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Structural Attributes of Soil Under Rice-based Cropping Pattern in the Ganges-kobadak Project Area of Bangladesh.

M. H. Rahman
Department of Soil Science, Dhaka University , Dhaka.

T. H. Khan
Department of Soil Science, Dhaka University , Dhaka.

S. Hoque
Department of Soil Science, Dhaka University , Dhaka.

Abstract/ Executive Summary:

Soils of the investigated areas were dominated by silt fraction and the coarse sand fraction was almost absent iri all the soils. Irrigation and accompanying management practices d id not have any influence on particle size distribution. Indexes of aggregation (both state and degree) did not show any definite trend in their variation with the depth of the horizons in a given profile, but showed a good relationship with topographic position of the profiles in the catena in all the three locations. The values of soil bulk density were lower in the Ap1 horizons compared to the values in the Ap2 horizons and consequently total porosity showed opposite trend. These results indicated the formation of compact plow sole at the shallow depths of the soils. Plow soles were more prominent in the irrigated areas. M ost of the horizons of the different soil profiles were medium compact to compact. Total porosity of the Ap2 horizons in most of the soil profiles are unsatisfactory for dry land crops. Ap1 and Ap2 horizons q.f all the soil profiles lake in air porosity which may create constraints in the cultivation of upland crops. In Sara series hydraulic conductivity in most of the horizons could be characterized as moderately slow to moderate, while in Gopalpur and Ishurdi series it was slow to moderately slow.Correlation studies showed that structural attributes showed significant correlations with organic matter, clay, silt and sand contents of the soils.

Keywords: Land management, Soil, Soil nutrient, Soil parameters

Location: Sara, Gopalpur and lshurdi soil resires, Bangladesh

Start Date:

End Date:

Program Area: Crop-Soil-Water Management

Commodity: Land management, Rice

Objectives:

To investigate the structure and structural attributes of the soils under study, some physical and chemical parameters of the soils.

Methodology:

Three major soil series covering vast areas of the G. K. Project and occurring In the same catena were selected for the study. These include Sara. Gopalpur and lshurdi. In order to evaluate the Influence, if any of embankment. Irrigation and related soil management practices on structure and structural attributes of the soils. At each of the elected sites pits were opened and undisturbed core samples (in triplicate) and disturbed soil samples were collected from each of the genetic horizons upto a depth of 120 cm. The core samples were placed in wooden box and disturbed samples were put into polythene bags for transportation to the laboratory.Prior to laboratory analyses, the disturbed soil samples were airdried, ground and screened to pass through 2.0 mm sieve for particle size analysis and a separate airdried soil sample was passed through 0.25 mm sieve for chemical analysis. A small portion from each of the ungrounded soil samples was preserved for micro-aggregate analysis. Soil organic matter was estimated from organic carbon, determined wet oxidation method. Free carbonates were determined by rapid titration method. Ferrous and ferric iron contents of the fresh moist soil samples were determined. Particle size analysis of the soils was made by a combination of sieving and hydrometer methods as described, and textural classes were determined by Marshal l's Triangular Coordinate. Micro aggregate analysis was carried out with the exception that a combination of sieving and hydrometer methods were used to determine the particle size distribution instead of pipette method. Bulk density was determined by core method. A Daiki Core Sampler was used to obtain undisturbed core samples of 100 cm 3 volume. Particle density of the soils was determined by pyrometer. Total 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, parllcle density and moisture contents at 0.33 bar tension. Hydraulic conductivity was determined in the laboratory on undisturbed core samples by constant head method.

Source of Information: Bangladesh J. Soil Sci. 23 (1&2), 79 - 91, 1992, ISSN 0253-5440

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

These results indicated the formation of compact plow sole at the shallow depths of the soils. Plow soles were more prominent in the irrigated areas. Most of the horizons of the different soil profiles were medium compact to compact. Total porosity of the Ap2 horizons in most of the soil profiles are unsatisfactory for dryland crops. Ap1 and Ap2 horizons of all the soil profiles lack in air porosity which may create constraints in the cultivation of upland crops. In Sara series hydraulic conductivity in most of the horizons could be characterised as moderately slow to moderate, while in Gopalpur and Ishurdi series it was slow to moderately slow.Correlation studies showed that structural attributes showed significant correlations VJith organic matter, clay, silt and sand contents of the soils.It can be concluded that no noticeable change was observed in the structural attributes of these soils due to variations of Irrigation and management partices.

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