Abstract：
Conservation tillage is widely used in farmland management for soil carbon sequestration, but it can also lead to potential emissions of nitrous oxide (N2O). Therefore, our study is aimed to investigate the effects of 15 years of no-tillage combined with four straw mulching levels of 0 % (NT0), 33 % (NT33), 67 % (NT67), and 100 % (NT100) compared to ridge tillage (RT) on the rates of N2O and N2 emissions and the respective contributions of four microbial pathways to N2O emissions. The incubation experiments were conducted at two different moisture levels (55 % and 100 % WFPS) by using dicyandiamide inhibition and 15N-labeling techniques. Soil samples were collected from the 0-20 cm and 20-40 cm soil depths across three maize growth stages: seedling, jointing, and maturity. Our results showed that conservation tillage significantly decreased the N2O + N2 emission at 55 % WFPS, but it has a reverse influence in N2O + N2 emission at 100 % WFPS. The proportion of N2O in gaseous N loss were higher at 100 % WFPS than at 55 % WFPS. Among the four microbial pathways for N2O emissions, autotrophic nitrification was the dominant pathway 55 %WFPS. The contribution of autotrophic nitrification remarkably decreased, co-denitrification and denitrification increased at 100 %WFPS. Overall, at 100 % WFPS, N2O emissions from all major microbial pathways were positively correlated with GWC, temperature, TC, TN, NH4+-N, and NO3--N, but negatively correlated with soil pH and C/N ratios. Our results suggest that long-term conservation tillage increases N2O and N2 emissions from the soil under water-saturated conditions by regulating soil nutrient levels, soil moisture, and microbial pathways. Therefore, we should consider the impact of conservation tillage on N2O emission risk when we attach importance to the role of conservation tillage in improving soil quality and increasing crop yields.
摘要：
保护性耕作在农田管理中广泛用于土壤固碳，但它也可能导致氧化亚氮（N2O）的潜在排放。因此,我们的研究旨在探讨15年免耕结合四种秸秆覆盖水平0%(NT0)的效果，33%（NT33），67%（NT67），在N2O和N2排放速率以及四种微生物途径对N2O排放的各自贡献方面，与脊耕（RT）相比，为100％（NT100）。在两种不同的湿度水平(55%和100%WFPS)下,通过使用双联脲抑制和15N标记技术进行孵育实验。从三个玉米生长阶段的0-20厘米和20-40厘米土壤深度收集土壤样品：幼苗，连接,和成熟。我们的结果表明，保护性耕作显着降低了55％WFPS下的N2ON2排放，但它在100%WFPS下对N2O+N2排放有相反的影响。在100％WFPS下，N2O在气态N损失中的比例高于55％WFPS。在N2O排放的四种微生物途径中，自养硝化是主要途径55%WFPS。自养硝化的贡献显著下降，共反硝化和反硝化在100%WFPS时增加。总的来说,在100%WFPS，所有主要微生物途径的N2O排放与GWC呈正相关，温度,TC,TN,NH4+-N,和NO3--N,但与土壤pH和C/N比呈负相关。我们的结果表明，长期保护性耕作通过调节土壤养分水平增加了水饱和条件下土壤中N2O和N2的排放，土壤湿度,和微生物途径。因此,在重视保护性耕作对改善土壤质量和提高作物产量的作用时,应考虑保护性耕作对N2O排放风险的影响。
