In rice paddy fields, the soil water management used in
conjunction with most of the collected data was application
of mid-season drainage. N fertilizer inputs of 1–2 times
commonly occurred during the period of rice seedling and
tillering, when the rice paddy was continuously flooded
and anaerobic conditions prevailed. Due to the high CH4
concentration in the anaerobic soils, the application of N
stimulated the activity of methanotrophs to consume more
CH4, which subsequently decreased the CH4 emission relative
to control fields (Cai et al. 2007). The third and fourth N
fertilizer applications generally occurred during the panicle
initiation and graining stages. This significantly stimulated
rice growth, which subsequently increased the substrate to
produce more CH4 and increase plant body transport while
inhibiting CH4 oxidation (Cai et al. 2007). As a result, CH4
emissions significantly increased with 3–4 compared to 1–2
application times of N fertilizer