盐分对土壤氨挥发与反硝化速率的影响

Effects of Salinity on Soil Ammonia Volatilization and Denitrification Rates

海涂盐碱地是重要的土地后备资源,但其土壤结构性差,氮肥利用效率低,加之土壤钠盐含量季节与年际变化明显,土壤氮素循环过程具有显著特色。盐分作为氮素循环的重要影响因子,进一步明确其对氨挥发和反硝化速率的影响规律具有重要理论价值。通过培养试验,设置<1(即不做盐分处理,CK)、1、2、4和10 g·kg^(-1)共5个土壤盐分梯度,对氨挥发、反硝化速率及相关水土环境因子进行测定分析,研究盐分变化对海涂土壤氨挥发和反硝化的影响规律。结果表明,高盐分梯度减弱了土壤对NH_(4)^(+)的吸附能力,促进NH_(4)^(+)向水体释放,同时影响pH及氮素浓度,提供碱性环境,促进NH_(4)^(+)向NH 3的转化,显著增大氨挥发速率。土壤反硝化速率随盐度升高而显著降低。nirK和nosZ基因型反硝化细菌丰度与盐度(即Na+浓度)呈显著负相关关系,高盐度抑制微生物活性,降低土壤反硝化速率。

The coastal area is an important land reserve.However,the saline-alkaline soil in coastal area is characterized by poor soil structure,low nitrogen use efficiency,and obviously seasonal and annual variation in sodium salinity changes which has resulted in an unique soil nitrogen cycle process.The sodium salinity is an important factor influencing the nitrogen cycle,so it is of great theoretical value to clarify its influence on ammonia volatilization and denitrification rate.In this study,cultivation experiments were established with five sodium salinity gradient,namely<1,1,2,4,and 10 g·kg^(-1),to study the effects of salinity on ammonia volatilization and denitrification in coastal soil.Ammonia volatilization and denitrification rates and related water and soil environmental parameters were measured.The results show that high salinity gradient not only reduced the NH_(4)^(+)adsorption capacity of soil and promoted the release of NH_(4)^(+)into the water,but also affected pH and nitrogen concentration.The soil environment became alkaline.Alkaline environment promoted the conversion of NH_(4)^(+)to NH 3,and the ammonia volatilization rate increased significantly.Soil denitrification rate decreased obviously with increasing salinity.The study also found a significant negative correlation between salinity(Na+concentration)and abundance of denitrifying bacteria(nirK and nosZ genotypes).High salinity inhibited microbial activity and reduced denitrification rate.