Mechanisms and conditions of nitrite accumulation occurring in calcareous soil

【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 ammoniumureanitrate 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 ℃.