Soil Types of Nepal

Introduction

The topography of Nepal ranges from 60 to 8848 metre, which is generally classified into 'Terai' (plain land), 'Hilly', and the 'Himalayan' region. The difference in altitude has resulted in differences in climate, vegetation, and variety soil type as well. Furthermore, the formation and constituent of any soil is dependent on the parent materials.

The first soil survey in Nepal dates back to 1965 in Khajura Forest Area (Nepalgunj-Surkhet road) which continued annually up to 1995. The initial report of soil classification in Nepal was generated under Land Resource Mapping Project (LRMP, 1986) which was funded by Canadian International Development Agency (CIDA). It relied on the United States Department Of Agricultural System. The classification represented 14 soil groups and 4 soil orders; Entisols, Inceptisols, Mollisols, Alfisols (other orders: Spodosols, Histosols, Utisols, Aridisols in lesser occurrence).

However, the difficulties and unavailability of uniform methods in classification of soil are the probable reasons for the hindrance of detailed classification of soil in Nepal. Soil Science Division, Nepal Agricultural Research Council (NARC) has been able to conduct soil survey of Terai (20 districts, till 2015) and Hill districts (35 districts, till 2015) of Nepal. It has helped in the development of general inferential guide of soil of those districts.

Soil classification of Nepal

Based on Indigenous Classification System

Farmers of Nepal have developed their own classification system based on soil colour, texture, depth. It is difficult to approach scientifically but directs the potential techniques (Shah, 1995).

Based on USDA (LRMP, 1986)

• Entisols: They mainly occur in riversides and lack clear soil horizon. Fluvents and Orthens are the main groups of Entisols of Nepal.


• Inceptisols: They are the important soil order as most of the agricultural and forestry activities are common on them. Important soil groups include Aquepts, Ochrepts, Umbrepts.


• Spodosols: They occur above 3000 metres and are rarely found. They have the presence of reddish-black subsoil.


• Mollisols: They are found in Terai and western Nepal in calcium-rich parent materials.


• Alfisols: They are present in sloping land or in older alluvium.


• Ultisols: Only one Ultisols - Rhodudult (with low pH and low base saturation) are found in Tars area. They represent the oldest and weathered soils.


• Aridisols: They are found in rain shadow areas of Nepal. They remain dry for more than half a year.

Based on FAO Soil Classification (World Soil Classification)

The tables from Soil and Terrain (SOTER) database for Nepal, Dijkshoorn & Huting, 2009 has been cropped from and pasted from the report.

Five physiographic regions as classified in LRMP study from Dijkshoorn & Huting, 2009

Physiographic regions - Proportion of Nepal -  General elevation (m.a.s.l.) - Description 

 Terai (14 %)  60-330 masl  recent post Pleistocene alluvial deposits forming a piedmont plain 

 Siwaliks (13%)  <1000 masl  semi-consolidated Tertiary sandstone siltstone, shale and conglomerate 

 Middle mountains (30%)  <2500 masl dominantly Precambrian phyllite, quartzite, schist, granite and limestone 

 High mountains (20%) <4000 masl Precambrian metamorphosed gneisses and micaschist 

 High Himalaya (23%)  >3500 masl  dominatly glaciated bedrock surfaces of gneiss, schist, limestone and shale.  

Dominant soils derived from the SOTER database for Nepal based on FAO - UNESCO map of the world, 1988 (Dijkshoorn & Huting, 2009)

As of February 2021, the soil portal has been launched in Nepal (the soil portal being the first among the south asian countries) jointly developed by International Maize and Wheat Improvement Center (CIMMYT) collaboratively with Nepal Agricultural Research Council’s (NARC) National Soil Science Research Center (NSSRC) soilmap.

Conclusion

The soil database helps in identification of potential zones for agriculture. The crop suitability maps helps in country like Nepal with such varied micro climatic zones. The scientists involved in this field have lot to explore, understand the complexities of the topic along with sharing their understanding to others.

Bibliography

• (2010/2011). Annual Report. Soil Science Division,2068. Khumaltar, Nepal: Nepal Agricultural Research Council.


• Dijkshoorn, K., & Huting, J. (2009). Soil and Terrain database for Nepal. 6700 AJ Wageningen: ISRIC, World Soil Information.


• FAO. (1988). Revised Legend of the FAO - UNESCO Soil Map of the World. Rome: International Soil Reference and Information Centre.


• Galbrath, J. M. (2013). Challenges to Sustaining Agriculture. National Cooperative Soil Survey Conference, (pp. 1-46).


• Khadka, Y. G. (2012). Soil Survey, Soil Mapping and Soil Status in Nepal. Regional Conference on the Asian Soil Partnership (pp. 1-37). Nanjing, China: FAO.


• (1986). Land Resource Mapping Project: Summary Report. Kenneth Earth Sciences Limited.


• Secondary Soil Classification and Mapping. (n.d.). Retrieved August 14, 2019, from Soil-net.com


• Shah, P. B. (1995). Indigenous agricultural land and soil classifications. Challenges in Mountain Resource Management in Nepal. Processes, Trends, and Dynamics in Middle Mountain Watershed .


• Shrestha, R. K. (1992). Agroecosystem of the Mid-Hills. In J. B. Abington (Ed.), Sustainable livestock production in the mountain agro-ecosystem of Nepal. FAO.


• Ure, A. M., & Berrow, M. L. (1982). The Elemental Constituents of Soils. In Environmental Chemistry (pp. 94-96). Royal Society Of Chemistry.