不同肥源条件下Zn对农田土壤N2O排放的影响及其机制

为探究锌（Zn）污染对农田土壤氧化亚氮（N₂O）排放的影响，分别以猪粪和尿素为肥源进行室内培养实验，对比分析不同含量Zn （0、50、500、1500和5000mg/kg）对N₂O排放的影响及其机制，并在培养第52d向所有处理再次添加尿素以探究其长期效应，共培养80d.结果表明：第1次添加肥料阶段，在尿素为肥源处理中不同含量Zn均表现为显著抑制作用（P<0.05），而猪粪为肥源处理中除50mg/kg无显著影响外（P>0.05），其它含量处理均显著促进N₂O排放（P<0.05）.第2次添加肥料阶段，不同肥源条件下Zn的作用规律一致，即50mg/kg无显著影响（P>0.05），500和1500mg/kg显著提高N₂O排放而5000mg/kg处理与之相反（P<0.05）.此阶段500、1500和5000mg/kg处理以猪粪和尿素为肥源时其N₂O累积排放量与同肥源对照的比值分别为3.49、3.13、0.01和2.53、2.74、0.04，可见同等含量Zn在猪粪为肥源条件下作用更强，500和1500mg/kg Zn的促进机制为Zn提高了土壤中NH₄⁺-N、NO₃^--N含量以及控制反硝化过程N₂O产生和还原功能基因相对丰度的比值（nirS/nosZ），而5000mg/kg Zn抑制了土壤中NH₄⁺-N进一步转化为NO₃^--N，从而降低了N₂O排放.

Effects and mechanisms of Zinc on nitrous oxide emissions from farmland soil under different fertilization conditions

To understand effects and mechanisms of different Zinc (Zn) application rates (0, 50, 500, 1500 and 5000mg/kg) on nitrous oxide (N₂O) emissions from farmland soils under different nitrogen fertilizers (manure and urea), an 80-day simulating incubation experiment was conducted, and urea was added again to all treatments on the day 52 of incubation to explore its long-term effects. The results showed that Zn addition significantly reduced N₂O emissions in urea-fertilized soil while enhanced N₂O emissions in manure-amended soil in the first fertilization stage (P<0.05) except for the experiment of 50mg/kg Zn with manure which had no significant effect on N₂O emissions (P>0.05). In the second fertilization stage, the effects of Zn on N₂O emissions were consistent under different nitrogen fertilizers:50mg/kg Zn had no significant effects (P>0.05), 500 and 1500mg/kg Zn significantly promoted N₂O emissions, while 5000mg/kg Zn had the opposite effect (P<0.05). At this stage, the ratios of cumulative N₂O emissions from the 500, 1500 and 5000mg/kg treatments to the corresponding control were 3.49, 3.13, 0.01 for manure treatments and 2.53, 2.74, 0.04 for urea treatment, respectively, indicating that the effect of Zn was much stronger in manure-amended treatments. The promotion mechanism of 500 and 1500mg/kg Zn could be the Zn-induced increase in the soil NH₄⁺-N and NO₃^--N contents as well as the abundance ratio of nirS to nosZ, and its control on the genes that are responsible for N₂O production and reduction in the denitrification process. Moreover, the 5000mg/kg Zn might impede the transformation progress of NH₄⁺-N to NO₃^--N in soil, thus reduced N₂O emissions.