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Methane Flux from Irrigated Paddy Agro-ecosystem and Rice Productivity Associated with the Phenological Characteristics of Rice Cultivars Under Silicon Fertilization

M. A. Ali
Department of Environmental Science, Bangladesh Agricultural University, Mymensingh

P. J. Kim
Department of Environ-biotechnology, Applied Life Science, Graduate School, Gyeongsang National University, Jinju, South Korea

C. S. Lim
Department of Environ-biotechnology, Applied Life Science, Graduate School, Gyeongsang National University, Jinju , South Korea

Abstract/ Executive Summary:

A field experiment was conducted to investigate the responses of Japonica and Indica type rice cultivars in relation to plant growth, physiology, yield and methane (CH₄) emission patterns under silicon fertilization. Silicon amendment significantly reduced CH₄ emission rate, while increased rice productivity in both cultivars. CH₄ flux was also regulated by the individual varietal characteristics. Indica type rice cultivar (IRATOM 24) showed higher CH₄ emission rate as compared to that of Japonica type cultivar (Dongjinbyeo) during the whole cropping period, mainly of higher vegetative growth and superior physiological traits such as active tillering and photosynthetic rate, shoot and root growth rate, and the easy conductivity of CH₄ gas via well developed aerenchyma tissue. The highest CH₄ peak was observed at flowering to heading stage, which decreased sharply in both cultivars at ripening stage, due to plant aging and a decrease in the photosynthetic rate of rice cultivars. Silicon amendment decreased the total seasonal CH₄flux by 20 % and 22 %, while increased rice grain yield by 20 % and 18 % in Indica and Japonica cultivars, respectively. There were positive correlations of CH₄ emission with the number of tillers, leaf area index and above ground biomass in both cultivars, while a strong negative correlation was observed between total seasonal CH₄ flux and the content of iron oxides in soil at harvesting stage. This implies the released iron materials from the applied silicate fertilizer acted as electron acceptors and ultimately suppressed CH₄ emissions.

Keywords: Methane emissions, Electron acceptors, Silicon, Rice cultivars, Aerenchyma, CO2 assimilation

Location: Agronomy field, Gyeongsang National University, Korea

Start Date: 00-01-2007

End Date: 00-12-2007

Program Area: Risk Management in Agriculture

Commodity: Rice

Objectives:

1. To investigate the responses of Japonica and Indica type rice cultivars in relation to plant growth, physiology, yield and methane (CH₄) emission patterns under silicon fertilization.

Methodology:

Estimation of methane flux - Methane emission from irrigated rice field was calculated from the increase in CH4 concentrations per unit surface area of the chamber for a specific time intervals. A closed-chamber equation was used to estimate methane fluxes from each treatment. F = ρ. V/A. Δc/Δt.273/T where, F= methane flux (mg CH⁴ m² hr^-1 ), ρ = gas density (0.714 mg cm^-3), V = volume of chamber(m³), A = surface area of chamber (m²), H = height of the chamber(m), Δc/Δt = rate of increase of methane gas concentration in the chamber (mg m^-3 hr^-1), T (absolute temperature) = 273 + mean temperature in chamber(⁰C ). Total methane flux for the entire cropping period were computed by the formula: Total CH4 flux = Σin (Ri x Di ), where Ri is the rate of methane flux (g m^-2 d^-1 ) in the ith sampling interval, Di is the number of days in the i th sampling interval, and n the number of sampling intervals. Investigation of soil properties - Soil redox potential (Eh) and flood water pH were measured every week interval by Eh meter (PRN-41, DKK-TOA Corporation) and pH meter (Orion 3 star, Thermo electron corporation), respectively, during rice cultivation. At the harvesting stage, soil bulk density was analyzed using cores (volume 100 cm³, inner diameter 5 cm), filled with fresh moisture soils. The collected soil core samples were dried in oven at 105º C for 24 hrs and then measured the weight of dried core samples. Soil porosity was calculated using the bulk density (BD) and particle density (PD, 2.65 Mg m^-3) according to the equation: Porosity (%) = (1-BD/PD) ×100. The collected surface (0–15-cm depth) soil samples were air-dried, sieved (<2mm) and analyzed for chemical properties: pH (1:5 with H2O), organic matter content, exchangeable Ca2+, Mg2+, and K+ (1 M NH4-acetate pH 7.0, AA, Shimazu 660), and available silicate content (1 M Na-acetate pH 4.0, UV spectrometer). The available phosphate content was determined using Lancaster method. Ferrous iron concentrations in fresh soil samples were determined by 2M Na-acetate extraction method. In the dried soil, the total soil iron, active iron and free iron concentrations were determined by modified acid digestion (12 M HCl), acid ammonium oxalate in darkness and citrate dithionite bicarbonate dissolution procedures, respectively. Statistical analysis - Statistical analysis were conducted using SAS software.

Source of Information: J. Environ. Sci. & Natural Resources, 2(1): 191-198, 2009; ISSN 1999-7361

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

CH₄ flux was regulated by the individual varietal characteristics. The Indica type rice cultivar (IRATOM 24) with higher vegetative growth and physiological traits such as active tillering and photosynthetic rate, root volume and porosity, and with well developed aerenchyma tissue emitted significantly higher amount of CH₄ as compared to that of Japonica cultivar. Silicate fertilization improved soil properties such as soil porosity, soil Eh and enriched the content of active iron and free iron oxides which acted as electron acceptors, thereby, suppressed CH₄ emission.

Knowledge Management: Journal