摘要： 将土壤样品置于康维皿外室,硼酸吸收液于内室,利用碱解扩散法直接测定土壤有效氮,最理想的还原剂是Devarda合金.土样、还原剂、氢氧化钠溶液的最佳配比是5克(土样):0.2克(代氏合金):5ml(1.0N NaOH溶液).30℃恒温条件下反应4小时,土壤硝态氮的还原率为90%左右,铵态氮的回收率为95%以上,并包括少量水溶性和极易在碱性条件下水解的有机态氮.上述方法所测土壤有效氮称为“改进康维法土壤碱解氮”,其与土壤N-min间的相关系数高达0.982(n=10).和一般的康维法比较,用改进康维法测定碱解氮所用时间减少5/6,并更能代表土壤供氮能力.该方法还可用于土壤N-min的简化测定.

关键词: 土壤, 有效氮, 康维法, 代氏合金还原

Abstract: The ideal reducing agent in soil available nitrogen tests by Conway Method is Devarda alloy. The optimum ratio of soil : Devarda alloy : 1.0 N NaOH solution is 5. 0g : 0.2g: 5 ml. When reaction goes on at 30℃ for 4 hours, the rate of soil N-NO3- reduction is about 90%, and the recovery rate of soil N-NH4 is about 95%. Some organic nitrogen can be measured at the same time. This method is defined as the Modified Conway method. The correlation between the value of soil available nitrogen determined by the Modified Conway Method and the soil N-min is r= 0.982 (n=10). Better in predicating soil nitrogen supplying power, the Modified Conway Method takes only 1/6 the time needed by the Conway Method. The Modified Conway Method can also be used for the measure of soil N-min.

Key words: Soil, Available nitrogen, Conway method, Devarda alloy reduction