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.