外源氮对滨海围垦稻田土壤N_(2)O还原速率的影响机制研究

Effects of exogenous nitrogen on N_(2)O reduction rate in coastal paddy soil

滨海湿地位于海陆交错带,具有很高的生态价值;近百年来的人类活动深刻改变了湿地土壤的N_(2)O排放通量。为探明外源氮对滨海围垦稻田土壤N_(2)O还原潜力的影响,选取长江口崇明岛东滩芦苇湿地和围垦区不同围垦年限(19、27、51、86年)的稻田土壤为研究对象,添加不同形态外源氮后研究湿地土壤N_(2)O还原速率的变化情况。结果表明,无氮添加条件下芦苇湿地土壤N_(2)O还原速率最高,为36.6μg·g^(-1)·d^(-1),相比围垦19年稻田土壤提高了103%;添加硝态氮条件下围垦86年稻田土壤N_(2)O还原速率最高,是围垦19年稻田土壤的3.9倍,添加铵态氮和硝态氮条件下稻田土壤N_(2)O还原速率年增长率分别为0.37和0.69μg·g^(-1)·d^(-1)·年^(-1),比无氮处理分别高出140%和343%。对于同一样地土壤而言,外源氮输入对其N_(2)O还原速率的影响效应各异。其中,与无氮对照相比,添加铵态氮条件下芦苇湿地土壤的N_(2)O还原速率降低了32%,而添加硝态氮条件下围垦86年稻田土壤的N_(2)O还原速率增加了91%。相关性分析发现,稻田N_(2)O还原速率与土壤有机碳、总氮呈显著正相关,而与电导率、SO_(4)^(2-)呈显著负相关。因此,在围垦区水稻生产中,不同形态氮肥施用对稻田土壤的N_(2)O还原过程产生重要的影响效应。

The coastal wetland which is located in the marine-terrestrial interlaced zone,has high ecological values.In recent hundred years,human activities have profoundly changed the N_(2)O flux of coastal wetlands.In order to explore the effect of exogenous nitrogen on potential of N_(2)O reduction in the coastal wetlands,the variation of N_(2)O reduction rate was studied in reed wetland in Chongming Island,Yangtze River Estuary and reclaimed paddy field with different reclamation years(19,27,51 and 86 years)after adding different exogenous nitrogen.The results showed that the reduction rate of N_(2)O in the reed wetland soil was the highest under the condition of no nitrogen addition with value of 36.6μg·g-1·d-1,which was 103%higher than that in the paddy field with 19 reclamation years.Under the condition of adding nitrate nitrogen,the N_(2)O reduction rate of the paddy field with 86 reclamation years was the highest,which was 3.9 times that of the paddy field with 19 reclamation years.Under the condition of ammonium nitrogen and nitrate nitrogen addition,the annual growth of N_(2)O reduction rate were 0.37 and 0.69μg·g^(-1)·d^(-1)·yr^(-1),respectively,which were 140%and 343%higher than that in no nitrogen treatment.For the same soil,the effect of exogenous nitrogen input on N_(2)O reduction rate was different.The N_(2)O reduction rate of reed wetland soil under ammonium nitrogen addition was 32%lower than that of no nitrogen treatment,whereas the rate of the paddy field with 86 reclamation years soil increased by 91%under nitrate nitrogen addition.The correlation analysis showed that N_(2)O reduction rate was positively correlated with soil organic carbon and total nitrogen,but negatively correlated with soil conductivity and sulfate.Therefore,in the rice production in the reclamation area,different forms of nitrogen fertilizer application have an important effect on N_(2)O reduction process of coastal paddy soils.