石灰性土壤中亚硝态氮的累积机理和条件

Mechanisms and conditions of nitrite accumulation occurring in calcareous soil

【目的】探讨石灰性土壤中亚硝态氮的累积机理和条件,为氮素管理和环境保护提供依据。【方法】采用室内培养的方法,探讨了不同氮肥种类、氮肥用量、土壤水分含量和温度对土壤亚硝态氮产生和累积的影响。【结果】在培养条件下（土壤水分含量为田间持水量（WHC）的60%,温度为25℃）,硝态氮肥处理的土壤中几乎未检测到亚硝态氮;3种铵态氮肥处理均有不同程度的亚硝态氮累积,土壤中亚硝态氮含量依次为硫酸铵〉尿素〉硝酸铵;土壤中亚硝态氮含量与铵态氮含量呈极显著正相关,与硝化速率呈极显著负相关。土壤中亚硝态氮含量随氮肥施用量的增加而增大;随土壤水分含量的增加而上升。培养温度为45℃时,土壤亚硝态氮含量最小;培养温度为25℃和35℃时,土壤亚硝态氮含量差异较小,且均高于45℃时。土壤中亚硝态氮累积总量与氮肥用量和土壤水分含量均呈显著直线正相关;亚硝态氮最大含量与土壤水分含量呈显著直线正相关,出现在硝化作用5~10 d后。【结论】在该试验培养条件下,硝化过程是石灰性土壤亚硝态氮的来源,土壤亚硝态氮累积量随氮肥施用量和土壤水分含量的增加而增大,其最适宜累积的温度为25℃。

【Objective】The research studied the mechanisms and conditions of nitrite accumulation,which is essential for nitrogen management and environmental protection.【Method】In the laboratory experiments different nitrogen fertilizers,fertilizer rates,various soil moisture contents,and temperature regimes were applied in the same incubation conditions to identify the nitrite production and accumulation in calcareous soil.【Result】In the experimental conditions（soil moisture content：60% of water hold capacity,25 ℃）,there was not any nitrite found in sodium nitrate treatment,while nitrite accumulation appeared for all three ammonium nitrogen fertilizers,nitrite content in soil was in the order as sulfate ammonium〉urea〉nitrate ammonium.Soil nitrite concentration was positively correlated with ammonia content and negatively agreed with the nitrification rate for three tested ammonium fertilizers.Meanwhile,soil nitrite concentration descended with the increase of fertilizer use amount and soil moisture.Nitrite production was small under incubation temperature of 45 ℃,there wasn＇t any significant difference between incubation temperature of 25 ℃ and 35 ℃,but soil nitrite concentration was bigger than soil incubated at 45 ℃.The total nitrite accumulated amount during incubation period was in significant agreement with nitrogen rates and soil moisture.The maximum nitrite concentration in soil was remarkably correlated with soil moisture content,and appeared 5-10 days after fertilizer application.【Conclusion】Under the given incubation conditions（soil moisture content：60% of water hold capacity,25 ℃） nitrification process was the main cause for nitrite production,the nitrite accumulated amount increased with the rise of soil moisture,and the optimum incubation temperature was 25 ℃.