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Characterization of Khagrachhari Hill Soils (dystric Eutrochrept) for Phosphorus Sorption and Phosphorus Saturation

Thaingpru Marma
MS student
Department of Soil Science, Patuakhali Science and Technology University, Dumki, Patuakhali-8602, Bangladesh

Dr. Md. Fazlul Hoque
Professor and Research supervisor
Department of Soil Science, Patuakhali Science and Technology University, Dumki, Patuakhali-8602, Bangladesh

Abstract/ Executive Summary:

Increasing cost chemical phosphatic fertilizer limits its use in developing countries while over dose of P is a problem for eutrophiocation in the developed part of the world. The present study involves the characterization of soil samples collected from Mahalchori Upazilla under Khagrachori district for maximum P sorption capacity, energy of adsorption, buffering capacity of P and P saturation. The Langmuir adsorption isotherm was found well to explain the P adsorption in most of the soil samples where coefficient of determination (R²) value ranged from 0.5544 to 0.9217. The Freundlich adsorption isotherms were also fitted well in the studied soils. The Freundlich adsorption isotherm (R² value varied from 0.9140 to 0.9989) fitted well in the studied soils than the Temkin adsorption isotherm (R² value ranged from 0.7063 to 0.9686). Maximum phosphorus adsorption capacity (MPAC) of different soil samples varied from 1112 to 1999 mg kg^-1. Soil 5 showed the highest value of MPAC (1999 mg kg^-1) and soil 4 showed the lowest value (1112 mg kg^-1). Energy of adsorption varied from 0.16 to 1.28 µg ml^{– 1}. Soil 4 had the highest (1.28 µg ml^-1) energy of adsorption and soil 5 had the lowest energy of adsorption of 0.16 µg ml^-¹. The range of P buffering capacity was varied from 131.87 to 298.98. Soil 2 showed the highest buffering capacity (298.98) and soil 4 showed the lowest (131.87). The P saturation (P_sat) of different soils varied from 0.06 to 0.62 µmol g^-1. The highest (0.62 µmol g^-1) value of P_sat was observed in soil 1 and the lowest (0.06 µmol g^-1) was in soil 3. Phosphorus sorption characteristics of soil seems to closer look for P management and these are necessary components in the interpretation of soil test values as well as for making specific fertilizer recommendations across soil types.

Keywords: Phosphorus sorption capacity, Energy adsorption, Buffering capacity, P saturation

Location: Department of Soil Science, Patuakhali Science and Technology University, Dumki, Patuakhali

Start Date: 00-03-2013

End Date: 00-04-2013

Program Area: Crop-Soil-Water Management

Commodity: Land management

Objectives:

To determine phosphorus sorption characteristics of selected hill soils.
To assess phosphorus saturation condition of the selected hill soils.

Methodology:

Sampling site and sample collection

The laboratory experiment conducted at the Department of Soil Science, Patuakhali Science and Technology University, Dumki, Patuakhali during March to April 2013 involves five surface (0-15cm) soil samples collected from farmer’s cultivated rice fields during January to February 2013 after T-Amon harvest. The selected soil sampling site includes two unions of Mahalchari and Sindhukchari of Mahalchari Upazilla under Khagrachari district. The collected samples were air dried, ground to pass through a 2-mm sieve and then mixed to from a composite sample.

Phosphorus sorption isotherm studies were followed the procedure of Nair et al. (1984). Briefly, one gram of the soil sample was taken in 25 ml test-tube with various addition of P (0, 1, 3, 6, 12, 18, 30, 48 and 60 ppm) in 20 ml of 0.01M CaCl₂solutions separately. The resultant P content was 0, 20, 60, 120, 240, 360, 600, 960 and 1200 mg kg^-1. Then the test tubes were shaken for 24 hrs on horizontal shaker with low oscillation. After equilibration, the supernatant was passed through a Whatman # 42 filter paper and the filtrate was analyzed for P following Murphy and Riley (1962) method. At the same time pH was determined from the aliquot. Sorbed P was inferred from the difference between the concentration of soluble P added in the initial solution and the concentration of P in the solution at equilibrium. The equilibrium P concentration data were interpreted by Langmuir, Freundlich and Temkin Equations.

Phosphorus saturation (P_sat), offered by Sharpley (1995), was estimated by Mehlich-3 (M3) extractable P (Mehlich, 1984). Adsorption maxima (S_max) and the energy of adsorption were estimated from Langmuir P adsorption isotherm. The P-buffering capacity of soils has been calculated from the Temkin equation (Eq. 3), where b is considered the P-buffering capacity.

Source of Information: MS Thesis

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Given the diversity in properties, the studied soil samples were different in the P sorption capacity, energy of adsorption, P buffering capacity and P saturation. There is a variation in the P sorption characteristics in the soil samples collected from different locations of Mahalchori Upazilla of Khagrachori district of Bangladesh. These variations in the P sorption characteristics in soils collected from the different locations seem to closer look of the soil for P management. Phosphorus sorption parameters in soil need to be taken into account in determining P recommendation in hill soils for efficient phosphorus management practices for crop production.

Knowledge Management: Thesis