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Moisture Properties of Some Tea Soils of Bangladesh

S. U. AHMED
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

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

Abstract/ Executive Summary:

Moisture properties of the soils were 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. Moisture properties of the soils expressed in terms of "soil moisture retention curves" in which volume percentage of water has been plotted against the metric suction of the soils. The rate of decrease in moisture. content with increasing metric suction varied within narrow limits for different soils as was indicated by the slope of the moisture retention curves . Most of the stored water in the soils was released by tension between pF 3.0 and 3.5. Therefore, lower amount of moisture was released for further increase in tension from pF 3.5 to 4.2. In Hill Foot profile under New Tea Plantation and Water Divide under Old Tea Plantation, all horizons remained near saturation up to pF 2.0. It was revealed that these two soil profiles were devoid of freely drained large pores and were more compact. In all other horizons of soil profiles from different hills, volumetric moisture contents of the soils decreased almost linearly with metric suction applied to the soil up to pF 3.0. Maximum water holding capacity was slightly higher in the two tea plantation hills (58.3%) than the natural vegetation hill (< 55.1 %). Moisture equivalent was very close to field capacity and showed similar trend in their change with depth of the profiles. Wilting points were considerably higher in soils of Old Tea Plantation, followed by Natural Vegetation and then New Tea Plantation. The content of capillary water was considerably higher in soils of Natural Vegetation as compared to other two hills. Correlation studies were made between soil moisture properties and various soil parameters. Organic matter and structural indices showed considerable influence on the moisture properties of the soils.

Keywords: Water Divide, Hill Slope, Hill Foot, Moisture properties, Tea soils

Location: Balisera Circle under Kamalganj Upazilla in the district of Moulvibazar

Start Date:

End Date:

Program Area: Crop-Soil-Water Management

Commodity: Land management

Objectives:

To study the moisture properties of tea soils of Bangladesh.

Methodology:

The research area was located at Balisera Circle under Kamalganj Upazilla in the district of Moulvibazar. Three hills were selected for study, one under New Tea Plantation (about 14 years old), one under Old Tea Plantation (about 65 years old) and a hill under Natural Vegetation 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 transplanted to the laboratory. Organic carbon was determined by wet-oxidation method and organic matter was calculated by multiplying the values of organic carbon with 1.724. Analyses of soil particle size were made by combination of sieving and hydrometer methods, textural classes were determined by Marshall's Triangular Coordinate Curve as devised by USDA (1951). A core sampler was used to obtain undisturbed core samples of 100 cm³ .m Bulk density was determined by core method. Microaggregate analysis was carried out by the method of Kachinisky. Soil particle density was determined by pycnometer method. Total soil porosity was calculated from the data of particle- and bulk density. Water- and air porosity of the soils were computed from the data of bulk density, particle density and moisture contents at 0.33 bar tension. Hygroscopic soil moisture was determined by method of Black. Hydraulic conductivity of soils was determined by constant head method. Soil moisture contents at 0 - 1.0 bar were determined on undisturbed core samples, while moisture contents at 3.0 to 15.0 bars were determined on disturbed, ground and sieved samples. For tension between 0.1and 15.0 bars, the pressure plate apparatus was used as described by Richards.

Source of Information: Dhaka Univ. J. Bio.. Sci. 15(1): 1-10, 2006 (January)

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Most of the stored water in the soils was released by tension between pF 3.0 and 3.5. Therefore, lower amount of moisture was released for further increase in tension from pF 3.5 to 4.2. In Hill Foot profile under New Tea Plantation and Water Divide under Old Tea Plantation, all horizons remained near saturation up to pF 2.0. It was revealed that these two soil profiles were devoid of freely drained large pores and were more compact. In all other horizons of soil profiles from different hills, volumetric moisture contents of the soils decreased almost linearly with metric suction applied to the soil up to pF 3.0. Maximum water holding capacity was slightly higher in the two tea plantation hills (58.3%) than the natural vegetation hill (< 55.1%).

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