摘要
本文比较了不同施氮水平对甜菜种植地和休闲地土壤中好气性细菌、放线菌和真菌数量的影响，并对土壤中的硝化细菌进行了测定。试验表明，氮肥能增加土壤中好气性细菌和硝化细菌的数量，并显著增加３０～６０ｃｍ土层中亚硝酸细菌数量，对５～１０ｃｍ、１０～３０ｃｍ和３０～６０ｃｍ土层中的硝酸细菌表现出促进作用。各施氮水平的土壤微生物总数达１×１０￣８个／ｇ干土以上。其中细菌为主要类群，约占９０％以上，其次为放线菌和真菌。在甜菜定苗前和收获期，５～３０ｃｍ土层中微生物总数顺序为施用Ｎ＿（１２０）＞Ｎ＿（１８０）＞Ｎ＿０，与甜菜的产量呈极显著正相关（ｒ＝０．９２８）．
he numbers of bacteria,actinomycctes,fungi,nitrobacter and nitrosomonas in soil of beetfield with diferent amount of nitrogenous fertilizer in April,June,August and October werestudied.Results obtained showed that the numbers of bacteria and nitrifiers were increased byusing nitrogenous fertilizer,especially those of nitrobacters and nitrosomonas in 30～60 cm soil.The microbes were more than 1 × 10￣8 per gram of dry soil with different nitrogen fertilizertreatments,among which bacteria were dominant, amounting to more than 90 %,and thenactinomycetes and fungi.There was significantly correlation(r=0.928)between beet yields andthe microbes in 5～30 cm soil in April and October
