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In order to reveal the rule of N2O emission from paddy fields under water and biochar management and the effects of nitrogen use and loss in different stages on N2O emission, two water management modes (dry-wet-shallow, conventional flooding irrigation) and four straw biochar application levels (0t/hm2, 2.5t/hm2, 12.5t/hm2 and 25t/hm2) were set up. The N2O emission from paddy fields, as well as the absorption and utilization efficiency and loss rate of basal fertilizer, tiller fertilizer and panicle fertilizer, were studied by combining field plot and 15N tracer micro plot. The relationship between N2O emission and the use and loss of nitrogen fertilizer in each stage was analyzed. The results showed that the N2O emission patterns of the two irrigation modes were different. The cumulative N2O emissions of the dry-wet-shallow irrigation mode were significantly higher than that of the conventional flooding irrigation mode (P<0.05). The cumulative N2O emissions of the two irrigation modes were larger at tillering stage and jointing booting stage. The cumulative N2O emission of dry-wet-shallow irrigation mode was higher than that of conventional flooding irrigation. The application of biochar reduced the cumulative N2O emission in each growth stage. The absorption and utilization efficiency of basic fertilizer was lower in dry-wet-shallow irrigation mode than that in conventional flooding irrigation mode, but the absorption and utilization efficiency of tiller and panicle fertilizer was significantly higher than that of conventional flooding irrigation (P<0.05). The application of appropriate amount of biochar could increase the absorption and utilization efficiency of nitrogen fertilizer applied in each stage. The correlation analysis showed that the total N2O emission was significantly and negatively correlated with the absorption and utilization efficiency of tiller and panicle fertilizer (P<0.05), and significantly and negatively correlated with the absorption and utilization rate of base fertilizer (P<0.01), and significantly and negatively correlated with the absorption and utilization efficiency of base fertilizer, tiller fertilizer and ear fertilizer under the conventional flooding irrigation mode (P<0.01);the total N2O emission under the two irrigation modes was significantly and negatively correlated with the loss of base fertilizer and tiller fertilizer. The loss rates were significantly and positively correlated (P<0.05).