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Critical Level of Potassium of Some Representative Bangladesh Soils as Determined by Using Two Different Models.

S. M. Imamul Huq
Department of Soil Science, University of Dhaka, Dhaka 1000, Bangladesh

D. Hassan
Department of Soil Science, University of Dhaka, Dhaka 1000, Bangladesh

A. Islam
Department of Soil Science, University of Dhaka, Dhaka 1000, Bangladesh

Abstract/ Executive Summary:

Soil-potassium of a few widely varying representative Bangladesh soils was assessed by four different extract ants viz., neutral 1N NH₄OAC (K_AA). Agro Services International (ASI) (K_AS), acidified 1M NaCl (KN_aCL) and boiling 1N HNO₃ (K_NA) for wetland rice and upland wheat. The critical levels of potassium in these soils were determined by using the Cate- Nelsen graphical method and the statistical method of Waugh et al. The critical values obtained by these two methods were 0.072 (K_AA), 0.108 (KAS), 0.09(KN_aCl) and 10.66 (KNA) meq% for rice 0.102 (K_AA), 0.126 (K_AS), 0.089 (KN_aCl) and 0.54 (K_NA) meq% for wheat. The values correlated well between the Cate- Nelsen graphical method and the statistical method. On the basis of these values, soils expected to be responsive of potassium fertilization were classified.

Keywords: Soil potassium, Critical level.

Location: The soil series were Chandina, Chandra, Ghatail, Kalma. Khadimnagar, Mirsarai, Noadda, Pirgacha. Ranisankail, Sonatala and Tejgaon soil series, from Bangladesh.

Start Date:

End Date:

Program Area: Crop-Soil-Water Management

Commodity: Fertilizer

Objectives:

To verify the contentions and to re-establish the critical level of soil-K of eleven representative soil series of the country for wetland rice and upland wheat by using four different commonly used extractants and employing two different models.

Methodology:

Eleven representative soil series varying in their parent materials and other properties and supposed to have different potassium contents were included in the present study. The soil series were Chandina. Chandra, Ghatail, Kalma. Khadimnagar, Mirsarai, Noadda, Pirgacha. Ranisankail, Sonatala and Tejgaon. The soil samples were collected at a depth of 0-15 cm from surface at different sites of Bangladesh. Some of the basic properties and general features of the eleven soils are presented. The soil samples were analysed after usual processing for extractable-K by using neutral 1N NH₄OAc. Agro Services International (10) extractant, 1M NaCl acidified to pH 3.0 (11) and boiling 1N HNO₃. The corresponding K-values are designated as K_AA, K_AS, KN_aCl, and K_Na respectively. Pots of 11 size were used in this study. The basal applications of N and P₂O₅ were selected according to the Fertilizer Recommendation Guide on the basis of soil analysis values for N and P. the K-application doses were at the rates of 0, 20, 40, 60, 80, 100, 120 and 140 kg/ha. The sources of N, P and K were urea, TSP and MP respectively. BR22 variety of rice and Kanchan variety of wheat were used as test crops. The rice seedlings the Bangladesh Rice Research Institute (BRRI) while the seeds of wheat were procured from Bangladesh Agricultural research Institute (BARI). There were four replicates in each treatment. The treatments were arranged randomly. The position of the pots were rearranged very alternate day to facilitate equal exposure to sunlight. At the maximum tillering stage the plants were cut at th ground level, cleaned and dried at 80±5^oC for 48th to get the d.m. yield. The critical levels of potassium for the four extractants were determined separately using the models. According to Graphical procedure, relative yield (Y₁/Y₂ × 100, where Y₁ is the yield at no-K, Y₂ is the maximum yield obtained in K –fertilized pot) was calculated for each soil series. A scattered diagram of relative yield versus soil-K test values were plotted on an arithmetic paper. A pair of intersecting perpendicular lines were drawn on the plotted paper in such a way that the line parallel to the X-axis intersected the Y –axis at a relative yield between 75% and 80% (in our case it as 77%) and the line parallel to the Y-axis was drawn in such a way that the number of points in the negative quadrants were the minimum. The intersecting point of this line on the X-axis as considered the “critical” soil –K level. In the Statistical model, relative yield (Y) as calculated as in Cate-Nelson procedure and the values were ordered along with the corresponding soil-K test values. The (X,Y) pairs were maintained in this order throughout the analysis. The R2 values of two groups were calculated by using successive tentative critical levels of two groups. The maximum R2 values obtained for the group as considered the range of critical value. The man of the two classed was predicted critical value.

Source of Information: Manuscript received July 19, 1994 and in revised from August 20, 1994

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

In the present investigation a number of critical level values for soil-K as extracted by different extract ants have been found for wetland rice and upland wheat crops. It has also been observed that the values for critical level of soil-K for KAA and KAS for wheat are higher than that found for wetland rice. These values can effectively be used to differentiate soils as to the K-responsiveness from K non-responsiveness. It indicates that crop yield will respond strongly to applied K on those soils here the extractable-K level is very close to or below the critical level observed and be of great help in a rational K-fertilization program for crops. Accordingly, all soils except Ghatail, Kalma and Noadda fall in the K-responsive category.

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