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Chapter 3
Land resources (continued)

3.2 Soil Resources (continued)

TABLE 3.16
Extents of soil units

SymbolSoil unit nameExtent (ha)% total area
AAcrisols45 0800.08
AcChromic Acrisols82 8300.14
AgGleyic Acrisols49 9500.09
AhHumic Acrisols151 3450.26
AicFerralo-chromic Acrisols772 6851.34
AifFerralo-ferric Acrisols127 7600.22
AioFerralo-orthic Acrisols325 4750.56
AoOrthic Acrisols167 9200.29
ApPlinthic Acrisols14 8800.03
AthAndo-humic Acrisols14 6000.03
BCambisols8 8000.02
BcChromic Cambisols1 000 7001.74
BdDystric Cambisols70 3500.12
BeEutric Cambisols630 1401.09
BfFerralic Cambisols53 8400.09
BgGleyic Cambisols31 1500.05
BhHumic Cambisols513 1850.89
BkCalcic Cambisols1 890 6303.28
BncNito-chromic Cambisols296 1950.51
BtcAndo-chromic Cambisols436 6000.76
BteAndo-eutric Cambisols181 7500.32
BvVertic Cambisols20 8250.04
ChHaplic Chernozems39 8000.07
CkCalcic Chernozems56 8000.10
EcCambic Renzinas14 7000.03
EoOrthic Renzinas184 7900.32
FFerralsols128 0800.22
FaAcric Ferralsols59 4000.10
FhHumic Acrisols6 1000.01
FnhNito-humic Ferralsols13 6000.02
FnrNito-rodic Ferralsols225 9000.39
FoOrthic Ferralsols855 4901.49
FrRodic Ferralsols2 695 0154.68
FxXanthic Ferralsols73 8600.13
G/GeGleysols/Eutric Gleysols9 2700.02
GcCalcaric Gleysols95 1000.17
GdDystric Gleysols22 6100.04
GhHumic Gleysols52 8300.09
GmMollic Gleysols124 8400.22
GvVertic Gleysols820 0701.42
HgGleyic Phaeozems147 1800.26
HhHaplic Phaeozems96 3550.17
HnlNito-luvic Phaeozems21 9000.04
HolOrthic-luvic Phaeozems319 1200.55
HrlChromo-luvic Phaeozems523 2700.91
HthAndo-haplic Phaeozems36 1900.06
HtlAndo-luvic Phaeozems263 9800.46
HvlVerto-luvic Phaeozems642 2251.11
ILithosols2 344 0454.07
IrIronstone soils216 2850.38
JFluvisols34 8000.06
JcCalcaric Fluvisols1 434 6002.49
JeEutric Fluvisols299 4000.52
JtThionic Fluvisols79 6500.14
KhHaplic Kastanozems57 6400.10
LLuvisols194 7500.34
LaAlbic Luvisols124 6250.22
LcChromic Luvisols2 321 8804.03
LfFerric Luvisols582 1501.01
LgGleyic Luvisols167 3950.29
LicFerralo-chromic Luvisols784 8401.37
LifFerralo-ferric Luvisols44 9550.08
LioFerralo-orthic Luvisols50 3250.09
LkCalcic Luvisols981 9951.70
LncNito-chromic Luvisols34 1200.06
LnfNito-ferric Luvisols36 2601.81
LoOrthic Luvisols1 039 8550.29
LvVertic Luvisols169 7100.12
MoOrthic Greyzems70 7000.07
MvoVerto-orthic Greyzems38 1000.05
NdDystric Nitisols31 1950.05
NeEutric Nitisols600 6101.04
NhHumic Nitisols635 8601.10
NmMollic Nitisols190 6100.33
NthAndo-humic Nitisols212 5300.37
NveVerto-eutric Nitisols33 3650.06
NvmVerto-mollic Nitisols3 2400.01
OdDistric Histosols79 8000.14
QArenosols15 7500.03
QaAlbic Arenosols63 8800.11
QcCambic Arenosols702 7901.22
QfFerralic Arenosols2 200 8903.82
QkcCalcaro-cambic Arenosols446 7800.78
QlLuvic Arenosols187 8600.33
RRegosols13 2500.02
RcCalcaric Regosols1 256 1102.18
RdDystric Regosols138 6400.24
ReEutric Regosols696 3901.21
RtcAndo-calcaric Regosols301 4400.52
SSolonetz634 5801.10
SgGleyic Solonetz434 0300.75
SloLuvo-orthic Solonetz4 664 1008.10
SmMollic Solonetz43 8200.08
SoOrthic Solonetz2 536 7304,40
ThHumic Andosols455 5200.79
TmMollic Andosols528 9500.92
TvVitric Andosols81 6000.14
URankers154 6700.27
VVertisols149 5800.26
VcChromic Vertisols763 9201.33
VpPellic Vertisols1 514 3902.63
WPlanosols4 3800.01
WdDystric Planosols114 2050.20
WhEutric Planosols323 7100.56
WeHumic Planosols195 8000.34
WsSolodic Planosols2 472 4054.29
WveVerto-eutric Planosols251 2050.44
XXerosols/Yermosols102 9200.18
XhHaplic Xerosols/Yermosols650 6201.13
XkCalcic Xerosols/Yermosols3 620 6706.29
XyGypsic Xerosols/Yermosols168 5000.29
ZSolonchaks577 7501.00
zgGleyic Solonchaks187 0000.32
ZoOrthic Solonchaks1 601 4102.78
ZtTakyric Solonchaks147 8000.26
Lava 1 015 9601.76
Lava flows 128 9900.22
Lava fields 56 4600.10
Rock outcrops 557 8850.97
Ice cap 5 3350.01
Lakes 117 6000.20
Towns 10 7000.02
Total extent 57 607 200100.00

