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We investigate whether slag and biochar applications have subsequent effects on greenhouse gas emissions from paddy fields by applying biochar (B), slag (S), and a biochar-slag mix (BS) to paddy fields in the Fuzhou Plain, China. Applications of the three treatments along with a control (CK) of no amendment were made in 2015 before early and late rice seedlings were transplanted. Two years later in 2017, the CO 2 , CH 4 , and N 2 O emissions in the different treatments and control were measured in the early and late rice growing seasons. The results showed that, in the rice growing season, the averaged CO 2 emission in the control, biochar, slag, and mixed applications were (1723.66±194.56), (1245.52±155.05), (1140.29±79.68), and (1055.83±62.13) mg·(m 2 ·h) -1 , respectively. The CO 2 emissions from the three treatments were significantly lower than the control group ( P <0.05), and the reduction ratios of each treatment to the control were 27.74%, 33.84%, and 38.75%, respectively. The averaged CH 4 emissions in the control, biochar, slag, and mixed applications were (0.45±0.03), (0.40±0.05), (0.36±0.10), and (0.25±0.04) mg·(m 2 ·h) -1 , respectively, which were lower, but not significantly so ( P >0.05), than the control. The ratios of CH 4 emissions from each treatment to the control were 11.11%, 20.00%, and 44.44%, respectively. The averaged N 2 O emissions from the control, biochar, slag, and mixed applications were (62.47±27.00), (115.09±30.94), (79.75±24.98), and (112.68±23.59) μg·(m 2 ·h) -1 , respectively. In comparison to the control, the biochar, slag, and mixed treatments increased the N 2 O emissions by 84.23%, 27.66%, and 80.37%, respectively. The global comprehensive warming potential indicated that the application treatments increased the comprehensive warming potential of the early and late rice paddy ecosystems; after 2 years of applying slag and biochar treatments, their effect on the emission reductions were not obvious.