Methane emission from biogenic sources is very important for the global CH₄ budget. Paddy fields have been identified as one of the major sources of anthropogenic CH₄ emissions to the atmosphere. Rice is the major cereal crop to feed more than half of the world's population, and the production of rice will increase with the expanding world population and may increase the associated CH₄ emissions and thereby accelerate global warming effects. Therefore, feasible soil management strategies need to be developed for reducing CH₄ emission from intensive rice farming while sustaining rice productivity.
Among the various factors, the content of soil oxidants (electron acceptors) and reductants (electron donors) play vital role in controlling CH₄ emissions from wetland rice agriculture. While electron acceptors can control CH₄ emission from paddy fields, it can be regenerated during the drained period. For example, Iron reduction is a dominant redox process within the redox sequence of anaerobic systems, and may suppress CH₄ production and its emission.
A field experiment was carried out in the Wufeng Agronomy Field of the Fujian Academy of Agricultural Sciences (26.1°N, 119.3°E), Southeast China during the rice growing season in April to July 2011. The soil at the experimental site was moist, poorly drained, clay loam, paddy field soil type. Bulk density of the soil before experimentation was 1.1 g cm^-3, and other chemical properties were: pH 6.5, organic carbon 18.1 g/kg, total N 1.2 g/kg, total P 1.1 g/kg.
In order to clarify the effect of iron slag amendment on paddy field methane production, oxidation and emission, the methane production, oxidation and emission of control (CK) and after 2 Mg/hm²(Fe Ⅰ), 4 Mg/hm²(Fe Ⅱ), and 8 Mg/hm²(Fe Ⅲ) iron slag application were determined by static chamber-gas chromatogram. The results showed: Methane production rates of CK, Fe Ⅰ, Fe Ⅱ and Fe Ⅲ plot were 0.06-8.87, 0.12-8.28, 0.15-7.84, 0.17-7.82 mg·m^-2· h^-1 during observation date and averaged values were 4.68, 3.92, 3.14, 2.76 mg·m^-2·h^-1,respectively. Methane oxidation rates were 0.02-1.27, 0.09-0.95, 0.09-1.54, 0.09-2.79 mg·m^-2·h^-1 and averaged values were 0.46, 0.47, 0.59, 0.55 mg·m^-2·h^-1, respectively. Methane emission fluxes were 0.04-7.99, 0.03-7.33, 0.06-6.30, 0.08-5.12 mg·m^-2·h^-1 and averaged values were 3.11, 2.29, 1.76, 1.59 mg·m^-2·h^-1, respectively. Iron slag suppressed methane production and emission, while it increased CH₄ oxidation rate.