Reference soil Kenya 16: Nitisol

KE016

Nitisols occur mainly in the tropics and subtropics, as well as in areas with a Mediterranean type of climate. They are associated with basic rocks (e.g. basalts) or hard limestone or dolomite deposits.

Characteristics

Soils having a nitic horizon (a horizon with pronounced nut-shaped soil structure and significant amount of active iron) within 100 cm from the soil surface, and gradual to diffuse horizon boundaries between the surface and the underlying horizons. They do not have a ferric, plinthic or vertic horizon within 100 cm from the soil surface.

Distribution of Nitisols (rough estimation supplied by soilgrids)

Reference soil KE016: Nitisols

A porous, deep-rooting clayey soil in forestal upland, of volcanic origin (trachytes), with 40 % trees, 20 % shrubs, and 40 % herbs. Below 10 cm clay cutans appear increasing with depth; soft sesquioxidic accumulations in Bt2 horizon. In the Bt1 horizon there are some charcoal fragments; partly consolidated ash is observed at one side of the soil pit at 71 cm depth.

Classification

WRB 2006

WRB 1998

Lixic-Ferralic- Nitisol (Humic Eutric Clayic)

Rhodi-Humic- Nitisol (Eutric)

35-150 cm	nitic horizon
-	ferralic

FAO-UNESCO-ISRIC 1988

FAO-UNESCO-ISRIC 1974

Humi-Rhodic Nitisol

Ferric Luvisol

0-35 cm	ochric A horizon
10-150 cm	argic B horizon
-	nitic
-	strongly humic

0-35 cm	ochric A horizon
10-150 cm	argillic B horizon
-	ferric

Other classification

USDA-NRCS (1999)	Rhodic Kandiustalf
USDA-SCS (1975)	Rhodic Paleustalf ustic 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
0-10	-	0.2	0.7	1.3	2.3	1.3	5.8	2.9	16.4	19.3	74.8
10-35	-	0.2	0.6	1.0	1.8	1.2	4.8	1.2	14.3	15.5	79.6
35-80	-	0.1	0.3	0.8	1.3	0.9	3.4	0.3	12.7	13	83.7
80-120	-	0.1	0.2	0.3	0.5	0.3	1.4	0.6	7.6	8.2	90.3

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	-	-	-	15.5	74.8
10-35	-	-	-	9.0	79.6
35-80	-	-	-	4.5	83.7
80-120	-	-	-	1.0	90.3

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	6.4	5.4	0.28	-	6.54	0.55	12	8.9	0.0	12.8	8.1	2.9	0.0	23.8
10-35	5.7	4.0	0.16	-	2.91	0.28	10	13.6	0.3	3.2	2.8	2.3	0.1	8.4
35-80	5.8	4.3	0.08	-	0.96	0.14	7	9.4	0.1	4.0	3.3	1.0	0.1	8.4
80-120	5.4	4.0	0.07	-	0.34	0.06	6	9.1	0.5	2.4	3.1	0.8	0.0	6.3

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	77	30.9	41	22.9	-	-	0
10-35	44	19.2	24	10.2	-	-	1
35-80	57	14.7	18	3.4	-	-	1
80-120	52	12.2	14	1.2	-	-	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	-	-	-	0.23	-	7.48	0.47	0.13	0.07	-	0.60
10-35	-	-	-	0.26	-	7.90	0.57	0.26	0.19	-	0.64
35-80	-	-	-	0.22	-	7.68	0.55	0.09	0.29	-	0.54
80-120	-	-	-	0.09	-	8.05	0.28	0.03	0.14	-	0.17

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
0-10	39.1	28.9	16.5	0.15	0.22	0.54	-	1.62
10-35	40.2	30.4	16.3	0.02	0.19	0.51	-	1.56
35-80	38.5	29.9	15.3	0.03	0.19	0.43	-	1.42
80-120	39.5	31.6	14.6	0.01	0.18	0.29	-	1.37

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
0-10	0.18	0.28	12.7	100.19	2.3	6.3	1.7	2.7
10-35	0.23	0.19	12.3	101.9	2.2	6.6	1.7	2.9
35-80	0.21	0.12	12.3	98.4	2.2	6.7	1.6	3.1
80-120	0.13	0.11	12.4	100.19	2.1	7.2	1.6	3.4

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
0-10	22.2	0.64	13.1	1.20	0.36	-	41.1	1.44
10-35	24.5	0.17	14.2	1.09	0.23	-	41.1	1.51
35-80	26.5	0.15	14.3	0.88	0.21	-	41.7	1.50
80-120	30.0	0.06	14.8	0.43	0.19	-	40.1	1.56

