Simulating methane emission from a Chinese rice field as influenced by fertilizer and water level

Abstract

Abstract:Natural and agricultural wetlands are considered to be the major sources of global atmospheric methane (CH 4 ). A onedimensional model was developed to simulate methane emission and used to examine the influence of various physical processes on the rate of methane emission. Three processes involved in the methane emission are implemented in the model: production, reoxidation and transport. Three transport pathways were considered: diffusion across water-air or soil-air interfaces, ebullition and diffusion through plants. These pathways are influenced by soil properties, plant growth, water-table conditions, temperature and external inputs (e.g. fertilizer). The model was used to examine the seasonal variation of the methane emission at a rice field in Hunan, China, which was observed during a field experiment for consecutive (early and late) rice seasons in 1992. The observed seasonal variations of methane emission, and role of plants in transporting methane to the atmosphere, are captured by the model simulation. Further model applications were conducted to simulate effects of fertilizer and water-level condition on the methane emission. The results indicate that unfermented organic fertilizer produces a higher methane emission rate than mineral fertilizer. The simulations with treatments of a deep-water covering and constant moisture reduced the methane emission. The rice field study provides a framework for further development of the model towards simulations based on spatially distributed variables (e.g. water table, soil temperature and vegetation) at a regional scale.

Influences of Hydrogen Bonding and Peripheral Chain Length on Mesophase Structures of Mesogen-Jacketed Liquid Crystalline Polymers with Amide Side-Chain Linkages

“…Among these interactions, hydrogen bonding has been extensively explored to tailor self-assembled nanostructures for the applications in the fields of biology and materials science. [15][16][17][18] Introducing amide groups, which can form hydrogen bonding, into MJLCPs might bring about a new way to control phase structures. Previously, we have synthesized 2-vinyl-1,4-phenylenediamine-based poly-2,5-bis(4-alkoxybenzamido)styrene, which exhibited a lyotropic nematic phase when methoxy groups were appended to the two ends of the mesogens.…”

Effect of Water-Saving Irrigation on CH₄ Emissions from Rice Fields

“…4), which in turn indicates that temperature is the key factor impacting emissions during these stages. Previous studies show that the diurnal variation pattern and magnitude of CH 4 emission are not related to the efficiency of soil CH 4 production, but depend on the transfer efficient of different emission passways that is affected by temperature (Yu et al, 2003). Under controlled irrigation conditions, emission rates were relatively high, which is an explanation of effects of temperature on plant transfer efficient.…”

Effects of Nitrogen Input and Aeration on Greenhouse Gas Emissions and Pollutants in Agricultural Drainage Ditches

“…CH 4 is produced by methanogenic archaea in anaerobic environments as they decompose organic matter, and soil organic carbon is an important substrate for the production of CH 4 [61,62]; therefore, the emission of CH 4 is highly positively correlated with the content of soil organic carbon, and soil ammonium nitrogen can promote the growth and reproduction of methanogenic archaea [63], indicating a high positive correlation between CH 4 emissions and soil ammonium nitrogen content. After its production, more than 80% of CH 4 is oxidized by aerobic methanotrophic bacteria before it is emitted into the atmosphere during its transport from the soil to the atmosphere [64]. It is evident that the higher the ORP of the water body, the more CH 4 is oxidized, hence there is a significant negative correlation between CH 4 emissions and the water body's ORP (p < 0.05).…”