[A-GE28] Subsurface Mass Transport and Environmental Assessment

[AGE28-05] Effect of Artificial Macropore to Methane Gas Emission from Rice Paddy Field.

Kota Hamaoka¹, *Yasushi Mori¹ (1.Graduate School of Environmental and Life Science, Okayama University)

Keywords:methane, macropore, GHG emission, paddy field

An experiment was conducted to clarify the effect of artificial macropores on the reduction of methane gas emissions, a greenhouse gas, from paddy fields. Acrylic columns with a diameter of 10 cm and a height of 30 cm were filled with paddy soil with or without drainage and with or without macropores, and gas emission experiments were conducted for 60 days under four control conditions. The additional soil was applied on top of the macropores so that methane-oxidizing bacteria could work in particular.
As a result, the redox potential of the drainage and macropore-applied samples was often positive, and methane gas emissions were suppressed. In particular, there was a positive linear proportional relationship between TOC and methane emissions in the effluent, and columns with higher methane emissions also had higher TOC and Fe concentrations in the effluent, indicating organic matter and Fe leaks. Under methane emission conditions, the columns were at risk of becoming aged paddy fields. Based on a series of experiments, it was recommended that early spring plowing should be light to leave pore structure of the previous crop and that plowing should be done in a normal manner to reduce methane emission.