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A Study of Pedological and Edaphological Aspects of the Manpura Island in Coastal Area of Bangladesh

A. Begum
Soil Science Discipline, Khulna University, Khulna, Bangladesh

M. S. Hussain
Member UGC, Agargaon, Sher-e-Banglanagar, Dhaka, Bangladesh.

S. M. Ullah
Department of Soil, Water and Environment, University of Dhaka, Bangladesh.

Abstract/ Executive Summary:

A study was conducted to find out the pedological and edaphological aspects of Manpura island during December, 1994. Five soil profiles were studied from the selected locations of the Manpura island for pedological aspects. Texture of the soils of Manpura is predominantly loamy with an average content of 51% silt and 21% clay and are very productive with mild alkaline reactions. Sand/silt ratio remains more 01, less constant with depth which indicates the uniform nature of parent materials, although there are signs of stratification. Seasonal salinity remains a problem which limits possible growth of crops all the year round. Manpura posses some peculiar environmental characteristics. This island constitutes a part of the active Ganges delta and is gradually changing by sediment accretion and erosion every year. As a result its exact area estimation is difficult. Natural environment is terribly fragile as the banks of this island are still unstable and erosion is a constant threat that may finally result in the obliteration of the island. Climatic type is humid tropical monsoon with sometimes heavy torrential downpour. The island is flat and its elevation varies from place to place from the mean sea level and a large part of the island is flooded twice daily during the high tides in the monsoon season. If global warming causes the sea level to rise, as some people predict, the Manpura island will go under water possibly. Nevertheless, around 50,000 people have already settled there with threat in mind. Rice cultivation is the main occupation of the islanders with fishing and cattle/buffalo farming as secondary activities. The settled pans of the islands are protected from saline water intrusion by dykes. Plantation mangrove forest covers a sizeable part of the island that protects it from the hazards of tropical cyclonic storms and lethal tidal water surges. In spite of the existing ecological hazards the island acts as a source of hope for many poor and landless people of Bangladesh especially those who were made destitute by river bank erosion in the coastal belt.

Keywords: Pedology, Edllphology, Soil, Mnnpura island

Location: Department of Soil, Water and Environment, University of Dhaka, Bangladesh.

Start Date:

End Date:

Program Area: Crop-Soil-Water Management

Commodity: Land development productivity

Objectives:

Objective of this study was to assess the present environmental conditions of this island in the light of its existing soil properties and their future development possibilities.

Methodology:

The study was conducted both in the laboratory and in the field conditions. The materials used and the methods followed in this study have been described here briefly. Edaphological study: The edaphological study was done by collecting information available through interviews with different local and official peoples. Some data were collected from SRDI Staff (2001). The study covered the surrounding environmental features and present land use were included in the study. Information on the geological formation of this island are available in the works of Pramanik (1989); Rahman (1989); Hossain and McConchie (1994). Properties of some soils of Manpura Island were studied by (Begum et al., 2004). Very few studies dealing with the natural calamities of these offshore islands, location and environmental peculiarities and resource management possibilities have been reported (Warrick and Ahmed, 1996). Pedological study: Five soil profiles were studied from the selected locations of the Manpura island. Three soil profiles were collected from paddy fields and two from plantation mangrove forest areas of about 16 years old where keora was the major species. The soil sampling sites were selected in such a way that they represent the different major ecological conditions of Manpura island. For understanding the detailed soil properties, the soil profiles were studied and described in the field according to USDA system (Soil Survey Staff,1951). The collected soil samples were physically and chemically analyzed in the laboratories of the department of Soil, Water and Environment, University of Dhaka. The following standard laboratory determinations were performed on all horizons. Before particle size analysis, organic matter in the soils was removed by treating them with hydrogen peroxide. The soils were dispersed with sodium hexametaphosphate. Particle size distribution analysis of soils was carried out by hydrometer method (Day. 1965). Textural class of soils were determined by Marshall's Triangular coordinate as devised by USDA (1951). pH, available nitrogen and available p of soils were determined as described by Jackson (1967). Available K was determined as described by Black (1965). Organic carbon was measured by wet oxidation procedure of Walkley and Black (1934). The Organic matter content of the soil was determined by multiplying the percentage of organic carbon with conventional Van-Bemelens factors of 1.724. Cation Exchange Capacity (CEC) was measured with 1N ammonium acetate solution at pH 7.0 after 12-hr extraction (Jackson, 1967), The exchangeable cations were determined from NH₄0Ac (pH 7.0) extract as described by Jackson (1967). Ca⁺⁺ and Mg⁺⁺ were determined by atomic absorption spectrophotometer and K⁺ and Na⁺ was determined using flame photometer. Free oxides of iron and manganese were extracted by sodium dithionite according to the method of Kilmer (1960) and were determined by atomic absorption spectrophotometer.

Source of Information: South Asian J. Agric., 2006,1(2): 84-91, ISSN 1991-0037

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The soils of the island as a whole have been characterized as Hydromorphic meaning thereby that they have been formed under an aquic moisture regime. In these hydromorphic soils, the pedogenic process is controlled chiefly by the hydrologic elements and soils usually have developed a mottled layer at the top and a gleyed layer at the bottom. Plantation mangrove forest covers a sizeable part of the island that protects it from the hazards of tropical cyclonic storms and lethal tidal water surges. In spite of the existing ecological hazards the island acts as a source of hope for many poor and landless people of Bangladesh especially those who were made destitute by river bank erosion in the coastal belt.

Knowledge Management: Journal