## 3 Results and Discussion
### Inter-Seasonal Variations in CH\({}_{4}\) Fluxes and Driving Factors  
As shown in Table 3, the total emissions of CH\({}_{4}\) were 21.63, 19.13, 23.95 and 14.52 g C-CH\({}_{4}\) m\({}^{-2}\) for late rice in 2018-2020 and early rice in 2020, respectively. The CH\({}_{4}\) emissions of the total growing season in this study were comparable to those in the studies by [PERSON] et al. [49] (19.20 g C-CH\({}_{4}\) m\({}^{-2}\) in a single-season paddy field in Yancheng, Jiangsu Province) and [PERSON] et al. [39] (20.78 g C-CH\({}_{4}\) m\({}^{-2}\) in a single-season paddy field in Nanjing, Jiangsu Province) but were lower than those found by [PERSON] et al. [50] (54.69 g C-CH\({}_{4}\) m\({}^{-2}\) in a rice-wheat rotation agroecosystem in Nanjing, Jiangsu Province) and greater than those found by [PERSON] et al. [66] (3.26 g C-CH\({}_{4}\) m\({}^{-2}\) in a single-season paddy field in the Philippines). Obviously, the seasonal total CH\({}_{4}\) emissions were site dependent and varied with time. The differences in these results are due to the different environmental conditions and field management practices. [PERSON] et al. [44] reported that CH\({}_{4}\) emissions for the whole growing season ranged from 2.5-11.1 g C m\({}^{-2}\) during 2009-2015 in a California paddy field, which was well below the emissions from Nanchang in this study. The mean T\({}_{\rm a}\) ofthe whole growing season averaged from 18.6 to 20.5 \({}^{\circ}\)C in California, and the greater temperature is thought to be the main reason for the greater CH\({}_{4}\) emissions in Nanchang. [PERSON] et al. [46] observed that CH\({}_{4}\) emissions ranged from 27.9 to 37.2 g C m\({}^{-2}\) in an Italian paddy field; in this case, water management can account for the differences between the two sites because the paddy field in Italy was continuously flooded before ripening without mid-season drainage. As shown in Table 3, the CH\({}_{4}\) emissions before mid-season drainage were 13.70, 16.24, 21.14, and 6.78 g CH\({}_{4}\) m\({}^{-2}\) for 2018-2020 late rice and 2020 early rice and accounted for 63.4%, 84.9%, 88.3%, and 46.7% of the whole growing season emissions, respectively. Before mid-season drainage, the CH\({}_{4}\) emissions of late rice in 2018 were lower than those in 2019 and 2020, which was attributed to the differences in planting type, irrigation type and climate. Late rice in 2018 was transplanted, but it was direct-seeded in 2019 and 2020; therefore, the periods before mid-season drainage were shorter in 2018. Additionally, because AWD was applied in 2018 late rice, the rice plants were dried several days after transplanting. Also, transplanted rice has a lower planting density than direct-seeded rice. Therefore, the GPP of late rice in 2018 was lower than that of late rice in 2019 and 2020 (as shown in Table 3, the GPP was 889.53, 1245.95 and 1081.13 g CO\({}_{2}\) m\({}^{-2}\) in 2018, 2019 and 2020 late rice, respectively). However, the CH\({}_{4}\) emissions of late rice in 2018 were higher than those in 2019 and 2020 after mid-season drainage, which was due to rainfall during mid-season drainage for late rice in 2018. [PERSON] et al. [31] reported that mid-season drainage decreased CH\({}_{4}\) emissions from an irrigated rice paddy, but if rainfall occurred during the period, the reduction effect on CH\({}_{4}\) emissions became small. As shown in Figure 5, the CH\({}_{4}\) flux did not drop sharply after mid-season drainage for late rice in 2018, which was consistent with [PERSON] et al. [31]. As shown in Figure 5, the difference in CH\({}_{4}\) emissions