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Potassium Status of Four Rice Growing Soils of Bangladesh

M. S. Uddin
Asst. Professor, Department of Agriculture Govt. V. M. Coliege, Saturia, Manikgonj,

M. J. Abedin Mian
Professor
Dept. of Soil Science, Bangladesh Agricultural University, Mymensingh.

M. R. Islam
Professor
Dept. of Soil Science, Bangladesh Agricultural University, Mymensingh.

M. A. Saleque
Principal Scientific Officer
Soil Science Division, Bangladesh Rice Research Institute, Joydebpur, Gazipur.

M. S. Islam
DD, BADC farm, Madhupur, Tangail, Bangladesh.

Abstract/ Executive Summary:

Soils of varying K status were selected at the BAU farm, Mymensingh and BADC farm, Madhupur for conducting laboratory, pot, and field experiments to see the dynamics of potassium in wet land rice soils. The soils were BAU-1(0.087 cmol/kg soil), BAU-2 (0.146 cmol/kg soil), Maddhupur-1 soil (0.097 cmol/kg soil), and Madhupur-2 soil (0.706 cmol/kg soil). Almost neutral silt loam soils (Sonatola series) of BAU firm developed on the recent alluvial deposits of Old Brahmaputra Flood Plain and the acidic clayey soils (Noadda and Kalma series) of BADC farm developed on Madhupur clay. The laboratory experiments were potassium release capacity of soils, Q/I relationships of potassium. Results of the experiments showed that BADC farm soils released more K than BAU farm soils. The Q/I relationship showed that the equilibrium exchangeable K (EK₀ ) and labile K (K_L ) of Madhupur-2 soil were higher than other soils. The potential buffering capacity (PBC^K ) was higher in BAU-2 (5.19±0.12 cmol/kg (mol/L)^1/2 soil followed by BAU-1 (4.07±0.09 cmol/kg (mol/L)^1/2 ) and then Madhupur-2 soil (2.23±0.04 cmol/kg (mol/L)^1/2 ). BAU farm soils adsorbed 55 to 60% of added K in non-exchangeable form, while it was 33 to 39% in BADC farm soils.

Keywords: K-release, Soils, Buffering capacity, Relationship

Location: BAU farm, Mymensingh and BADC farm, Madhupur

Start Date:

End Date:

Program Area: Crop-Soil-Water Management

Commodity: Rice, Fertilizer

Objectives:

To determine the K release capacity of soils and to know the Q/I relationship of K for soils.

Methodology:

For this study, soils were collected from two locations, namely BAU farm, Mymensingh and BADC farm, Madhupur. Each location having two soils depending on their initial K status. These soils were BAU-1(0.087 cmol K/kg soil), BAU-2 (0.146 cmol K/kg soil), Madhupur-l (0.097 cmol K/kg soil), and Madhupur-2 (0.706 cmol K/kg soil) soils. A portion of 500 g of each soil was treated with K at the rate of 50 mg K/kg soils from KC1, while another portion of 500 g soil was kept as control. Ten g of treated soil sample (previous) was taken in centrifuge tube in triplicate. Thirty mL of 1.0 M NH₄OAC solution was added to the soil, shaken for 30 minutes and then centrifuged for 10 minutes. After centrifugation, the aliquot was collected for K determination. The whole process was repeated for 10 times. Potassium Q/I isotherms were constructed according to the modified procedure of Beckett described. Soil samples of 2.5 g were placed in 30 ml. centrifuge tube (pre-weighed) containing 25 mL of 0.01M CaCl₂ solutions with KNO₃ concentrations of 0.0, 0.5, 1.0, 2.0, 3.5, and 5.0 mM. The prepared soil suspensions were shaken for 30 minutes allowed to equilibrate for 18 hrs and centrifuged. The supernatant solutions were collected and analyzed for K, Ca, Mg, and Na. After collection of supernatant solutions, the weight of each centrifuge tube with the remaining soil was recorded. Twenty five milliliter of 1.0 M NH₄OAC was added to each centrifuge tube, again shaked (30 minutes), centrifuged (10 minutes), and filtered. The concentration of K, Ca, and Na in the filtrate was determined by flame photometer and the concentration of Mg was determined by atomic absorption spectrophotometer (AAS). The final exchangeable K (EK_f ) for each equilibrium point was calculated based on 1.0 M NH₄OAC extraction at the end of contact of CaCI₂ with correction of interstitial solutions remaining in centrifuge tubes from weight differences. Where ?K is the change of K in solution, CK_i and CK_f are the initial (K concentrated added) and final equilibrium concentration K in solution, whereas v and w are the solution volume and soil mass, respectively. Positive ?K values indicate K adsorption by the soil solid phase whereas negative values indicate K release from the soil phase into solution.

Source of Information: Bangladesh J. Agril. Res. 36(4): 633-646, December 2011, ISSN 0258-7122

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

BADC farm soil released more K than BAU farm soil. In BAU farm, 55-60% added K converted in non-exchangeable form, while it was 33-39% in BADC farm. BAU farm soil exhibited more buffering capacity than BADC farm soil. So, BADC farm soils need more fertilization than BAU farm.

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