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Effects of Mercury on Some Growth Parameters of Rice (oryza Sativa L.)

M.G. Kibria
Professor
Department of Soil Science, University of Chittagong, Chittagong 4331, Bangladesh. Email; kibriactgu @gmail.com

Abstract/ Executive Summary:

Rice (Oryza sativa L.) was grown in earthen pots containing soils of three different textures (clay loam, sandy clay loam and sandy loam) and treated with different levels of mercury (0.00, 0.25, 0.50, 1.00, 1.50 and 2.00 mg Hg kg-1 soil). Crop performance as observed from plant height, number of tiller, number of panicle/ pot and yield among the three soils was better in the clay loam soil and poorer in the sandy loam soil. In general, there was a decrease in plant height with increasing application of Hg in soil. Significantly lower tiller formation from the control treatment in clay loam and sandy clay loam soil started at 1.50 and 1.00 mg Hg kg-1 soil treatment, respectively. The number of panicles was reduced by 8, 20, 18 % with the highest Hg treatment from the control in clay loam and sandy clay loam and sandy loam soil respectively. The number of unifilled grains/panicle showed the opposite trend of change to that of grains/panicle, the highest being observed with the highest rate of Hg application. Grain yield gradually decreased from control to the highest rate of Hg application indicating unfavorable effects of Hg on grain filling process.

Keywords: Mercury, Rice, Tiller, Panicle, Grain, Straw.

Location: Chittagong University

Start Date:

End Date:

Program Area: Crop-Soil-Water Management

Commodity: Rice

Objectives:

To investigate the effects of mercury on growth and yield of rice.

Methodology:

A pot experiment was conducted to investigate the effects of Hg on some growth parameters of rice plant. Rice was grown on three different textured soils; clay loam, sandy clay loam and sandy loam. Soils used in the experiment were collected from (i) agricultural field near new Science Faculty of Chittagong University (Clay loam soil), (ii) agricultural field near Shahid Minar of Chittagong University (Sandy clay loam soil) and (iii) Syedpara at Hathazari Upazilla under Chittagong district ( Sandy loam soil) from a depth of 0-15 cm. Soil samples were air dried and passed through a 2.00 mm sieve to separate dry roots, grasses and other particulate materials. A portion of the soils passed through 2.00 mm sieve was used for laboratory analyses. The properties of three different textured soils are presented Table 1. Particle size distribution was determined by hydrometer method of Day (1965) and . Earthen pots wre filled with soil @ 8 kg pot. Different levels of mercury ( 0. 00, 0.25, 0.50, 1.00, 1.50 and 2.00 mg Hg kg-1 soil) were applied in soil in solution form as HgCl_2. Each treatment was replicated thrice and the pots were arranged in randomized block design. The doses of nitrogen (as Urea), P (as Triple super phosphate), K (as Muriate of potash) and S (as Zinc sulfate) were applied in the pot experiment (110 kg N, 25 kg P, 60 kg K, 15 kg S ha-1 soil). According to BARC (1997) recommendation, 1/3 N, and whole of P, K, S were applied during soil preparation. The second 1/3 N was applied at rapid tillering stage and the rest 1/3 N was applied as broadcast before 5-7 days of panicle initiation. Four seedlings of 30 days’ old and of uniform size of a high yielding rice variety, BR 29, were transplanted in each pot. The level of standing water at a height of 2.5 ±0.5 cm above the soil surface was maintained by periodic addition of tap water. Growth parameters such as plant height, tiller number were recorded at 70 days after transplantation (DAT) and panicle number, dry weight (straw and root) and grain yield at maturity. At maturity, rice plants were harvested just above the soil surface level and separated into straw and rice grain. Roots were collected carefully and washed thoroughly with tap water first to remove adhering soil particles and then with distilled water. The straws were also washed to remove dust particles. Root, straw and grains were oven dried at 650 C for 72 hours and weights were recorded. The experimental data were statistically analyzed. The significance of differences between the means of the treatments was evaluated by one way analysis of variance followed by Duncan’s Multiple Range Test at the significance level of 5%.

Source of Information: Soil & Environ, 27(1):23-28,2008

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Growth and yield, in general, was better in the clay loam soil and poorer in the sandy loam soil. The application of mercury resulted significant decrease in plant height, tiller number , panicle number, grains /panicle. The number of unifilled grains/panicle showed the opposite trend of change to that of grains/panicle, the highest being observed with the highest rate of Hg application. Grain yield gradually decreased from control to the highest rate of Hg application indicating unfavorable effects of Hg on grain filling process.

Knowledge Management: Journal