Reference soil Kenya 26: Nitisol

KE026

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 KE026: Nitisols

A very deep, red, fine clayey soil, with a good structure and high biological activity, formed by weathering of andesite (?) rock. Fine and very fine grass roots are well distributed throughout the profile up to a depth of 400 cm. Many small soft manganese concretions between 205-210 cm occur. Below 270 cm there are continuous ferro-manganese coatings increasing with depth. This is the most important soil series of the area.

Classification

WRB 2006

WRB 1998

Umbric-Acric- Nitisol (Humic)

Humi-Umbric- Nitisol (Dystric)

0-79 cm	umbric horizon
79-270 cm	nitic horizon

FAO-UNESCO-ISRIC 1988

FAO-UNESCO-ISRIC 1974

Umbri-Humic Nitisol

Humic Nitosol

0-79 cm	umbric A horizon
40-270 cm	argic B horizon
-	nitic
-	strongly humic

0-79 cm	umbric A horizon
40-270 cm	argillic B horizon

Local classification:	Magombo series

Other classification

USDA-SCS (1975)

Palehumult udic kaolinitic

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
0-20	-	0.1	0.5	1.3	2.7	2.4	7	8.5	27.7	36.2	56.8
20-40	-	0.5	0.7	1.2	2.6	2.7	7.7	12.7	29.5	42.2	50.2
40-60	-	0.2	0.5	1.0	2.2	2.2	6.1	10.2	22.2	32.4	61.4
60-100	-	0.1	0.4	1.0	2.3	2.3	6.1	8.5	19.0	27.5	66.6
100-150	-	0.2	0.3	0.7	1.9	1.9	5	8.1	18.5	26.6	68.5

Water retention characteristics

Depth (cm)	Bulk density kg/dm³	Spec. Surf. Area m²/g	COLE cm/cm	Water disp. clay %	Clay % w/w
5-10	0.88	-	-	-	-
0-20	-	-	-	7.3	56.8
20-40	-	-	-	7.2	50.2
15-20	0.88	-	-	-	-
70-75	1.09	-	-	-	-
40-60	-	-	-	23.9	61.4
108-113	1.02	-	-	-	-
60-100	-	-	-	26.7	66.6
100-150	-	-	-	-	68.5

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
5-10	0.88	60.2	55.1	45.6	36.9	34.3	32.5	30.9	18.4
15-20	0.88	64.7	60.5	48.5	40.3	38.2	34.5	20.9	18.3
70-75	1.09	58.7	51.2	44.1	40.5	39.6	37.8	28.5	27.0
108-113	1.02	57.8	54.1	47.4	44.1	42.7	40.9	26.2	24.9

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
0-20	5.4	4.5	0.27	-	4.87	0.50	10	0.3	0.0	8.9	2.8	1.8	0.0	13.5
20-40	5.4	4.4	0.11	-	3.45	0.36	10	0.6	0.2	5.8	2.4	0.8	0.1	9.1
40-60	5.3	4.5	0.23	-	2.40	0.21	11	0.3	0.0	6.9	2.8	0.6	0.4	10.7
60-100	5.2	4.5	0.09	-	1.34	0.13	10	0.3	0.2	3.7	2.7	0.5	0.1	7
100-150	4.8	4.1	0.08	-	0.63	-	-	1.3	0.9	1.3	1.5	0.6	0.1	3.5

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 %
0-20	46	29.1	21	17.0	-	0	0
20-40	39	23.2	24	12.1	-	2	0
40-60	55	19.5	18	8.4	-	0	2
60-100	40	17.6	19	4.7	-	3	1
100-150	27	12.8	15	2.2	-	21	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
0-20	-	70	-	0.7	0.3	7.1	0.9	-	-	-	1.3
20-40	-	82	-	1.0	0.3	7.3	1.0	-	-	-	1.3
40-60	-	73	-	0.6	0.3	7.4	0.8	-	-	-	1.4
60-100	-	74	-	0.5	0.2	7.6	0.9	-	-	-	1.2
100-150	-	77	-	0.5	0.3	7.7	0.8	-	-	-	1.4

Clay mineralogy

Depth (cm)	Chlorite	Feldspar	Gibbsite	Goethite	Halloysite	Hematite	Kaolinite	Mica / illite	Mixed-layer	Quartz	Smec	Vermiculite
0-20	-	very weak	-	very weak	-	-	very strong	very weak	very weak	very weak	-	-
40-60	-	very weak	-	very weak	-	-	medium	very weak	very weak	very weak	-	-

Profile description

Ah1 0-50 cm	dark reddish brown (5YR 3/2, moist)clay,moderate fine subangular blocky,very friable slightly sticky slightly plastic,many very fine and fine and few common medium and coarse pores,very fine and fine roots,non calcareous,clear smooth boundary to,
Ah2 50-79 cm	dark reddish brown (5YR 3/3, moist)clay,moderate fine subangular blocky,friable slightly sticky slightly plastic,many fine and very fine pores and common medium pores,very fine and fine roots,non calcareous,gradual smooth boundary to,
Bw1 79-270 cm	(5YR 3.5/4, moist)clay,moderate fine angular blocky and moderate fine subangular blocky,friable slightly sticky slightly plastic,many fine and very fine pores and few medium pores,very fine and fine roots,small soft manganiferous concretions,non calcareous,clear smooth boundary to,
Bw2 270-700 cm	yellowish red (5YR 4/6, moist)clay,moderate medium angular blocky,firm slightly sticky slightly plastic,broken thick clay cutans,common very fine and fine pores,non calcareous,gradual smooth boundary to,
Bw3 700-750 cm	yellowish red (5YR 4/6, moist)clay,moderate medium and coarse prismatic,firm slightly sticky slightly plastic,patchy thick clay cutans,common very fine and fine pores,non calcareous,

Kind 1 (parent material) ; Parker (eds), 1984	andesite
Mode of accumulation or deposition of parent material	residual material
Texture of parent material	clayey
Weathering Resistance	poor
General characterization of the status of weathering of solid rock	highly

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	cultivated pasture
Rotation scheme ; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	crop rotation scheme not relevant
Major vegetation type; Guidelines for soil description - Fourth edition (FAO, Rome, 2006)	grassland

Altitude	1880m
Physiographic Unit	saddle between hill tops
Physiographic position of the site	slope
Regional landform; McDonald, R.C., Isbell, R.F. et all, 1984; Australian soil and land survey Field Handbook, Inkata Press, Melbourne.	hill
Slope	5%
Form of the slope surrounding the site	straight
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
Depth to groundwater table	0cm
Kind of ground water table (USDA, 1979)	no groundwater table observed
Estimated permeability (class) of least permeable part of the profile	moderate
Estimated run off (class)	slow

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

Characteristics

Reference soil KE026: Nitisols

Classification