ASSIGNMENTENVIROMENTAL GEOGRAPHY

Department of Geography(M.sc Final)

TOPIC: OXISOL

SUBMITED TO: Dr. IFFAT TABASSUM

SUBMITED BY: JAWAD NADIR R.No:(43)

Session (2015-2016)

SOIL

Soil: Definition• Solid earth material that has been altered(change in

character or composition)by physical, chemical and organic processes so that it can support rooted plant life.

Engineering definition: Anything that can be removed without blasting

Soil classification = Soil orders

• In 1975, Soil Taxonomy was published by the United States Department of Agriculture's Soil Survey Staff. This system for classifying soils has undergone numerous changes since that time, and the 2nd edition was published in 1999. Soil Taxonomy remains one of the most widely used soil classification systems in the world.

• At the highest level, Soil Taxonomy places soils in one of 12 categories known as orders.

Soil classification = Soil orders•Aridisols = arid zone soils (calcic horizons)•Mollisols = grassland soils (thick A horizon)•Alfisols, Ultisols, and •Spodosols = forest soils (thick B horizon)•Oxisols = tropical soils (quite oxidized)•Histosols = wetland soils•Gelisols = polar soils•Andosols = volcanic parent material•Vertisols = swelling clays•Entisols = weak A over C horizon•Inceptisols = weak B horizon

Soil map of world

Greens – Alfisols & mollisolsRed – Oxisols.Tan – Aridosols.

Soil order

OXISOLS

- The Key to the Orders enables the placement of the soil at the Order level. If the soil does not meet the requirements of Gelisols, Histosols, Spodosols, or Andisols, then the soil properties are tested against the requirements for Oxisols.

INTRODUCTION

• Found in tropical and subtropical regions• Areas with high temperature and abundant

precipitation• Climate causes high amounts of weathering• Results

– Soil low in nutrients

OXISOL : MEANING

• The word "oxisol" comes from "oxide" in reference to the dominance of oxide minerals such as Bauxite. In the FAO(food and agriculture organization) soil classification, oxisols are known as ferralsols..

OXISOLS : DEFINITION

• Oxisols (from French oxide, "oxide") are very highly weathered soils that are found primarily in the intertropical regions of the world. These soils contain few weatherable minerals and are often rich in Fe(Ferrous) and Al(Aluminum) oxide minerals.

Oxisols occupy ~7.5% of the global ice-free land area. In the US, they only occupy ~0.02% of the land area and are restricted to Hawaii.

Oxisols only occupy about 23% of the tropics and plinthite (iron-rich, humus-poor mixture of clay with quartz minerals) is less than 1% of all Oxisols.

Oxisols - Suborders Identification of Taxonomic Class

• Aquox: Oxisols that have aquic conditions• Torrox: The suborder of Torrox classifies Oxisols with an aridic

soil moisture regime. (annual average rainfall less than 9.8inch)• Ustox: The suborder of Ustox classifies Oxisols with an ustic or

xeric(containing little moisture; very dry) soil moisture regime.• Perox: The suborder of Perox classifies Oxisols with a perudic

soil moisture regime.• Udox: The suborder of Udox classifies Oxisols with an udic soil

moisture regime(have well-distributed rainfall)

• - S. America has the largest contiguous extent of Oxisols, with Brazil having the largest area.

Zaire has probably the largest extent of Oxisols in Africa..

U.S Land surface• Oxisols are not

found in the continental U.S. in any abundance.

• Only 0.02% of the U.S. has oxisols

• Most oxisols are found in Hawaii. (not the big island)

- In S.E. Asia, Oxisols are present in small isolated areas. Probably the largest area is in Borneo (Kalimantan)

117 - Over 98% of the Oxisols are found in S. America and Africa. S. America has more than 57% of the Oxisols of the world.

Global Distribution of Soil Orders

Order Area ‘000 km2 PercentGelisols 11,869 9.07Histosols 1,526 1.17Spodosols 4,596 3.51Andisols 975 0.75Oxisols 9,811 7.50Vertisols 3,160 2.42Aridisols 15,464 11.82Ultisols 10,550 8.07Mollisols 9,161 7.00Alfisols 13,159 10.06Inceptisols 19,854 15.18Entisols 23,432 17.91Non-soil 7,269 5.56

Oxisols

Formation

Formation

• The main processes of soil formation of oxisols are weathering humification and pedoturbation due to animals. These processes produce the characteristic soil profile. They are defined as soils containing at all depths no more than 10 percent weatherable minerals, and low cation exchange capacity.

• Humification:- is a process in which organic material decompose and break down.

• Pedoturbation:- refers to perturbation that is not caused by illuviation (re-distribution by water.) In clay soils.

The slide shows a diagram illustrating the classic factors of soil formation.

Weathering of a rock is a first step leading to soil formation. In the slide, basalt shows exfoliation (onion structure) due to weathering. The foliation is caused by temperature and moisture changes during the year.

- Climatic and geomorphic processes are not the only processes operating to form or modify the soil. In the tropics, biological activity is very high. Due to the high surface temperatures, many organisms live below ground. The termite nest, seen in the slide, is characteristic of semi-arid landscapes in the tropics.

Oxisol profile • Very fine texture. • High amounts of bioturbation (lots

of animal activity)• Ap - shows topsoil with plowing • Bo1- subsoil with organic material• Bo2- subsoil with slightly different

color• Oxisols are used for agriculture

when fertilizers are added• Provide pineapple and sugarcane

farming• Also support grazing and pasture

lands for livestock.

Characteristics of Oxisols1. Colour

2. Mineralogy

3. Humus Content

4. Structure

5. Vegetation

6. Soil Sustanability

1. COLOUR

Some oxisol have the same bright red colour.

Other may be layered with orange or yellowish colour.

The variation in colour is due to high concentration of iron, AL(aluminum) oxides and hydroxides.

2. Mineralogy:

While the subsurface soil layers contain clay particles, the layer is loaded with hydrous oxides of aluminum and iron. Hydrous oxides are the products of intense weathering of minerals, after much of the silica has leached away from silicate minerals, such as kaolinite..

3.Humus content

Contain little organic matter, therefore little humus.

This is because the Humus content is leached under the impact of heavy precipitation.

4. Structure

This is a 100x magnification of a thin section of an Oxisol from Thailand. The well-structured aggregates

are composed of mixture of kaolinite and Fe oxide .These stable aggregates are responsible for high infiltration and permeability, and this makes

many Oxisols resistant to runoff and erosion.

5. Vegetation

Vegetation: Oxisols may occur under a wide range of vegetational zones including tropical rainforest, scrub and thorn forest, deciduous forest, and savannah (e.g. in the central Brazilian plateau). The use of Oxisols is often limited to shifting cultivation, subsidence farming, low-intensity grazing. Due to amendments Oxisols can be used also for the growth of soybeans, wheat, corn, and coffee..

Soil sustainability Picture from Nigeria (corn field) Crops such as corn are rotated on a yearly

basis. Farmlands are then burned to release

nutrients back into the soil. After 5-10 years land is re-established as

forest.

CONCLUSION

Oxisols are found in warm wet climates.They are generally infertile.Highly permeable.Very resistant to erosion. Their color comes from insoluble Fe and Al

oxides.

Thanks

THE END

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