A three-year experiment of annual methane and nitrous oxide emissions from the subtropical permanently flooded rice paddy fields of China: Emission factor, temperature sensitivity and fertilizer nitrogen effect

•3-year measurements of GHG emission in subtropical permanently flooded rice system.•Nitrogen fertilizer application decreased CH4 emissions.•Nitrogen fertilizer application did not affect N2O emissions.•The Q10 values of N2O emissions were greater than those of CH4 emissions.•EFd for the permanently flooded rice was much lower than the IPCC default value.