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Forms of Potassium in Some Soils of Bangladesh

S. A. Chowdhury
Department of Soil Sciences, University of Dhaka, Dhaka-1000, Bangladesh

A. Islam
Department of Soil Sciences, University of Dhaka, Dhaka-1000, Bangladesh

R Mandal
Department of Soil Sciences, University of Dhaka, Dhaka-1000, Bangladesh

S. Hoque
Department of Soil Sciences, University of Dhaka, Dhaka-1000, Bangladesh

S. Rahman
Department of Soil Sciences, University of Dhaka, Dhaka-1000, Bangladesh

Abstract/ Executive Summary:

Fractions of potassium were determined from 29 soils of Bangladesh. A significant variation was observed in relative proportions of water-soluble K, readily exchangeable K, difficultly exchangeable K, lattice K and relatively inert K ranging from 5.1-93.2, 8-189, 119-2465, 330-3776 and 9200-28600 µg g^-1 soil, respectively. Alluvial soils were generally rich in readily exchangeable K and were significantly associated with clay content of the soils. Difficultly exchangeable K was significantly related to CEC of the soils, indicating the presence of some adsorbed K in inert-lattice structure. The results suggest that the soils have good reserve of K to replenish the depletion of readily exchangeable and water-soluble k.

Keywords: Forms of potassium, Exchangable K, Soils of Bangladesh

Location: Dhaka University

Start Date:

End Date:

Program Area: Knowledge Management

Commodity: Fertilizer

Objectives:

To understand the potassium supplying capacity of the soils for plants.

Methodology:

Surface soils (0-15 cm) were collected from 29 representative soil series of Bangladesh. The samples were air-dried, ground and passed through 2 mm sieve for particle size analysis and 0.5 mm sieve for chemical analyses. Particle-size determination were made by using the hydrometer method and pH was determined electrochemically using a combined glass/calomel electrode with a soil : water ratio of 1 : 2.5. Organic carbon was estimated by wet oxidation method (Walkely and Black 1934) and CEC by using 1N ammonium acetate (pH 7.0). Water, 1N NH₄OAc (pH 7.0) and 1N HNO₃ and concentrated HCl were used to extract different fractions of potassium. The soil extractant ratio was 1 : 10 and the period of extraction was 1 h. In case of 1N HNO3 extraction the acid and soil mixture was allowed to stand for 15 min and then boiled for 10 min followed by neutralization with NH₄OH solution (Pratt 1951). Total potassium was extracted by HF-HClO₄ digestion (Pratt1951). Potassium in the extract was measured flame photometrically using a Gallenkamp Flame Photometer. Corrections mentioned below were made for different fractions of potassium : (i) Soluble K: Water extractable K (Kw), (ii) Readily exchangeable K (Krex): 1N NH₄OAc extractable K - Kw, (iii) Difficultly exchangeable K (Kdex): 1N HNO₃ extractable K – 1N NH₄OAc extractable K, (iv) Lattice K (KI): Concentrated HCl extractable K – 1N HNO₃extractable K and (v) Relatively inert K (Ki): HF-HClO₄ digestible K-concentrated HCl extractable K.

Source of Information: Bangladesj J. Sci. Res. 10 (1): 1-8, 1992 (June)

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The results suggest that the soils have good reserve of K to replenish the depletion of readily exchangeable and water-soluble K.

Knowledge Management: Journal