Abstract
Active movement of methane (CH_4) from flooded paddy soils to the atmosphere through rice plant was found with the range of 1.6-230 μg C/30 min/pot (0.16-23 mg C/h/m^2) by using acrylic chamber method in pot experiments conducted from August to October. The rate of CH_4 emission was influenced by growth of rice, light conditions, soil type, organic matter application to the soil, injection of solutions to rice rhizosphere, etc. Methane emissions through rice plant became maximum at heading stage and also at late afternoon. Applications of rice- and wheat-straw to the soils enhanced CH_4 emissions to 2-10 times. Rice plant in gley soil gave the higher rate of CH_4 emissions, followed by gray lowland soil and brown lowland soil in this order. Immediately after injection of CH_4-saturated water to rice rhizosphere, a large amount of CH_4 was discharged from shoot of rice plant, while CH_4 emission gave peak at 22 days after injection of sodium acetate solution to the rhizosphere. The rate of CH_4 emission from cross section of rice stem decreased one slightly and then increased to 1.5-4 times higher than the original level 4 h after cutting. Possible mechanism of the CH_4 movement in the rice plant was discussed.
