中文摘要：

以安徽郎溪耕地红壤耕层土壤为对象,采用室内恒温培养方法,研究了CO（NH2）2、（NH4）2SO4及NH4HCO33种氮肥在不同施用量条件下对土壤硝化作用及酸化过程的影响。结果表明,对照处理土壤的净硝化速率为（NO2-＋NO3-）-N 25.7μmol/（kg·d）;3种化学氮肥添加到土壤后均显著促进了土壤的硝化作用,CO（NH2）2、NH4HCO3处理土壤的净硝化速率分别为（NO2-＋NO3-）-N 51.3～189.6、50.7～149.9μmol/（kg·d）,且净硝化速率随氮肥用量增加而增加;（NH4）2SO4处理土壤的净硝化速率为（NO2-＋NO3-）-N 60.5～107.9μmol/（kg·d）,以施用量N 150 mg/kg时最大。研究同时发现,3种化学氮肥均导致土壤pH下降,CO（NH2）2、NH4HCO3处理土壤pH较对照处理分别下降0.11～0.43、0.02～0.36个pH单位,氮肥施用越多,pH值下降越大;（NH4）2SO4处理土壤pH较对照处理下降0.08～0.26个pH单位,以施用量N 150 mg/kg时下降最大,N 300 mg/kg时下降最小。统计分析表明,土壤pH与土壤中（NO2-＋NO3-）-N含量呈极显著负相关,土壤酸化速率与净硝化速率有显著的线性相关关系,说明氮肥通过硝化作用影响土壤酸度。

英文摘要：

An Ultisol from cropland in Anhui province in subtropical China was used to study the effects of urea,ammonium sulfate [（NH4）2SO4] and ammonium bicarbonate（NH4HCO3） on nitrification and acidification of the soil with incubation experiments.Nitrification increased significantly with nitrogen fertilizers added.The net nitrification rate of the control soil was（NO-2＋NO-3）-N 25.7 μmol/（kg·d）,the corresponding figures were（NO-2＋NO-3）-N 51.3-189.6,50.7-149.9 and 60.5-107.9 μmol/（kg·d） for the treatments with urea,NH4HCO3 and（NH4）2SO4 added,respectively.Greater addition of urea and NH4HCO3 led to a more increase in net nitrification rate;however,the highest net nitrification rate occurred when N 150 mg/kg soil was added for（NH4）2SO4 treatment.Meanwhile,soil pH decreased by 0.11-0.43,0.02-0.36 and 0.08-0.26 pH units for the treatments of urea,NH4HCO3 and（NH4）2SO4 compared with the control,respectively.There was a significant negative correlation between the soil pH and the content of（NO-2＋NO-3）-N.Soil acidification rate was also linearly correlated with nitrification rate,confirming that nitrification in soil was the main cause for accelerating acidification of the Ultisol.