稻草还田下添加DCD对稻田CH4、N2O和CO2排放的影响

为研究秸秆还田下硝化抑制剂的效应,本研究借助温室盆栽,设置5个处理:不施肥(CK)、传统施肥(CF)、传统施肥配施硝化抑制剂双氰胺DCD(CF+DCD)、传统施肥稻草还田(CF+S)、传统施肥稻草还田配施DCD(CF+S+DCD),探讨秸秆还田下施用DCD对水稻整个生育期土壤CH_4、N_2O和CO_2排放的影响。结果表明:整个生育期,CH_4和CO_2排放量以CF+S最高,CF+S+DCD次之,而CK最低;N_2O排放量以CF最高,CF+DCD次之,而CF+S+DCD最低。与CF和CF+S相比,施用硝化抑制剂后CH_4和N_2O减排效果显著,而CO_2减排不显著。就水稻产量、综合温室效应(GWP)、温室气体强度(GHGI)和净生态系统经济预算(NEEB)而言,秸秆还田和硝化抑制剂施用,都可显著提高水稻产量和NEEB,而降低GWP和GHGI;与CF和CF+S相比,施用硝化抑制剂后,CF+DCD和CF+S+DCD分别增产9.5%和10.0%,NEEB增加16.8%和20.1%;GWP分别降低23.7%和21.0%,GHGI降低23.7%和21.1%。可见,无论稻草还田与否,硝化抑制剂对温室气体排放及水稻产量的影响效应比较稳定。因此,稻草还田配施DCD(即CF+S+DCD处理)在保证水稻产量的基础上,显著降低稻田土壤CH_4和N_2O排放,是一种经济可行的温室气体减排措施。

Effects of DCD addition on CH4, N2O and CO2 emissions from paddy field under rice straw incorporation

Incorporation of crop residues in agricultural soils can maintain soil organic matter, but simultaneously stimulates greenhouse gas emission. The application of the nitrification inhibitor has been demonstrated to inhibit effectively greenhouse gas emission. However, it remains largely unknown in effects of the nitrification inhibitor application on soil CH₄, N₂O and CO₂ emissions under straw return in farmland.In the present study, the emissions of farmland soil CH₄, N₂O and CO₂ under rice straw return were investigated and estimated when the nitrification inhibitor(dicyandiamide, abbreviated DCD) was applied during the whole rice growing season through the pot experiment. The experiment included five treatments:conventional fertilization(CF), conventional fertilization plus DCD(CF+DCD), conventional fertilization plus straw return(CF+S), conventional fertilization plus straw return and DCD(CF+S+DCD), and no input of fertilizers as control(CK). The results showed that CH₄ and CO₂ emissions during the whole rice growing season were highest in the CF+S treatment, followed by CF+S+DCD treatment, and lowest in CK treatment. In contrast, N₂O during the whole rice growing season were highest in the CF treatment, followed by CF+DCD treatment, and lowest in CF+S+DCD treatment. Compared with CF and CF+S treatments, the application of nitrification inhibitor significantly reduced CH₄ and N₂O emissions. In general, both straw return and nitrification inhibitor application significantly increased rice yield and net ecosystem economic budget(NEEB) but decreased global warming potential(GWP) and greenhouse gas intensity(GHGI). Compared with CF and CF+S treatments, the application of nitrification inhibitor increased crop yield by 9.5% and 10.0%, and NEEB by 16.8% and 20.1%, but decreased GWP by 23.7% and 21.0%, and GHGI by 23.7% and 21.1%. Thus, the application of nitrification inhibitor can significantly decrease greenhouse gas and sustain crop yield irrespective of straw return. Our results suggest that the combined of straw return and DCD application can be an effective greenhouse gas mitigation strategy without sacrifice crop yield.