施氮量对海南燥红壤和砖红壤N2O/CO2排放的影响

利用室内培养实验，分析燥红壤和砖红壤中分别施加N0（不添加氮素）、N1（氮添加量为100mg·kg^?1）、N2（氮添加量为200mg·kg^?1）和N3（氮添加量为300mg.kg^?1）4个水平氮后对土壤性质及N₂O、CO₂排放的影响。结果表明：氮肥添加显著降低了土壤pH和有机碳含量。相较于N0，燥红壤N1、N2和N3处理pH和有机碳降幅分别为8%～18%和4%～12%，砖红壤降幅分别为5%～23%和3%～15%；添加氮肥后各处理土壤全氮含量显著增加，燥红壤和砖红壤分别增加15%～54%和13%～52%。氮施入增加了土壤NH₄⁺?N和NO₃^??N含量，各处理土壤铵态氮和硝态氮含量均表现为N3>N2>N1>N0。氮添加促进土壤N₂O和CO₂排放，相较于N0，燥红壤N₂O和CO₂累积排放量分别增加1176%～2425%和124%～281%，砖红壤分别增加1054%～1887%和138%～256%。施氮量和土壤类型是影响农田土壤N₂O和CO₂排放的重要因素。土壤N₂O和CO₂排放与施氮量呈线性显著相关，减少施肥是降低土壤N₂O排放最直接和最有效的措施。与砖红壤相比，燥红壤N₂O和CO₂排放对氮素添加的响应更敏感。

Effects of Nitrogen Application Rate on N2O and CO2 Emission of Dry Red Soil and Latosol in Hainan

The effects of four levels of nitrogen, N0 (without nitrogen), N1 (100mg.kg^?1), N2 (200mg·kg^?1) and N3 (300mg·kg^?1) on soil properties, N₂O and CO₂ emissions in dry red soil and latosol were analyzed by laboratory incubation experiments. The results showed that nitrogen fertilizer significantly declined soil pH and organic carbon content. Compared with N0, N1, N2 and N3 treatments decreased pH and organic carbon by 8%?18% and 4%?12% in dry red soil, respectively, and latosol decreased by 5%?23% and 3%?15%, respectively. The total nitrogen content in dry red soil and latosol increased by 15%?54% and 13%?52%, respectively. Nitrogen application increased the contents of NH₄⁺?N and NO₃^??N, and the contents of NH₄⁺?N and NO₃^??N were N3>N2>N1>N0. Nitrogen addition promoted soil N₂O and CO₂ emissions. Compared with N0, cumulative N₂O and CO₂ emissions in dry red soil increased by 1176%?2425% and 124%?281%, respectively, and those in latosol increased by 1054%?1887% and 138%?256%, respectively. Nitrogen application rate and soil type are important factors affecting soil N₂O and CO₂ emissions. There was a significant linear correlation between soil N₂O and CO₂ emissions and nitrogen application rate. Reducing fertilization is the most direct and effective measure to reduce soil N₂O emissions. Compared with latosol, N₂O and CO₂ emissions were more sensitive to nitrogen addition in dry red soil.