镉胁迫对不同植烟土壤硝化速率及N2O排放的影响

为明确镉(Cd)胁迫对不同植烟土壤的硝化速率及氧化亚氮(N₂O)排放的影响,采用外源镉添加试验,设置两个 Cd浓度梯度(10和100mg/kg),以探究Cd胁迫下中性(中性土1和2)和酸性(酸性土1和2)植烟土壤的净硝化速率以及N₂O排放特征。结果表明:1)随培养时间增加,植烟土壤铵态氮含量逐渐减少,而硝态氮含量逐渐增加,且低Cd胁迫和高Cd胁迫均未显著改变这一变化趋势;2)植烟土壤净硝化速率在培养前期(1~7 d)发生较大波动变化,Cd胁迫明显增加了酸性土1在第1天的净硝化速率;3)整体上各处理酸性土的N₂O排放速率和累积排放量高于中性土,高Cd胁迫增加了酸性土1的N₂O初始排放速率,培养结束后酸性土1的N₂O累积排放量达355.42μg/kg;4)各植烟土壤N₂O排放速率和累积排放量与土壤pH和全氮含量极显著负相关,而与有机质和铵态氮含量极显著正相关。本研究结果表明植烟土壤的N₂O排放受土壤酸碱性和氮底物的影响,酸性土的N₂O累积排放量高于中性土,且高Cd胁迫增加其N₂O排放量,后续可通过土壤酸化改良以达到N₂O减排目的。

Effects of Cd Stress on Nitrification Rate and N2O Emission in Tobacco Planting Soils

In order to determine the effect of cadmium stress on nitrification rate and N₂O emission traits of different tobacco planting soils,an incubation experiment of acid and neutral soils under two concentrations (10 and 100 mg/kg) of Cd addition were conducted. The results showed that,1) The concentration of ammonium in acid and neutral tobacco soils decreased gradually with the extension of incubation time,while the concentration of nitrate increased throughout the whole incubation periods,and this tendency was not affected by low and high concentrations of Cd stress;2) Soil net nitrification rate fluctuated strongly during the 1-7 d of incubation and Cd stress could stimulate net nitrification rate of acid soil type 1 on the 1st day;3) The maximum of N₂O emission rate and cumulative emission of acid soils were higher than that of neutral soils in general,and the high Cd stress could stimulate the initial N₂O emission rate of acid soil 1,and the cumulative N₂O emission of acid soil 1 was 355.42 μg/kg at the end of the incubation;4) Soil pH and total nitrogen had significantly negative correlations with soil N₂O emission rate and cumulative emission,but soil organic matter and ammonium had significantly positive correlations with soil N₂O emission rate and the cumulative emission.These results indicated that N₂O emission of tobacco planting soils was affected by soil pH and N substrate.The N₂O cumulative emission of acid soils was much higher than neutral soils and they could be stimulated by the high Cd stress.So,the reduction of N₂O emission could be achieved by improving soil acidification in the future.