3.2.6 Soil Textures

Soil textures may vary within the range of textures defined for a particular soil unit. In the legend of the Exploratory Soil Map textural classes for individual soil units by soil mapping unit are presented. The three major textural divisions are subdived into 17 classes. The three major textural divisions are shown in the texture diagram.

Textural classes by major division are also listed below; percentage occurrence is presented in Table 3.17.

TABLE 3.17
Percentage occurrence of textural classes Texture class Texture Percentage

Texture classTexture symbolPercentage 1
Loamy coarse sandLCS0.5
Fine sandFS0.2
Loamy fine sandLFS0.8
Loamy sandLS3.8
I Coarse textures 5.5
Fine sandy loamFSL1.3
Sandy loamSL3.1
Sandy clay loamSCL15.4
Silt loamSL0.6
Clay loamCL28.5
Silty clay loamSICL0.4
I Medium textures 55.8
Sandy claySC10.2
Silty claySIC0.3
Peaty clayPC<0.1
I Fine textures 38.7

1 Total extent where texture is applicable is 55 714 270 ha (96.9% of total area).

Coarse textures- Sand
- Loamy coarse sand
- Fine sand
- Loamy fine sand
- Loamy sand
Medium textures- Fine sandy loam
- Sandy loam
- Loam
- Sandy clay loam
- Silt loam
- Clay loam
- Silty clay loam
- Silt
Fine textures- Sandy clay
- Silty clay
- Peaty clay

3.2.7 Soil Stoniness

The presence of coarse material (stoniness) in the soil profile has been inventoried separately from soil textures. The presence of coarse material is subdivided into six types:

Gravely (G)
Very gravely (VG)
Stony (S)
Bouldery (SB)
Stony/bouldery (SB)
Bouldery/stony (BS)

3.2.8 Soil Phases

Soil phases indicate land characteristics which are not considered in the definition of the soil units but are significant to the use and management of land. The soil phases recognized on the Exploratory Soil Map of Kenya can be grouped into phases indicating a mechanical hindrance or limitation (rocky, bouldery, boulder-mantle, stony, stone-mantle, gravel-mantle); phases indicating an effective soil depth limitation (lithic, paralithic, petro-calcic, piso-calcic, petro-ferric, piso-ferric); and phases indicating a physico-chemical limitation (saline, sodic and saline-sodic). Soil phases can occur alone (one soil phase or in combination (two or three phases). Some of these phases have been defined in the FAO-Unesco Legend, while others have been introduced in the Exploratory Soil Map. The soil phases and their extents are presented in Table 3.18.

