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Structural Attributes of Some Tea Soils of Bangladesh

S. U. AHMED
Department of Soil, Water and Environment, University of Dhaka, Dhaka-1000, Bangladesh

S. M. A. FAIZ
Department of Soil, Water and Environment, University of Dhaka, Dhaka-1000, Bangladesh

T. H. KHAN
Department of Soil, Water and Environment, University of Dhaka, Dhaka-1000, Bangladesh

Abstract/ Executive Summary:

Structural status of the soils was studied in Water divide, Hill slope and Hill foot locations of the hills occupying New Tea Plantation, Old Tea Plantation and Natural Vegetation Texturally the soils were mostly sandy loam and sandy clay loam. The portions of microaggregates were higher with decreasing particle size and larger aggregates were adversely affected in Old Tea Plantation. Most of the clay particles were present in aggregated forms . Considerably higher bulk density was observed in subsurface at Water divide and Hill slope locations for New and Old Tea Plantation and consequently total porosity showed opposite trend. Greater compaction (lesser porosity) in Old Tea Plantation was attributed to continuous cultural operations to a shallow depth during tea cultivation. Microaggregates gave rise to capillary pore spaces and hence air phases were low as compared to solid and liquid phases. In New Tea Plantation, hydraulic conductivity in most of the horizons could be characterized as moderate to rapid, while in Old Tea Plantation and Natural Vegetation it was slow to moderate. Adverse effects of tea plantation with respect to structure, bulk density, pore size distribution, three phase distribution and permeability of the soils were evident.

Keywords: Water divide, Hill slope, Hill foot

Location: Balisera Circle" under Kamalgonj Upazilla, district of Mulvibazar, Bangladesh

Start Date:

End Date:

Program Area: Crop-Soil-Water Management

Commodity: Land degradation

Objectives:

To observe the structural attributes of tea soils, particularly where better tea varieties and increased use of fertilizer failed to increase yield in the long run.

Methodology:

The research area was covered by the soils of "Balisera Circle" under Kamalgonj Upazilla, district of Mulvibazar, Bangladesh. Three hills were selected for the study, one under New Tea Plantation (about 14 years old) and one under Old Tea Plantation (above 65 years old) and another under Natural Vegetation included for comparison . For each of the hills three sites, viz. Water Divide (top), Hill Slope (middle) and Hill Foot were selected for studies. Nine pits were opened up to a depth of 90 cm. Undisturbed core samples and soil samples were collected from different horizons and transported to the laboratory. Hygroscopic soil moisture was determined by method of Black. Soil particle size analyses were made by combination of sieving and hydrometer methods, and textural classes determined by Marashall's Triangular Coordinate Curve as devised by USDA 1951. Bulk density was determined by core method. A core sampler was used to obtain undisturbed core samples of 100 cm³ volume. Microaggregate analysis was carried out following the method of Kachiniski. Soil particle density was determined by pycnometer method. Total soil porosity was calculated from the data of particle density and bulk density. Pore-size distributions were computed from soil moisture retention curves obtained by pressure plate apparatus. Volume percentages of the three phases of the soils were computed from the data of bulk density, particle density and moisture contents at 0 .33 bar tension. Hydraulic conductivity of soils was determined by constant head method .

Source of Information: Dhaka Univ. J. Biol. Sci. 10(2): 151-160, 2001 (July)

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

From the above study it can be concluded that over long years of cultivation the old tea soils have considerable adverse effect on different structural indices of the soils.

Knowledge Management: Journal