Reference soil Kenya 15: Nitisol

KE015

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 KE015: Nitisols

A porous, clayey soil under forest vegetation, derived from tertiary volcanics (trachytes), situated at a slope (0-2%) of 200m length; below 10cm clay cutans appear; below 35 cm few to many small sesquioxidic nodules appear increasing with depth.

Classification

WRB 2014

Nitisol

FAO-UNESCO-ISRIC 1988

FAO-UNESCO-ISRIC 1974

Rhodic Nitisol

Humic Nitosol

- cm	argic B horizon
- cm	ochric A horizon
-	nitic
-	strongly humic

- cm	ochric A horizon

Other classification

USDA-NRCS (1999)	Rhodic Paleustalf
USDA-SCS (1975)	Rhodic Paleustalf ustic clayey 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
0-3	-	0.3	1.5	2.2	2.6	1.6	8.2	5.5	21.4	26.9	64.9
3-13	-	0.7	1.7	2.5	3.2	1.9	10	8.3	36.0	44.3	45.7
13-33	-	0.5	1.4	2.4	3.2	2	9.5	5.6	34.9	40.5	50
33-65	-	0.8	1.8	2.9	3.7	2.3	11.5	11.3	29.5	40.8	47.8
65-89	-	0.6	1.4	2.4	3.2	1.9	9.5	6.2	21	27.2	63.4
89-113	-	0.7	1.2	2.3	3.2	1.8	9.2	6.2	20.6	26.8	64
113-153	-	2.4	4.1	3.7	4.3	2.4	16.9	8.8	21.3	30.1	53
153-213	-	0.2	0.7	1.3	1.9	1.2	5.3	2.2	11.3	13.5	81.5

Water retention characteristics

Depth (cm)	Bulk density kg/dm³	Spec. Surf. Area m²/g	COLE cm/cm	Water disp. clay %	Clay % w/w
0-3	-	-	-	-	64.9
3-13	-	-	-	-	45.7
13-33	-	-	-	-	50
33-65	-	-	-	-	47.8
65-89	-	-	-	-	63.4
89-113	-	-	-	-	64
113-153	-	-	-	-	53
153-213	-	-	-	-	81.5

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
0-3	6.6	6.2	0.36	-	11.27	0.88	13	-	-	30.1	6.8	2.8	0.0	39.7
3-13	6.4	5.8	0.35	-	3.63	0.35	10	-	-	15.8	4.2	2.2	0.1	22.3
13-33	6.3	5.5	0.22	-	2.71	0.27	10	-	-	12.4	4.3	2.5	0.1	19.3
33-65	6.1	5.0	0.14	-	1.49	0.14	11	-	-	8.2	3.8	2.3	0.1	14.4
65-89	5.9	4.8	0.15	-	1.07	-	-	-	-	8.4	3.4	1.7	0.1	13.6
89-113	6.1	4.9	0.14	-	0.79	-	-	-	-	-	3.2	1.3	0.1	4.6
113-153	6.1	5.0	0.12	-	0.38	-	-	-	-	7.8	3.0	1.1	0.2	12.1
153-213	6.6	5.4	0.15	-	0.31	-	-	-	-	8.7	4.0	1.3	0.1	14.1

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 %
0-3	67	59	91	39.4	-	-	-
3-13	65	34.4	75	12.7	-	-	-
13-33	63	30.7	61	9.5	-	-	-
33-65	52	27.6	58	5.2	-	-	-
65-89	56	24.5	39	3.7	-	-	-
89-113	-	23.9	37	2.8	-	-	-
113-153	50	24	45	1.3	-	-	-
153-213	59	23.8	29	1.1	-	-	-

