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Changes of Some Chemical Properties of Intensively Cultivated Soils of Bangladesh

M. Rahman
Director (Retd,)
SRDI, Dhaka

M. Arshad
Scientific Officers
Central laboratory, SRDI, Dhaka

Abstract/ Executive Summary:

Samples from twenty four soil series collected from intensively cultivated land of four physiographic units of Bangladesh were evaluated in relation to the changes of some chemical properties of soil. The cropping patterns practiced by the farmers and its management have significant impact on some of the chemical properties of soil. The soil pH showed 1-1.4 unit lower than those of earlier samples of Tista Meander floodplain and Piedmont Plain soils. The total nitrogen content increased slightly with corresponding increase in organic matter content. The wet or moist soil condition of 8-9 months for rice-rice mono cropping practice may result in increased accumulation of organic matter from weeds, rice straw and addition of cowdung, green manuring etc. Calcium, magnesium and potassium contents decreased slightly except in Brahmaputra floodplain, which is an indication of soil degradation.

Keywords: Intensively cultivated, Physiographic units, Changes, Chemical properties, Soil

Location: Greater Dinajpur, Rajshahi, Bogra, Pabna, Rangpur, Mymensingh and Gazipur

Start Date:

End Date: 00-00-1998

Program Area: Crop-Soil-Water Management

Commodity: Land degradation

Objectives:

The data in the Thana Land and Soil Resources Utilization Guides give overall nutrient status of Bangladesh soils, but these data do not satisfy the criteria for comparison purposes. To get sufficient evidences of soil degradation of intensively cultivated areas, comparison between two sets of soil analytical data derived from similar places and same method of analysis are required. A comparative study based on this criteria can provide meaningful results. Keeping this in mind, the present study was conducted to evaluate the changes of soil properties of some intensively cultivated lands.

Methodology:

Twenty four representative soil series distributed in four physiographic units of Bangladesh were selected. Among them six were from Tista floodplain, eight from Barind tract, five from old Brahmaputra floodplain and five from Piedmont plain. About 20-25 years ago, most of the main agricultural highlands and medium highlands were under either double or single cropping. In course of time, most of the single cropped land has turned into double or triple cropped and that of double cropped land into triple cropped land. About 25-30 years ago top soils were sampled from 0-10cm depths and the samples were stored. Again in April-May, 1998 top soils at the same depths and from the same places or sampling sites were collected. The samples collected in two distant times were then analyzed by the same analytical methods. Soil pH was determined with glass electrode in a saturation extract. The total nitrogen content was determined by a micro Kjeldahl method. Available phosphorus was determined either by a modified Bray and Kurtz method or Olsen's method depending on soil pH. Exchangeable Ca, Mg, and K were determined by atomic absorption spectrophotometer and flame photometer, using H4OAC extraction. All soil sample were replicated in triplicates and average values were considered.

Source of Information: SRDI 2001. Soil Resources in Bangladesh: Assessment and Utilization. Proceedings of the annual workshop on soil resources. 14-15 February, 2001. SRDI, Dhaka.

Article Link (Online Journal):

Funding Source:

1. Government

Budget: 240000 (approx)

Total Budget (Tk.) : 240000 (approx)

Achievement/Findings:

The study reveals that the changes of cropping pattern, use of fertilizers, irrigation and management practices have had both positive and negative impact on some chemical properties of soils. The positive effect is that although organic matter content is low to medium there is no trend toward a decline, rather a slight increase in some cases. The changes include reduction of soil pH, Ca, Mg, and K contents. The small changes of chemical properties of soils

Knowledge Management: Report/Proceedings