Effects of applying silicon on aerobic CH₄ oxidation in paddy field under nighttime warming and its response to nitrogen

【Objective】To study effects of silicon fertilizer on aerobic CH₄ oxidation rate in paddy field under warming condition，so as to provide scientific basis for exploring measures of greenhouse gas emission reduction under the background of global warming in the future.【Method】Open field warming system was used to warm the paddy soils at night.Four field treatments were set up： no silicon application at ambient nighttime temperature（CK），no silicon application at nighttime warming（NW），silicon application at ambient nighttime temperature（Si）and silicon application at nighttime warming（NW+Si）.The rhizosphere and non-rhizosphere surface soils were collected after four years of above-mentioned treatments.Soil under the conditions of no nitrogen and nitrogen addition（NH⁴⁺，NO^3-，urea） was used to study the aerobic CH₄ oxidation rate，and its carbon sequestration characteristics and its response to nitrogen（N）fertilization.【Result】Total organic carbon content and water-soluble organic carbon content in paddy field under Si treatment were 23.2 g/kg and 216.7 mg/kg，which were 10.5% and 26.7% higher than those in CK paddy field，respectively.However，organic carbon and water-soluble organic carbon in paddy field under NW treatment were 11.9% and 9.9% lower than that in CK paddy field.Aerobic CH₄ oxidation rates in rhizosphere soil under silicon application（Si and NW+Si treatments） were significantly higher than that under no silicon application（CK and NW treatments），and oxidation rate of paddy soils under Si treatment was 10.9 µg/（g·d），which was 45.3% higher than paddy field under NW treatment.Net increment of ¹³C soil organic carbon（ ¹³C-SOC）driven by CH₄ oxidation in non-rhizosphere soils under silicon treatment（Si and NW+Si）were 12.5-13.2 μmol/g，and carbon sequestration efficiency was 61%-66%，significantly higher than those in paddy field under no-silicon treatment（CK and NW）.This indicated that silicon application was in favor of more ¹³C-CH₄ carbon sequestration into SOC during aerobic CH₄ oxidation.The CH₄ oxidation rates of paddy fields substantially increased under N fertilization，especially in the non-rhizosphere soil under NW+Si treatment.In contrast，N fertilization had no significant effect on net increment of ¹³C-SOC，which resulted lower carbon sequestration efficiency driven by CH₄ oxidation in paddy soil.【Conclusion】Silicon application can alleviate inhibitory effect of nighttime warming on the CH₄ oxidation process in paddy fields and improve its carbon sequestration efficiency.