Soil CO2 fluxes from direct seeding rice fields under two tillage practices in central China

Agricultural practices affect the production and emission of carbon dioxide (CO2) from paddy soils. It is crucial to understand the effects of tillage and N fertilization on soil CO2 flux and its influencing factors for a better comprehension of carbon dynamics in subtropical paddy ecosystems. A 2-yr field study was conducted to assess the effects of tillage (conventional tillage [CT] and no-tillage [NT]) and N fertilization (0 and 210 kg N ha−1) on soil CO2 fluxes during the 2008 and 2009 rice growing seasons in central China. Treatments were established following a split-plot design of a randomized complete block with tillage practices as the main plot and N fertilizer level as the split-plot treatment. The soil CO2 fluxes were measured 24 times in 2008 and 17 times in 2009. N fertilization did not affect soil CO2 emissions while tillage affected soil CO2 emissions, where NT had similar soil CO2 emissions to CT in 2008, but in 2009, NT significantly increased soil CO2 emissions. Cumulative CO2 emissions were 2079–2245 kg CO2–C ha−1 from NT treatments, and 2084–2141 kg CO2–C ha−1 from CT treatments in 2008, and were 1257–1401 kg CO2–C ha−1 from NT treatments, and 1003–1034 kg CO2–C ha−1 from CT treatments in 2009, respectively. Cumulative CO2 emissions were significantly related to aboveground biomass and soil organic C. Before drainage of paddy fields, soil CO2 fluxes were significantly related to soil temperature with correlation coefficients (R) of 0.67–0.87 in 2008 and 0.69–0.85 in 2009; moreover, the Q10 values ranged from 1.28 to 1.55 and from 2.10 to 5.21 in 2009, respectively. Our results suggested that NT rice production system appeared to be ineffective in decreasing carbon emission, which suggested that CO2 emissions from integrated rice-based system should be taken into account to assess effects of tillage.