3.2.9 Soil Mapping Unit Composition

At the exploratory level a soil mapping unit only rarely comprises a single soil; usually it consist of one main soil with minor associates. When the various soils of a soil mapping unit occur in a recognizable geographical pattern in defined proportions, they constitute a soil association; if such a pattern is absent, they form a soil complex.

The productivity potential of different soil units within a soil mapping unit consequently may vary widely. The suitability of soil association (soil complex) for specific use cannot be assessed without taking account of each individual soil unit within the association.

The legend of the Exploratory Soil Map does not provide explicit information in a quantified manner on the composition of the soil mapping units. This however has been provided to FAO by Stiboka in Wageningen in close cooperation with Kenya Soil Survey in Nairobi and the International Soil Reference and Information Centre in Wageningen (van der Pouw 1983).

The complete mapping unit composition table is presented in Technical Annex 1. This table consists of the percentage allocation of soil units by slope class, soil texture and soil phases for each soil mapping unit, and of information on landform and geology/parent material.

The composition of a example soil association (Ps3) is illustrated and explained in Figure 3.11.

3.3 Land Use Overlays

The land use and tse-tse infestation overlays have been integrated into the physical resources inventories. Consequently each agro-ecological cell is further characterized by the information contained in these overlays.

TABLE 3.18
Extents (%) of soil phases

Soil phaseSymbolPercentage1
One soil phase 62.8
Rocky and boulderyR and B3.7
Rocky and stonyR and S2.9
Bouldery and stonyB and S3.6
Boulder-mantle and saline-sodicBM and AO1.1
Stony and rockyS and R0.3
Stony and boulderyS and B<0.1
Stony and petrocalcicS and K<0.1
Stony and saline-sodicS and AO1.0
Stone-mantle and sodicSM and 01.0
Stone-mantle and saline-sodicSM and AO0.1
Lithic and rockyP nd R1.8
Lithic and boulderyP and B1.1
Lithic and boulder-mantleP and BM1.3
Lithic and stonyP and S2.6
Lithic and sodicP and O<0.1
Lithic and saline-sodicP and AO0.1
Paralithic and rockyPP and R<0.1
Paralithic and stonyPP and S0.7
Petrocalcic and stonyK and S1.6
Petrocalcic and saline-sodicK and AO<0.1
Petrocalcic and salineKK and A0.1
Petrocalcic and sodicKK and O0.1
Pisoferric and rockyN and R0.1
Pisoferric and petroferricN and M0.2
Pisoferric and fragipanA and F0.1
Sodic and fragipanO and F0.1
Two soil phases 23.7
Rocky and bouldery and saline-sodicR and B and AO1.1
Rocky end lithic and stonyR and P and S0.1
Bouldery and stony and salineB and S and A0.2
Bouldery and stony and saline-sodicBM and S and AO0.8
Lithic and rocky and boulderyP and R and B0.2
Lithic and rocky and stonyP and R and S2.8
Lithic and bouldery end stonyP and B and S0.2
Lithic and bouldery and salineP and B and A1.0
Lithic and boulder-mantle and saline-sodicP and BM and AO1.1
Lithic and stony and rockyP and S and R0.8
Lithic and stony and salineP and S and A0.6
Lithic and stony and saline-sodicP and S and AO0.1
Lithic and stone-mantle and saline-sodicP and SM and AO3.2
Lithic and gravel-mantle and salineP and GM and S1.3
Three soil phases 13.5

