Reference soil Rwanda 09: Nitisol

RW009

Distribution of Nitisols (rough estimation supplied by soilgrids)

Ap: Upper part of the horizon shows tendency for slight massive structure. AB: Common discontinuous distinct thin dark reddisch brown (5YR 3/2) skeletans over argillans on vertical and horizontal ped faces. Coarse termite holes are filled with organic clayey material. Soft iron concretions color is reddish brown (5YR 4/4). Bt: Many discontinuous distinct thin dark brown (7.5YR 3/4) skeletans over argillans on vertical and horizontal ped faces. Coarse ant and termite channels filled with organic dark reddish brown (5YR 3/2) clayey material. Coarse sand grains are cloudy and subrounded. Bth1: Common discontinuous distinct thin dark reddish brown (5YR 2/2) skeletans over argillans on vertical and horizontal ped faces. Few to common, fine to coarse, divided to powdery charcoal in soft dark concretions. Soft iron concretion seems to be of iron oxide or saprolite bodies. Bth2: Common discontinuous distinct thin skeletans over argillans on vertical and horizontal ped faces. Soft dark concretion seems to be biological. 2Bsc: Many discontinuous distinct thin yellowish red (5YR 5/6) non specific pressure faces on sand and gravel. Termite channels filled with humic clayey material transversed by roots. Coarse round ironstone nodules seems to be petroplinthic nodules with 3 shapes, inside colour very dark greyish brown (10YR 3/2) and (dark) yellowish brown (10YR 3/6). Slides: 9969 - 9974.

Classification

WRB 2006
Umbric-Ferralic Nitisol (Sombric Humic Alumic Clayic)
0-50 cm	umbric horizon
50-160 cm	nitic horizon
160-185 cm	argic horizon
-	ferralic
FAO-UNESCO-ISRIC 1988		FAO-UNESCO-ISRIC 1974
Alumi-Humic Cambisol		Humic Cambisol
0-50 cm	ochric A horizon	0-50 cm	ochric A horizon
50-160 cm	cambic B horizon	50-160 cm	cambic B horizon
160-185 cm	argic B horizon	160-185 cm	argillic B horizon

Classification information

Kabira Series

Other classification

USDA-SCS (1975)

Sombrihumult udic clayey kaolinitic isothermic

Location:

Préfecture Rutare, commune Kabiro, secteur Gashinya

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Physical characteristics

Particle size distribution

Depth (cm)	coarse sand % w/w	very coarse sand % w/w	Gravel % v/v	Total silt % w/w	medium sand % w/w	fine silt % w/w	fine sand % w/w	Clay % w/w	Total sand % w/w	coarse silt % w/w	very fine sand % w/w
0-30	5.6	2.1	0	25.3	13.7	17.0	10.8	18.6	36.1	8.3	3.9
30-50	6.3	1.7	0	24.2	14.2	16.2	10.5	19.4	36.4	8.0	3.7
50-101	5.5	1.3	0	22.6	13.0	15.1	9.7	44.5	32.9	7.5	3.4
101-140	6.7	2.5	0	22.8	15.2	14.8	10.6	38.5	38.7	8.0	3.7
140-160	6.1	3.5	1	21.1	13.8	14.9	9.9	42.1	36.8	6.2	3.5
160-185	5.3	5.4	60	12.5	8.3	8.9	5.7	60.4	27.1	3.6	2.4

Water retention characteristics

Depth (cm)	pF 4.2 % v/v	pF 1.0 % v/v	pF 1.5 % v/v	pF 2.7 % v/v	pF 2.0 % v/v	pF 3.4 % v/v	Bulk density kg/dm³	pF 2.3 % v/v	pF 0 % v/v
0-30	19.4	-	-	-	-	-	1.36	-	-
30-50	14.2	-	-	-	-	-	1.43	-	-
50-101	14.1	-	-	-	-	-	1.50	-	-
101-140	12.5	-	-	-	-	-	1.44	-	-
140-160	14.0	-	-	-	-	-	1.51	-	-
160-185	18.2	-	-	-	-	-	1.50	-	-

Other physical data

Depth (cm)	Spec. Surf. Area m²/g	Water disp. clay %	Clay % w/w	Bulk density kg/dm³	COLE cm/cm
0-30	-	-	18.6	1.36	0.031
30-50	-	-	19.4	1.43	0.022
50-101	-	-	44.5	1.50	0.021
101-140	-	-	38.5	1.44	0.017
140-160	-	-	42.1	1.51	0.014
160-185	-	-	60.4	1.50	0.009

Chemical data

Depth (cm)	pHKCl unitless	Exch. Acid cmol(c)/kg	Na cmol(c)/kg	Sum Cations cmol(c)/kg	Ca cmol(c)/kg	EC 1: 2.5 mS/cm	K cmol(c)/kg	Mg cmol(c)/kg	pH H2O unitless	C / N unitless	Exch. Al cmol(c)/kg	N %	C % w/w	CaCO3 % w/w
0-30	4.3	22.3	0.1	9.9	7.8	-	0.1	1.9	5.2	13	0.5	0.27	3.46	-
30-50	4.2	16.1	0.1	7.7	6.5	-	0.0	1.1	5.3	12	0.7	0.16	1.98	-
50-101	4.0	11.8	0.1	4.4	3.3	-	0.0	1.0	5.2	8	0.7	0.11	0.91	-
101-140	3.7	13.4	0.1	2.5	1.8	-	0.1	0.5	5.0	11	1.8	0.08	0.86	-
140-160	3.6	13.4	0.0	1.4	1.1	-	0.0	0.3	4.9	10	2.3	0.07	0.71	-
160-185	3.6	13.8	0.1	1.1	0.8	-	0.0	0.2	4.7	8	2.5	0.07	0.57	-

