Methane Emission Situation of Rice Paddy in Red River Delta

Paddy rice cultivation is a cause of methane emission, which belongs to green house gases.  This study was carried out to investigate methane emission situation of rice paddy (at fully initiation stage) at some provinces of the Red river delta (Hai Phong, Thai Binh, Nam Dinh, Hai Duong, and Hanoi). 10 samples were taken in each province at the summer rice season 2010. Results showed that the average methane flux of 5 provinces was the lowest in Thai Binh (39.5 mg mgCH₄/m²/h) and was the highest in Nam Dinh (61.3 mgCH₄/m²/h). The methane flux in Hai Phong varied from 31.4 to 69.9 mgCH₄/m²/h, Thai Binh varied from 32.1 to 60.3 mg mgCH₄/m²/h, Nam Dinh varied from 40.7 to 94.2 mgCH₄/m²/h, Hai Duong varied from 30.9 to 84.3 mg mgCH₄/m²/h Hanoi varied from 33.1 to 57.9 mg mgCH₄/m²/h. In the summer rice season 2010, methane flux reached the highest value at 5 weeks after transplanting, which was 72.3 and 66.0 mg mgCH₄/m²/h in experiment sites of Hai Duong and Hanoi, respectively. Then it gradually reduced to the end of growing season. In the spring rice season 2011, methane flux gained its peak at 9 weeks after transplanting, which was 53.6 and 44.7 mg mgCH₄/m²/h at 2 sites, respectively, and it was lower than methane flux of the summer season 2010. The research results of correlation between methane flux with soil properties showed that methane flux was tightly correlated inversely with pH_KCl in Hai Phong soils (r = -0.82), with available Mn and Eh in Thai Binh, Hai Duong, and Nam Dinh soils (r from -0.55 to -0.85), and correlated positively with organic matter content in Hanoi soils (r=0.6).