Emission Characters and Environmental Cost of CH_4 and N_2O from Agricultural Activities of Double Rice Cropping in Central and South China
Paddy field is an important source of atmospheric CH4 and N2O. Based on the agricultural date from National Bureau of Statistics of China, from 1992 to 2011, the CH4 and N2O emission and its greenhouse effect environmental cost of double rice cropping in Central and South China were estimated and analyzed, and reduction methods of CH4 and N2O emission were recommended for rice cultivation. The results showed that(1) In Central and South China, the annual emission variation of CH4 and N2O had a similar "V" trend, and a turning point was happened in 2003.(2) The average annual emission of CH4 and N2O was gradually decreased every 5 years from1992 to 2011, but the unit area emission of rice cultivation of CH4 and N2O were increased gradually. And the variation trend of environment cost of greenhouse effects of CH4 and N2O were the same as their emission trend.(3) In Central China, the average annual emission of CH4 and N2O was 200.13×104, 0.66×104t respectively, and the unit area emission was 234.89, 0.89 kg/ha correspondingly. In South China, the average annual emission of CH4 and N2O was 125.42×104, 0.48×104t, and the unit area emission was 216.78, 1.17 kg/ha respectively.(4) In Central China, the environment cost of greenhouse effects of CH4 and N2O was 7.05×109, 0.41×109USD and the unit area cost was 98.65, 5.54 USD/ha, and in the South China, the environment cost of greenhouse effect of CH4 and N2O was 4.60×109, 0.40×109USD and the unit area cost was 91.05, 7.25 USD/ha.(5) The highest of CH4 and N2O emission was in Hunan and Jiangxi in Central China, and that in South China they was in Guangdong andGuangxi. To reduce the emission of CH4 and N2O in these areas is of a top priority. According to the study, in Central and South China, the emission and environmental cost of CH4 and N2O was so high that it should be reduced in a manner of innovative rice planting technology.