Depth (cm)	Al sat. %	ESP %	Base sat. %	CEC soil cmol(c)/kg	ECEC cmol(c)/kg	CEC clay cmol(c)/kg	CEC org cmol(c)/kg
0-30	2	0	40	24.7	32.2	64	12.1
30-50	4	1	46	16.9	23.8	43	6.9
50-101	7	1	42	10.4	16.2	23	3.2
101-140	18	1	26	9.8	15.9	25	3.0
140-160	25	0	15	9.2	14.8	22	2.5
160-185	26	1	12	9.5	14.9	16	2.0

Depth (cm)	pH NaF unitless	P Retention %	Si o % w/w	Al d % w/w	Fe o % w/w	Al p % w/w	Al o % w/w	ODOE unitless	C p % w/w	Fe p % w/w	Fe d % w/w
0-30	8.8	59	0.0	0.7	0.6	0.3	0.3	-	-	0.6	3.9
30-50	9.0	55	0.0	0.6	0.6	0.2	0.3	-	-	0.5	4.0
50-101	9.1	54	0.0	0.6	0.7	0.2	0.2	-	-	0.8	4.5
101-140	9.1	52	0.0	0.6	0.6	0.2	0.2	-	-	1.0	4.7
140-160	9.1	50	0.0	0.7	0.6	0.3	0.2	-	-	1.3	5.0
160-185	9.1	59	0.0	1.0	0.5	0.3	0.2	-	-	1.6	7.8

Depth (cm)	CaSO4.2H2O %	P Bray mg/kg	P Olsen mg/kg	pH CaCl2 unitless
0-30	-	-	-	4.5
30-50	-	-	-	4.6
50-101	-	-	-	4.4
101-140	-	-	-	4.1
140-160	-	-	-	4.0
160-185	-	-	-	4.0

Clay mineralogy

Depth (cm)	Mixed-layer unitless	Chlorite unitless	Mica / illite unitless	Kaolinite unitless	Hematite unitless	Feldspar unitless	Vermiculite unitless	Gibbsite unitless	Halloysite unitless	Smec unitless	Quartz unitless	Goethite unitless
50-101	-	-	weak	very strong	-	-	-	-	-	very weak to weak	-	very weak to weak
140-160	-	-	weak	very strong	-	-	-	-	-	-	-	weak

Profile description

Ap 0-30 cm	(5YR 2/2, moist)clay,moderate coarse subangular blocky parting to moderate coarse crumb,slightly hard firm slightly sticky plastic,common to many fine to coarse vesicular pores and common fine to coarse tubular pores,many fine and medium and common coarse roots,non calcareous,clear smooth boundary to,
A/B 30-50 cm	dark reddish brown (5YR 3/3, moist)clay,moderate coarse subangular blocky,firm slightly sticky plastic,patchy thin clay cutans on horizontal and vertical pedfaces,common fine to coarse vesicular and tubular pores,common very fine and fine and common medium roots,few large spherical soft ferruginous concretions very few large spherical hard ferruginous nodules,termite channels,non calcareous,clear smooth boundary to,
Bt 50-101 cm	reddish brown (5YR 4/4, moist)clay,moderate to strong very coarse subangular blocky,hard firm slightly sticky plastic,broken thin clay cutans on horizontal and vertical pedfaces,common fine to coarse vesicular and tubular pores,common very fine and fine roots,very few large spherical hard ferruginous nodules,termite channels,non calcareous,gradual wavy boundary to,
Bth1 101-140 cm	dark reddish brown (5YR 3/4, moist)clay,moderate coarse subangular blocky,firm slightly sticky plastic,broken thin clay cutans on horizontal and vertical pedfaces,common fine to coarse vesicular and tubular pores,few very fine and fine roots,very few large irregular soft ferruginous concretions few charcoal,few fine gravel charcoal conc. fragments,non calcareous,gradual wavy boundary to,
Bth2 140-160 cm	reddish brown (5YR 4/4, moist)clay,moderate coarse subangular blocky,slightly hard friable sticky plastic,patchy thin unspecified cutans on horizontal and vertical pedfaces,common fine to coarse vesicular and tubular pores,few very fine and fine roots,few large irregular soft ferruginous concretions few charcoal,few coarse gravel charcoal conc. fragments,non calcareous,abrupt smooth boundary to,
Boc 160-185 cm	yellowish red (5YR 5/8, moist) and (5YR 5/6,moist)very gravelly clay,moderate coarse subangular blocky,hard firm slightly sticky plastic,many mottles (5 YR 5/6),broken thin pressure cutans around sand grains,common micro to medium vesicular and tubular pores,few very fine and fine roots,frequent large spherical hard ferruginous nodules,many medium gravel Fecoated rock,termite channels,non calcareous,

Kind 1 (parent material) ; Parker (eds), 1984	schist
Kind 2 (parent material) (second entry); Parker (eds), 1984	metamorphic/sedimentary rock
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	schist & thyllite
Soil Depth	160cm
Texture of parent material	clayey
Texture of parent material (second entry)	clayey
Weathering Resistance	moderate
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

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

Major crops	maize
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	fallow
Remarks on Land Use / Vegetation	LAND USE: agricultural research station
Rotation scheme ; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	crop with current fallow

Altitude	2018m
Physiographic Unit	hillside in high hills
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	5%
Slope Aspect	east
Form of the slope surrounding the site	concave
Topography; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	hilly

Drainage class ; FAO (2006) - Guidelines for soil description	very poor
Flooding frequency (FAO, 1986)	never
Kind of ground water table (USDA, 1979)	no groundwater table observed
Moist From - To	0-185cm
Estimated permeability (class) of least permeable part of the profile	moderate
Estimated run off (class)	medium
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

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Reference soil Rwanda 09: Nitisol

Classification