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
0-10	2.7	19.8	0.57	0.18	3.1	8.4	2.3
10-35	2.7	14.7	0.52	0.11	2.8	7.7	2.1
35-80	2.9	12.3	0.33	0.07	2.7	7.8	2
80-120	3.2	12.5	0.15	0.06	2.3	7.2	1.7

Clay mineralogy

Depth (cm)	Chlorite	Feldspar	Gibbsite	Goethite	Halloysite	Hematite	Kaolinite	Mica / illite	Mixed-layer	Quartz	Smec	Vermiculite
0-10	-	weak to medium	-	weak to medium	-	-	strong	weak	-	-	-	-
10-35	-	weak to medium	-	weak to medium	-	-	strong	weak	-	-	-	-
35-80	-	weak	-	weak to medium	-	-	strong	very weak to weak	-	-	-	-
80-120	-	-	-	weak to medium	-	-	very strong	very weak to weak	-	-	-	-

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
0-10	4.5	88	95.5	96	1	11
10-35	5.4	86	94.6	98	3	11
35-80	4.7	91	95.3	94	-	9
80-120	9.2	93	90.8	97	-	7

Minerals

Depth (cm)	Anatase % w/w	Andalusite % w/w	Apatite % w/w	Augite % w/w	Biotite % w/w	Hornblende (basaltic) % w/w
0-10	-	-	-	-	-	46
10-35	-	-	-	-	-	47
35-80	-	-	-	-	-	42
80-120	-	-	-	-	-	4

Depth (cm)	Brookite % w/w	Chloritic % w/w	Disthene % w/w	Epidote % w/w	Garnet % w/w	Glaucophane % w/w
0-10	-	-	-	1	-	-
10-35	-	-	-	6	-	-
35-80	-	-	-	1	-	-
80-120	-	-	1	-	-	-

Depth (cm)	Grenate % w/w	Grossular % w/w	Muscovite % w/w	Rutile % w/w	Sillimanite % w/w	Spinel % w/w
0-10	2	-	-	6	-	-
10-35	-	-	-	4	1	-
35-80	-	-	-	2	1	-
80-120	1	-	-	2	-	-

Profile description

A 0-10 cm	dark reddish brown (5YR 3/2, dry) dark reddish brown (2.5YR 2.5/4, moist)clay loam,very fine and fine crumb,very friable slightly sticky slightly plastic,many fine pores and common medium pores,non calcareous,clear smooth boundary to,
10-35 cm	dark reddish brown (2.5YR 3/4, moist)clay,moderate fine and medium subangular blocky and moderate coarse subangular blocky,very friable sticky plastic,patchy thin clay cutans,many fine pores and common medium pores,very few charcoal fragments,non calcareous,gradual wavy boundary to,
Bt1 35-100 cm	dark reddish brown (5YR 3/3, dry) dark brown (10YR 3/3, moist)clay,moderate medium angular blocky,very friable sticky plastic,broken thick clay cutans,many fine pores and common medium pores,non calcareous,gradual smooth boundary to,
Bt2 100-150 cm	dark yellowish brown (10YR 3/6, moist)clay,strong medium and coarse angular blocky,friable sticky plastic,broken thick clay on pedfaces cutans,many fine pores and common medium pores,very few small soft ferruginous concretions and very few soft manganiferous concretions,non calcareous,

Kind 1 (parent material) ; Parker (eds), 1984	fine-grained igneous rock
Mode of accumulation or deposition of parent material	residual material
Remarks on Parent Materials	Tertiary Limuru trachyte
Texture of parent material	clayey
Weathering Resistance	moderate
General characterization of the status of weathering of solid rock	highly

Land use or vegetation in the immediate vicinity of the site	reserves
Remarks on Land Use / Vegetation	VEGETATION: 40% trees (mainly Mutamau), 20% shrubs (mainly Mugaita) and 40% herbs. LAND USE: USed for charcoal production
Major vegetation type; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	woodland

Altitude	2170m
Physiographic Unit	volcanic upland
Physiographic position of the site	middle slope
Regional landform; McDonald, R.C., Isbell, R.F. et all, 1984; Australian soil and land survey Field Handbook, Inkata Press, Melbourne.	plain
Slope	2%
Topography; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	rolling

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	slow
Estimated run off (class)	slow

Evidence of alkali ; Soil Survey Manual USDA, 1951	non-alkaline
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 Kenya 16: Nitisol

Characteristics

Reference soil KE016: Nitisols

Classification