Effects of disturbance and glucose addition on nitrous oxide and carbon dioxide emissions from a paddy soil

The effects of disturbance and glucose addition on N2O and CO2 emissions from a paddy soil at 45% WFPS (water-filled pore space) and at 25 °C were determined. During a 45-day incubation, disturbances with and without glucose addition were imposed 0, 1, 3, and 5 times. The total amount of glucose added to soil with 1, 3, and 5 disturbances was equal (0.6% of oven-dry soil basis). Strong nitrification occurred in the paddy soil during the incubation. Disturbance alone did not influence N2O and CO2 emissions significantly, but disturbance with glucose addition did (P < 0.01). A flush of N2O as well as CO2 was always observed following disturbance with glucose addition. The discrepancy in N2O emission between disturbance alone and disturbance with glucose addition was ascribed to the different magnitude of denitrification and/or heterotrophic nitrification. Greater cumulative emission of N2O was observed in the treatment of three disturbance times with glucose addition (4.3 mg N kg−1 soil), compared with five disturbances with glucose addition (2.5 mg N kg−1 soil) and one disturbance with glucose addition (2.5 mg N kg−1 soil). Cumulative CO2 emission was significant larger in one and three disturbances with glucose addition than that five disturbance with glucose addition. Supplies of available organic C appear to be a critical factor controlling denitrification and/or heterotrophic nitrification processes and N2O emission under relatively low moisture conditions, i.e. 45% WFPS.