Search

Winter-flooded paddy is a typical rice-based cropping system to conserve water for the next rice growing season. Conversion of winter-flooded paddy to rice-wheat rotation has been widely adopted with the development of the water conservation infrastructure and the government's encouragement of winter agriculture in China in recent decades. However, the effects of this conversion on N 2 O emission are still not clear. Three winter-flooded paddy fields were studied in a split-plot design. One-half of each field was converted to rice-wheat rotation (RW), and the other half remained winter-flooded as rice-fallow (RF). Each plot of RW and RF was further divided into four subplots: three subplots for conventional N fertilizer application (RW-N C and RF-N C ) and one for unfertilized treatment (RW-N 0 and RF-N 0 ). Conversion of RF-N C to RW-N C increased the N 2 O emission up to 6.6-fold in the first year and 4.4-fold in the second year. Moreover, N 2 O emissions for the entire wheat season were 1.74–3.74 kg N ha −1 and 0.24–0.31 kg N ha −1 from RW-N C and RW-N 0 , respectively, and accounted for 78%–94% and 78%–97% of the total annual amount. N 2 O emitted during the first 11–21 days of the wheat season from RW-N C was 1.48–3.28 kg N ha −1 and that from RW-N 0 was 0.14–0.17 kg N ha −1 , which contributed to 66%–82% and 45%–71% of the total annual amount, respectively. High N 2 O fluxes occurred when the soil water-filled pore space (WFPS) was in the range of 68%–72% and the ratio of available carbon to nitrogen in the soil was <1.42. The contribution of WFPS and dissolved organic carbon (DOC) explained most of the variation of the N 2 O fluxes compared with the other measured environmental and soil factors. These findings suggest that the conversion of winter-flooded paddy to rice-wheat rotation increased N 2 O emissions that could be mitigated by controlling the soil moisture and ratio of available soil carbon to nitrogen. [ABSTRACT FROM AUTHOR]