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Determination of Critical Level of Soil K for Wetland Rice

M. O. Haque
Bangladesh Institute of Nuclear Agriculture, Mymensingh.

M.I. Ali
Bangladesh Institute of Nuclear Agriculture, Mymensingh.

A. Islam
Professor
Dept of soil Science, University of Dhaka.

S. Hoque
Assistant Professor
Dept of soil Science, University of Dhaka.

Abstract/ Executive Summary:

A pot culture experiment was conducted in the greenhouse with 20 selected soils of Bangladesh to determine the critical level of soil K for wetland rice. The soils were analyzed for their K status by 1N NH₄OAc, ASI, and 1.4 NH₂SO₄ extraction methods. The soils showed K status from low to high and the crop responded to K application particularly where the exchangeable K level was low. The relationships between the extraction methods were highly significant. The calibration of soil-test K values with relative yields of rice showed the critical levels of soil K at 0.11, 0.105 and 0.155 me% for NH₄OAc, ASI andH₂SO₄ method, respectively.

Keywords: Determination, Critical level, Soil K, Wetland rice

Location: Greenhouse,BINA, Mymensingh

Start Date:

End Date:

Program Area: Crop-Soil-Water Management

Commodity: Manures

Objectives:

To determine the critical level of soil K for wetland rice.

Methodology:

A pot culture experiment was conducted in the greenhouse to determine the critical level of soil K tor wetland rice by neutral 1N NH₄OAC (Pratt, 1965), 1.4N H₂SO₄ (Hunter and Pratt, 1957) and AS1 (Hunter, 1984) extraction method. Twenty soils representing 20 different soil series of Bangladesh were used for this study . Each soil received three treatments viz. (i) all nutrients (NPSZn) minus K (ii) all nutrients (NPSZn) plus 100 ppm K and (iii) all nutrients (NPSZn) plus 200 ppm K. The source of K was KCl (Analar grade). The experiment was laid out in a completely randomized block design with three replications of each treatment. An amount of 2 kg air dry soil was taken into each plastic pot and moistened with distilled water. Sprouted seeds of rice ( BR14 ) were sown in each pot and after establishment 12 seeds were allowed to grow until six weeks of age. Cultural operations including watering with distilled water, weeding mulching etc. were done as per requirements. After harvesting plants were dried, in an oven at 65⁰C to keep the record of dry matter yield. Soil samples were collected from a depth of 0-15 cm. The samples were air dried and ground to pass through a 2 mm sieve. The samples were analyzed for 1.0N NH₄OAC, AS1 and 1.4N H₂SO₄ extractable K. The ASI extractable K was measured following the method of Hunter (1984). The extracting solution was 0.25N NaHCO₃-0.01 M EDTA-O.01N NH₄F with 5 gm superfloc 127 per 10 litre, the soil-extractant ratio being 1 : 10 and shaking time 10 minutes. The critical levels of K for the NH₄OAC, ASI and H₂SO₄ methods were determined separately using the procedure developed by Cate and Nelson (1965). Accordingly the relative yield (known as Bray's per cent yield) was calculated from the following relationship. % relative yield =[(Yield without K)/(Yield with K)}×100.

Source of Information: Bangladesh J. crop sci. 1991, 2 (1) : 93-100

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The soils showed K status from low to high and the crop responded to K application particularly where the exchangeable K level was low. The relationships between the extraction methods were highly significant. The calibration of soil-test K values with relative yields of rice showed the critical levels of soil K at 0.11, 0.105 and 0.155 me% for NH₄OAc, ASI andH₂SO₄method, respectively.

Knowledge Management: Journal