This document provides an overview of Nitisols, one of the 30 soil groups in the FAO soil classification system. Some key points: - Nitisols are deep, red, well-drained tropical soils with more than 30% clay content and a blocky structure. They are found in tropical and subtropical regions like Africa and Asia. - They have a clayey 'nitic' subsurface horizon formed from weathered intermediate to basic parent rock. Common clay minerals include kaolinite and halloysite. - Though low in available phosphorus and bases, Nitisols have high agricultural potential due to their depth, structure, drainage, and moisture-holding capacity. They support crops and

1. College of agriculture
Department of Natural resource management
[ Msc.in water shade management program]
Review on Nito soil
Name. Melkamu Tadese
I.D pgw/62383/14
Submitted to Belete.L[ ass.pro]

3.  Introduction
Nitisol, one of the 30 soil groups in the classification system of
the Food and Agriculture Organization (FAO). Nitisols are
technically defined by a significant accumulation of clay (30
percent or more by mass and extending as much as 150 cm [5
feet] below the surface) and by a blocky aggregate structure.
The Reference Soil Group of the Nitisols accommodates deep,
well-drained, red, tropical soils with dif-fuse horizon
boundaries and a subsurface horizon with more than 30
percent clay and moderate to strong angular blocky structure
elements that easily fall apart into characteristic shiny,
polyhedric (‘nut-ty’) elements.

4. Definition of Nitisols
 A nitisol in the World Reference Base for Soil Resources
(WRB) is a deep, red, well-drained soil
 clay content of more than 30% and a blocky structure.
 Nitisols correlate with the kandic alfisols, ultisols and
inceptisols of the USDA soil taxonomy.
 These soils are found in the tropics and subtropics;[]
 For exampel, the tropical highlands of Ethiopia, Kenya,
Democratic Republic of the Congo and Cameroon.
 Nitisols form from fine-textured material weathered from
intermediate to basic parent rock and kaolinite, halloysite
and iron oxides dominate their clay mineralogy.

5.  The natural vegetation on nitisols includes tropical rain forest
and savannah.
 Limitations frequently include low phosphorus availability
and low base status, but, deep, stable soils have high
agricultural potential, and are often planted to crops.

6. Summary description of Nitisols
 Connotation deep, red, well-drained tropicalsoils .
 Have {clayey ‘nitic subsurface horizon.
 Parent material finely textured weathering products of
intermediate to basic parent rock.
 The clay assemblage of Nitisols is dominated by kao-
linite/(meta)halloysite.
 Nitisols are rich in iron and have little water-dispersible
clay. Environment Nitisols are predominantly found in level
to hilly land under tropical rain forest or savan-na
vegetation.

7. Profile development
 Profiles is Red or reddish brown clayey soils with a ‘nitic’
subsurface
 ho-rizon of high aggregate stability.
 Use Nitisols are planted to farm and plantation crops.
 They are generally considered to be ‘fertile’ soils in spite of
their low level of ‘available’ phosphorus and their normally
low base status.
 Nitisols are deep, stable soils with favourable physical
properties.

8. Regional distribution of Nitisols
 There are approximately 200 million hectares of
Nitisols worldwide.
 More than half of all Nitisols are found in tropical
Africa, notably in the highlands (>1000 m.) of
Ethiopia, Kenya, Zaire and Cameroon.
 Elsewhere, Nitisols are well represented at lower
altitudes, e.g. in tropical Asia, South America, Central
America and Australia.

9. Associations with other Reference Soil Groups
 Relationships between Nitisols and other Reference Soil
Groups are quite diverse
because they are conditioned by a score of (localized) factors.
presents common lateral linkages between Nitisols and other Soil
Groups.
1, In undulating landscapes ,
2, In volcanic landscapes , weathered.
3,In uplifted and dissected landscapes on old surfaces,
4, In landscapes on limestone,
.

10. Characteristics of Nitisols
 Morphological characteristics Nitisols are normally
deeper than 150 cm and dark red in colour.
 They are well-drained soils with a clayey subsurface
horizon.
 The relative decrease of the clay content of this ‘nitic
horizon’ is gradual (less than 20 percent from its maximum
at 150 cm below the surface).
 Horizon boundaries are typically gradual or diffuse.
 also may acquire properties found in vertic or Ferric
horizons.

11. Hydrological characteristics
Nitisols are
 free-draining soils and
 permeable to water (50–60 percent pores).
Their retention of ‘plant-available’ moisture is only fair
(5-15 percent by volume)
but total moisture storage is nonetheless sat- is factory
because the rootable soil layer extends to great depth,

12. Physical characteristics
Nitisols are hard when dry, very friable to firm when
moist and sticky and plastic when wet. Gravel or stones
are rare but fine iron-manganese concretions (‘shot’) may
be found.

13. Chemical characteristics
The cation exchange capacity of Nitisols is high. if compared to that of
other tropical soils such as
 Ferralsols
 Lixisols and
 Acrisols
The reasons are:
1, Although the clay assemblage is dominated by low-activity clays, the
clay content is high
2, Soil organic matter makes a considerable contribution to the overall
horizon.
The soil-pH (H2O) is typically between 5.0 and 6.5;

14. Biological characteristics
 Intense faunal activity is held accountable for the
typical gradual horizon.
 volcanic glass deposited on the (present) surface was
found back at a depth of 7 meters in Nitisols in Kenya.

15. Management and use of Nitisols
 Nitisols are among the most productive soils of the
humid tropics.
 The deep and porous solum and the stable soil structure
of Nitisols permit deep rooting and make these soils
quite resistant to erosion.
 The good workability of Nitisols, their good internal
drainage and fair water holding properties are comple-
mented by chemical (fertility) properties that compare
favourably to those of most other tropical soils.

16.  Nitisols have relatively high contents of weathering
minerals and surface soils may consist for several
percent of organic matter, in particular under forest or
tree crops.

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