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Degradation of Soil Physical Properties in Six Soil Series of Chakaria Sundarbans Mangrove Forest in Bangladesh

Md. Razib Rahman
Soil Resource Development Institute, Farmgate, Dhaka, Bangladrsh

Abstract/ Executive Summary:

A comparative semi-detailed soil survey was made during January to July 2012 to assess the impact of deforestation on changing soil chemical in six soil series of Chakaria Sundarbans mangrove forest since 1973. This study intended to determine the type and quantity of soil degradation and their causes. Among the physical degradations, clay migration and compactness in the surface horizon have been studied. Soil profiles are described in the field following USDA Soil Taxonomy. Soil physical analyses have been made following conventional soil analysis methods and as followed during Reconnaissance Soil Survey (RSS) carried out in 1973. Six identified soil series viz., Badarkhali, Barabakia, Chakaria, Cheringa, Kutubdia & Pahartali have been considered for the study. A considerable variation was observed in the sand, silt and clay distribution of the different soil series sampled in 1973 and 2012 in the study area. The clay content showed lower values for most of the soil series sampled in 2012. Since Clay migration from the top soil observed almost in every soil series it indicates the degradation of soil quality.

Keywords: Soil Physical Properties, Degradation of Soil, Six Soil Series and Chakaria Sundarbans Mangrove Forest.

Location: Chakaria Sundarbans, a deforested area of Cox`s Bazar district of Bangladesh.

Start Date: 01-01-2012

End Date: 31-07-2012

Program Area: Crop-Soil-Water Management

Commodity: Land degradation

Objectives:

To determine the type and quantity of soil degradation and their causes.

Methodology:

The study has been conducted in Chakaria Sundarbans, a deforested area of Cox`s Bazar district of Bangladesh. It lies in the delta of Matamuhuri River of Cox’s Bazar district. Soil samples were collected from Badarkhali soil series; Barabakia soil series; Chakaria soil series; Cheringa soil series; Kutubdia soil series; and Pahartali soil series. To conduct a detail soil survey of the study area the base material e.g. topographic map, Reconnaissance Soil Survey (RSS) maps and reports, aerial photographs, Upazila Land & Soil Resources Guide (Upazila Nirdeshika) and other related study reports have been collected. The basis of the soil survey was air photo interpretation supported by a planned program of field traverses, which has done in 1973 during reconnaissance soil survey of SRDI. The other basis was laboratory analysis of representative soil samples of selected series that were collected from the same sites indicated in RSS report, 1973.Remote sensing technology has been used during survey. The data sources were social survey, field measurement, and topographic map and Land sat TM images. Geometric correction was performed with bilinear transformation and the root mean square error was (0.49) controlled within less than one pixel for 42 ground control points (GCPs). Soils were examined as often as necessary along these traverses. Selected profiles were described from pits dug along traverses, supplemented by spot identification from auger holes. Routine traverse examinations were made to a depth of 120 cm and profile pits for detailed description and sampling of the representative soils were examined to a depth of about 180 cm or more. Pits have been excavated both on RSS sites and catena basis and profile has been described to study the soil morphology of the study area. Morphological and physical studies such as horizon boundary, texture, structure, color, effective depth of soil, concretion, porosity, consistence etc. of each horizon/layer for every differentiate soils have been described. Correlations for soil series identification have been followed by the USDA soil taxonomy. The nomenclature of FAO, as described in the booklet “Guideline for Soil Description” which is essentially derived from the USDA Handbook 18, the Soil Survey Manual has been followed. Color notation has described according to the Munsell Soil Color Chart (Munsell Color Company). The main soil unit recognized was the soil series during RSS done by SRDI. Wherever soils with similar properties occur in the survey area and elsewhere, they are called by the same name. Air-dried soil samples previously ground and passed through a 2 mm sieve were used for the analysis of the particle size distribution. Analysis of the particle size distribution was carried by the pipette sampling method as outlined by Gee and Bauder. Analysis of the soil samples of individual horizon of each profile was carried out as mentioned above. The analytical observation was weighed with the thickness of each horizon and summed up to the 0-15 cm, 15-30 cm, 30-100 cm and 0-100 cm layers to eliminate the error associated with the differences in sampling depths as reported earlier.

Source of Information: BANGLADESH RESEARCH PUBLICATIONS JOURNAL ISSN: 1998-2003, Volume: 10, Issue: 4, Page: 345-350, January - February, 2015

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Remarkable changes in land use practices and soil characteristics were observed during the period, 1973-2012 due to deforestation of the mangrove. Over the periods of time, soil characters underwent changes as a result of climate, geology, changes in land use patterns and faster decomposition of organic matter in the soil ecosystem. The change in land use negatively affects physical and chemical properties of soils of the study area. Clay migration from the top soil observed almost in every soil series. Decrease in clay content in top soil of Badarkhali, Chakaria and Pahartali soil series was also observed markedly. Soil management practices, however, have not kept pace with these changes especially in the point of agricultural production.

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