Soils of Assam

This slide is about the various types of soils found in Assam. It gives a highlight on various characteristics of soils, their pH value, deficiency and the places where they occur.

1. SOILS OF ASSAM Dr. BEEJATA DAS ASSISTANT PROFESSOR DEPARTMENT OF GEOGRAPHY S.P.P. COLLEGE NAMTI, SIVASAGAR, ASSAM, INDIA

2. Introduction Soil is the thin surface- layer on the earth comprising mineral particles formed by the break- down of rocks, decayed organic materials, living organisms, water and soil. Importance of Soil Soil is a very important natural resource of Assam because agricultural production is basically dependent on the fertility of soil.

3. Factors affecting soil formation Geology, topography and climate seem to play vital roles in the soil formation of Assam.

4. GROUPS OF SOIL ALLUVIAL SOILS PIEDMONT SOILS HILL SOILS LATERITIC SOILS YOUNGER ALLUVIAL OLDER ALLUVIAL RED SANDY SOILS RED LOAMY SOILS

5. ALLUVIAL SOILS These soils are by far the largest and the most important soil group of Brahmaputra and Barak Plain. Alluvial soils are developed from the deposition of the products of weathering of rocks constituting the Himalayas by the river Brahmaputra. They are acidic in reaction. Soils on the northern bank of the Brahmaputra are less acidic than those on the southern bank.

6. The alluvial soils contain moderate amounts of organic matter and nitrogen and high amounts of phosphorous and potash. Soils of the Barak valley contain more humus then those of the Brahmaputra valley. The soils of the Brahmaputra valley are richer in total magnesium.

7. NEWER OR YOUNGER ALLUVIAL SOILS These soils are found in the north and south bank plains including the active flood plains of the Brahmaputra and Barak rivers. Colour : They are moderately deep to very deep and grey to molted grey. Texture: They are mostly sandy to silty loams. The new alluvial soils of the Brahmaputra valley are of a coarser texture while soils of the Barak valley are of a finer texture.

8. pH: These soils are less acidic and are often neutral in reaction. Deficiency: They are deficient in phosphoric acid, nitrogen and humus.

9. OLDER ALLUVIAL SOILS This soil occurs in some patches of Kokrajhar , Barpeta , Nalbari , Kamrup , Darrang , Sonitpur , Lakhimpur and Dhemaji districts between the northern piedmont soil belt and the southern new alluvial soils of the Brahmaputra valley. It occurs in a narrow belt in the south bank districts of the Brahmaputra valley. In the Kopili plain covering Nagaon district the old alluvium finds wider extension, Barak plain also has some elongated patches of old alluvium confined between the new alluvial soils of the active floodplain and the hill soils bordering Mizoram.

10. Colour : These soils are very deep, brownish to yellowish brown in colour . Texture: They are mostly fine loams to coarse loams. pH: These soils are slightly to moderately acidic.

11. PIEDMONT SOILS The piedmont soils comprise the Bhabar and the Tarai soil covering respectively the Bhabar and Tarai belt of the Brahmaputra valley. Occurrence: These soils are confined to the northern narrow zone along the piedmone zone of the Himalayan foothills. The Bhabar soil occurs in the narrow Bhabar zone along Assam- Arunachal border extending east upto the river Subansiri . The Tarai soil occurs just south of the Bhabar soils extends upto the Dihang river in some discontinuous narrow patches.

12. Colour : The Bhabar soil is deep to very deep in colour . Texture: The Bhabar soil is coarse loamy in texture whereas the Tarai soils varies from sandy to slity loams that remain saturated.

13. HILL SOILS Occurrence: They are found in the southern hilly terrains of the state. RED SANDY SOILS Occurrence: They are found in a narrow belt along the Assam- Meghalaya border, the Karbi Plateau, southern part of the Barail ranges of Dima Hasao district and some parts of the foothills along the eastern border of the Cachar district.

14. Colour : They are very deep, well drained and brownish to yellowish red in colour . Texture: The texture of these soils varies from sand to clay. Deficiency: These soils are poor in lime, manganese, phosphates, nitrogen and humus.

15. RED LOAMY SOILS Occurrence: These soils occur in the narrow southern foothill belt running along Assam’s border with Arunachal and Pradesh Nagaland and also in the southern fringes of the Karbi Plateau and the Barail hills of Dima Hasao district also along the Assam- Mizoram border.

16. Colour : They are deep, dark grayish brown to yellowish red in colour . Texture: These soils are fine to coarse loamy in texture. pH: They are lightly to moderately acidic. Deficiency: These soils lack in nitrogen, phosphoric acid, humus and lime.

17. LATERITIC SOILS Occurrence: These soils occur extensively almost over the Dima Hasao district covering some parts of southern Karbi Plateau while few patches are confined to eastern margin of the Hamren sub- division of Karbi Anglong district, southern border of Golaghat district and the northern part of the Barak Plain along the foothills of the Barail range.

18. Colour : These soils are dark in colour . Texture: They are finely textured with heavy loams. Deficiency: These soils are deficient in nitrogen, potash, phosphoric acid and lime.  

19.   REFERENCES Bhagabati , A.K., et al. (2007). Geography of Assam , Rajesh Publications, New Delhi. Khullar , D.R. (2005). India- A Comprehensive Geography , Kalyani Publishers, New Delhi. Kolay , A.K. (1993). Basic Concepts of Soil Science , Wiley Eastern Limited, New Delhi.