) ; Parker (eds), 1984	granite
Mode of accumulation or deposition of parent material	residual material
Remarks on Parent Materials	graniste associated with migmatite and shales
Soil Depth	175cm
Texture of parent material	clayey
Weathering Resistance	high
General characterization of the status of weathering of solid rock	highly

Occurrence of soil aggradation (McDonald et al., 1984)	absent
Slope stability	stable

Land improvements ; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	terracing
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	woodland, grazed
Remarks on Land Use / Vegetation	VEGETATION: Grassland with some Eucalyptus sp., Digitaria sp., Brachyaria sp. and Monechma subsessile. LAND USE: Crops: bananas, cowpeas, maize and cassave
Rotation scheme ; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	continuous crop rotation
Major vegetation type; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	grassland

Altitude	1710m
Physiographic Unit	slope to plateau
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.	plateau
Slope	20%
Slope Aspect	west
Form of the slope surrounding the site	convex
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
Moist From - To	0-180cm
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	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

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Reference soil Rwanda 07: Ferralsol

Characteristics

Reference soil RW007: Ferralsols

Classification