优化施肥下华北冬小麦/夏玉米轮作体系农田反硝化损失与N2O排放特征

在田间条件下，应用乙炔抑制-原状土柱培养法测定优化施肥下华北冬小麦/夏玉米轮作体系土壤反硝化和N2O的排放特征。研究表明:冬小麦和夏玉米整个生育期反硝化速率和N2O排放通量均表现出明显的季节性变化，且均与土壤水分和无机氮浓度呈显著正相关。小麦季和玉米季的反硝化损失量及N2O排放量均表现出随施肥量的降低而降低，夏玉米季的反硝化损失量和N2O排放量均高于小麦季。小麦季的反硝化损失量和N2O排放量习惯施肥处理是氮肥减量后移处理的1.62和1.67倍，玉米季分别为2.01和2.00倍。氮肥减量后移可能是通过改变土壤无机氮浓度而降低反硝化损失量和N2O排放量。

Effect of optimized nitrogen application on denitrification losses and N2O emissions from soil in winter wheat/summer corn rotation system in North China

A field experiment was conducted characterize denitrification and N₂O emission from soil under optimized nitrogen fertilization in winter wheat-summer corn rotation system in North China using acetylene inhibition-intact soil core incubation technique. Results showed that there were significant seasonal variations of denitrification rate and N₂O emission flux during winter wheat-summer corn growth periods, and positive correlations existed between inorganic nitrogen concentration (NH₄⁺-N, NO₃^--N) and denitrification rate. Total denitrification losses and N₂O emission amounts from soil in winter wheat-summer corn rotation system were observed to be reduced with decreasing of N application rate, and which in winter wheat season were found to be less than those in summer corn season. Total denitrification losses and N₂O emission amounts under conventional N fertilization were respectively 1.62 and 1.67 times as high as those under optimized N fertilization during winter wheat growth periods, and 2.01 and 2.00 times during summer corn growth periods, which N application rate decreased by 30% and postponing N application as compared with conventional N fertilization with an application rate of N300 kg/hm². Therefore, postponing N application could reduce denitrification losses and N₂O emission through modifying soil inorganic nitrogen concentration.