Abstract:
To investigate the interactive effects of different amount of biochar application and earthworm inoculation on soil N
2O and CO
2 emissions, a 50-day incubation experiment was conducted in the present study. Six treatments were arranged for the experiment: soil without earthworm and biochar (S), soil with earthworm inoculation (SE), soil with low amount of biochar addition (SL), soil with low amount of biochar addition and earthworm inoculation (SLE), soil with high amount of biochar addition (SH) and soil with high amount of biochar addition and earthworm inoculation (SHE). Results show that biochar addition led to a significant decrease of earthworm's biomass. Compared with the initial stage of incubation, earthworm's biomass decreased by 18% in SE, 26% in SLE, and 37% in SHE treatment. At the end of incubation, cumulative soil N
2O emissions for SE, SLE and SHE treatments were 589.8, 538.0 and 258.3 μg·kg
-1, respectively, which were significantly higher than the counterpart value of non-earthworm treatments (the cumulative N
2O emission was 57.1, 34.5 and 23.4 μg·kg
-1 for S, SL and SH treatments, respectively). Biochar addition depressed the earthworm induced N
2O emission. In general, more the biochar was added, more the obvious effect was detected. At the end of incubation, the cumulative soil CO
2 emissions were 686.1, 682.2 and 420.7 mg·kg
-1 for SE, SLE and SHE treatments, respectively, which were significantly higher than the counterpart value of non-earthworm treatments (the cumulative CO
2 emission were 346.9, 268.7 and 165.9 mg·kg
-1 for S, SL and SH treatments, respectively). Biochar addition depressed the earthworm induced CO
2 emission, but the significant difference only was observed between the high amount of biochar application and the non-biochar application treatment. Analysis of between-subjects effects show that earthworm, biochar and the interaction effect between them had significant effects on N
2O and CO
2 cumulative emission. Biochar application increased soil pH, but decreased soil inorganic N content. Overall, high amount of biochar application led to a higher soil pH, a lower soil inorganic N content and a negative effect on earthworms' activities, which contributed to the decreased N
2O and CO
2 emissions with earthworm presence.