NaCl对粉壤土氨挥发及硝化、反硝化的影响

Effect of NaCl on Ammonia Volatilization,Nitrification and Denitrification in Silt Loam Soil

采用室内恒温密闭培养法,以北京地区耕作层典型粉壤土为对象,研究NaCl对土壤氨挥发、硝化与反硝化过程的影响。实验设置了4个不同盐分(NaCl浓度分别为2%、3%、5%、8%)处理和1个对照处理(不加NaCl),并在土壤中加入一定量的(NH4)2SO4,在28℃恒温培养箱中进行为期30d的培养实验。结果表明,盐分可促进土壤NH3的挥发,盐分浓度为2%～8%的处理,其土壤NH3挥发量比对照处理高9.96%～21.40%,且随盐分含量增加,土壤NH3挥发损失越大。在硝化作用初期,盐分对土壤硝化具有一定的促进作用,当硝化时间较长,盐分浓度低于3%时,盐分对土壤硝化无影响;当盐分浓度大于3%时,盐分对土壤硝化具有一定的抑制;当盐分浓度为8%时,累积硝化量比对照低15.17%。盐分浓度为2%～8%的处理,其反硝化量比对照处理低11.55%～27.34%,且盐分浓度在3%以内时,盐分对土壤反硝化的抑制作用随盐分浓度增大而增强;当盐分浓度高于3%时,盐分对土壤反硝化的抑制作用与盐分浓度无关。

Using laboratory incubation method, an experiment was carried out to investigate the effect of sodium chloride （NaCl） on ammonia volatilization, nitrification and denitrification in silt loam soil, one of the typical soils in the cultivated layer of Beijing area. The soil was amended by adding （NH4）2SO4 solutions with NaCl concentrations of 0, 2%, 3%, 5%, and 8%, respectively, and then incubated at 28 ℃ for 30 d. Compared with the treatment without salinity, ammonia volatilization increased 9.96%-21.40% under the treatments with NaCl concentration of 2% to 8%, and ammonia volatilization increased with the increase of salinity level. Nitrification in soil was enhanced by salinity at the initial incubation stage, but was not influenced by salinity with the concentration of less than or equal to 3% for a relatively long period of incubation. The nitrification was inhibited by NaCl over 3% to some extent, with the cumulative nitrification reduced by 15.17% for the treatment with NaCl concentration of 8%. Total denitrification was reduced by 11.55%-27.34% for the treatments with NaCl concentration of 2% to 8%. The inhibition of denitrification in soil increased with the salinity level when NaCl concentration was less than or equal to 3%, but was independent of salinity level at NaCl concentration over 3%.