1 Total extent where soil phases occur is 28,096,674 ha (48.9 % of total area)

Example of soil mapping unit composition of soil mapping unit Ps3


TABLE 3.19
Extents of cash crop zones

CropCrop descriptionExtent (ha)Percentage area
012Tea (secondary)422 6008.37
023Coffee (secondary)441 7008.75
034Sugarcane (secondary)848 50016.81
045Cotton (secondary)923 80018.30
056Pyrethrum464 9009.21
067Sisal (secondary)584 60011.58
108Tea (primary)67 5001.34
129Tea/Coffee144 0002.85
1310Tea/Sugarcane55 8001.11
1511Tea/Pyretrum53 3001.06
2012Coffee (primary)50 8001.01
2313Coffee/Sugarcane103 6002.05
3014Sugarcane (primary)69 2001.37
3415Sugarcane/Cotton289 4005.73
4017Cotton (primary)341 0006.76
6018Sisal (primary)170 9003.39
7019Pineapple (primary)16 0000.32
Total extent  5 047 600100.00

TABLE 3.20
Extents of forest zones

ForestForest descriptionExtent (ha)Percentage area
F12Registered Forest1 522 00077.09
F23Unregistered Forest60 0003.04
F34Proposed Forest392 30019.87
Total extent  1 974 300100.00

TABLE 3.21
Extents of parkland areas

ParklandParkland descriptionExtent
Percentage area
P12National park2 820 30067.18
P23Game reserve890 50021.21
P34National reserve487 30011.61
Total extent  4 198 100100.00

Tables 3.19, 3.20, 3,21, 3.22 and 3.23 present descriptions, map symbols, computer coding and extents of map units respectively of cash crop zones, forest zones, parkland areas, irrigation schemes and tse-tse infestation areas. Figures 3.12, 3.13, 3.14, 3. 15 and 3.16 present generalized maps of the above information and the details are presented in Technical Annex 3.

TABLE 3.22
Extents of initiation schemes

Irrigation areaNameExtent
Percentage area
067Ahero I2 0004.91
078Ahero II2 5006.14
089Marigat1 2002.95
0910Mwea13 20032.43
1011Malka daka4000.98
1314Garisa1 0002.46
1415Hola2 7006.63
1517Garsen2 4005.90
1920Bura (proposed)10 90026.78
Total extent  40 700100.00

TABLE 3.23
Extent of tse-tse infestation areas

Tse-tse infestation areas Extent
Percentage total area
T27 561 00013.15

3.4 Computerized Land Resources Inventory

The computerized land resources inventory for Kenya records total extents of agro-ecological cells. Each cell contains information on the following:

-   Sequence number (NUM)

-   Province (PRV)

-   District (DIST)

-   Thermal Zone (TZ)

-   Length of Growing Period Zone (LGP)

-   Pattern of Length of Growing Period Zone (PAT)

-   Soil Mapping Unit (MPU)

-   Landform (LNDFM)

-   Geology/Parent Material (GEO)

-   Soil Unit (SOIL)

-   Soil Texture (TXT)

-   Soil Phases 1st, 2nd and 3rd (PHASES)

-   Cash Crop Zone (CROP)

-   Forest Zone (FOR)

-   Irrigation Scheme (IRR)

-   Tse-tse Infestation Areas (TSE)

-   Parkland Area (PARK)

-   Extent in hectares (EXTENT).

The land resources inventory of Kenya consists of about 91 000 unique agro-ecological cells. For Kiambo District (code: 1) in Central Province (code: 1), the complete land resources inventory (651 cells) is presented in Technical Annex 1.

The computerized land resources inventory is available on diskettes (ASCII), in the form of a grid based geographic information system (GIS). For details on formats of the land resources inventory and the use of the geographic information system, reference should be made to Technical Annex 7.

Generalized map of cash crop zones


Generalized map of forest zones


Generalized map of parkland areas


Generalized map of irrigation schemes


Generalized map of tse-tse infestation areas


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