氮肥管理对夏玉米土壤CH4和N2O排放的影响

通过设置四个不同的氮肥管理措施, 即氮肥施用量300 kg N/ha (N300)和250 kg N/ha (N250)、改进的施肥模式(Optimized)以及施用缓释肥(SRU), 研究华北平原夏玉米生长季土壤与大气之间CH₄和N₂O的交换通量及相应措施的减排潜力. 结果表明, 在2008年整个夏玉米生长季, 土壤都是大气CH₄的净吸收库和N₂O的排放源. 夏玉米生长季土壤氧化吸收的CH₄总量从大到小依次为Optimized > N250 > SRU > N300, 对应的吸收总量依次为624.16、590.07、487.89以及316.02 g CH₄-C/ha, 各处理间氧化吸收的CH₄总量无显著差异. 与N300和N250这两个处理相比, 依据夏玉米对氮肥的需肥规律以及玉米根层土壤速效氮的供给能力而确定氮肥施用量, 同时再平衡施用磷肥和钾肥的改进施肥模式能够显著降低夏玉米生长季N₂O的排放. 施用聚乙烯包膜的尿素也能够显著降低夏玉米季N₂O的排放. 夏玉米生长季土壤排放的N₂O总量从大到小依次为N300 > N250 > Optimized > SRU, 对应的排放总量依次为3462.18、2340.07、1680.00以及911.91 g N2O-N/ha, 相应的N₂O排放系数分别为1.15%、0.94%、0.91%以及0.30%.

Effects of nitrogen management on methane and nitrous oxide emissions from summer maize soil in North China Plain

CH₄ and N₂O fluxes from summer maize soil in North China Plain were measured in 2008 using a close chamber method. Four different nitrogen management levels were used: nitrogen application at the rate of 300 kg N/ha (N300), nitrogen application at the rate of 250 kg N/ha (N250), improved nitrogen management methods (Optimized), and the application of slow-release urea (SRU). The summer maize soil was a net sink of CH₄ and an emission source of N₂O during the whole growing season. The accumulative CH₄ oxidation rate of Optimized, N250, SRU, and N300 was 624.16, 590.07, 487.89, and 316.02 g CH₄-C/ha, respectively. The difference of accumulative CH₄ oxidation rate between four treatments was not significant (t-test, P < 0.05). The Optimized treatment, which applied nitrogen according to maize demand and mineral nitrogen (N_min) content in the soil of maize root layer, and balance phosphorus and potassium fertilizer application rate, could reduce N₂O emission obviously compared to N300 and N250. The application of SRU could also reduce N₂O emission significantly. The accumulative N₂O emissions of N300, N250, Optimized and SRU were 3462.18, 2340.07, 1680.00, and 911.91 g N₂O-N/ha, respectively, and the fertilizer-induced N₂O emission factors were 1.15, 0.94, 0.91, and 0.30%, respectively.