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
0-3	-	-	-	0.24	0.07	5.74	0.28	0.08	0.03	-	0.48
3-13	-	-	-	0.25	0.1	5.98	0.28	0.05	0.02	-	0.55
13-33	-	-	-	0.25	0.11	5.84	0.27	0.04	0.02	-	0.51
33-65	-	-	-	0.32	0.09	6.14	0.28	0.03	0.02	-	0.51
65-89	-	-	-	0.2	0.1	5.95	0.27	0.03	0.05	-	0.43
89-113	-	-	-	0.2	0.07	6.23	0.29	0.03	0.05	-	0.42
113-153	-	-	-	0.21	0.12	6.44	0.31	0.02	0.03	-	0.33
153-213	-	-	-	0.22	0.12	7.05	0.34	0.01	0.01	-	0.34

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
0-3	17.3	1.47	10.5	1.64	0.36	-	39.7	1.12
3-13	19.8	0.67	12	1.76	0.28	-	48.1	1.26
13-33	20.9	0.53	12.5	1.81	0.3	-	47.9	1.31
33-65	21.5	0.41	12.8	1.90	0.32	-	48.8	1.34
65-89	23.0	0.34	13	1.77	0.27	-	50.8	1.32
89-113	22.7	0.34	13.2	1.61	0.26	-	47.1	1.33
113-153	22.4	0.32	15	1.63	0.28	-	46.0	1.28
153-213	26.3	0.31	15.3	1.30	0.27	-	45.0	1.36

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
0-3	2.6	25.4	0.62	0.21	3.9	10.1	2.8
3-13	2.6	13.9	0.71	0.14	4.1	10.7	3.0
13-33	2.6	12.6	0.76	0.12	3.9	10.2	2.8
33-65	2.6	9.9	0.69	0.07	3.9	10.1	2.8
65-89	2.8	10.1	0.64	0.06	3.7	10.4	2.8
89-113	2.7	10.1	0.65	0.06	3.5	9.5	2.6
113-153	2.3	10.1	0.96	0.05	3.5	8.2	2.4
153-213	2.7	10.5	0.44	0.06	2.9	7.8	2.1

Clay mineralogy

Depth (cm)	Chlorite	Feldspar	Gibbsite	Goethite	Halloysite	Hematite	Kaolinite	Mica / illite	Mixed-layer	Quartz	Smec	Vermiculite
0-3	-	weak	-	very weak	-	-	weak to medium	very weak to weak	strong	very weak to weak	-	-
3-13	-	weak	-	very weak to weak	-	-	weak to medium	very weak to weak	strong	very weak to weak	-	-
13-33	-	weak	-	very weak	-	-	weak to medium	very weak to weak	strong	very weak to weak	-	-
33-65	-	weak	-	very weak to weak	-	-	medium to strong	very weak to weak	strong	very weak to weak	-	-
65-89	-	weak	-	very weak	-	-	medium to strong	very weak to weak	strong	very weak to weak	-	-
89-113	-	weak	-	very weak	-	-	medium to strong	very weak to weak	strong	very weak	-	-
113-153	-	weak	-	very weak	-	-	medium to strong	very weak to weak	strong	very weak to weak	-	-

Profile description

10-35 cm

(5YR 2/2, dry) dark reddish brown (5YR 3/2, moist)dark reddish brown (5YR 3/3, moist),clay,clay loam,moderate medium subangular blocky,very fine and fine crumb,slightly hard very friable slightly sticky slightly plastic,slightly hard very friable sticky plastic,patchy thin clay cutans,many fine pores and common medium pores,many fine to coarse pores,clear smooth boundary to,gradual wavy boundary to,

Bt1 35-115 cm

dark brown (10YR 3/3, moist)clay,moderate medium angular blocky,slightly hard very friable sticky plastic,broken clay on pedfaces cutans,many fine pores and common medium pores,few small soft ferruginous nodules few small soft manganiferous nodules,

Kind 1 (parent material) ; Parker (eds), 1984	fine-grained igneous rock
Mode of accumulation or deposition of parent material	unconsolidated, unspecified
Remarks on Parent Materials	Trachytes

Altitude	2170m
Physiographic Unit	rolling volcanic upland
Slope	0%
Topography; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	rolling

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Reference soil Kenya 15: Nitisol

Characteristics

Reference soil KE015: Nitisols

Classification