肥料氮的去向和残留氮的转化方面的知识是拟定合理施肥制度的必要根据。为了解不同肥料对土壤氮素肥力的影响,我们于1981年起,以~(15)N标记的硫铵、紫云英、田菁和绿萍为供试物料,通过连续两年的田间微区试验,研究了这些肥料的残留氮的数量和有效性。试验在江苏省望亭一块实行二年五熟水旱轮作制 Knowledge of the whereabouts of fertilizer nitrogen and the conversion of residual nitrogen is a necessary basis for developing a rational system of fertilization. In order to understand the effect of different fertilizers on soil nitrogen fertility, we started from 1981 with ~ (15) N labeled ammonium sulfate, milk vetch, Zone experiments were conducted to study the amount and effectiveness of residual nitrogen in these fertilizers. Test in Jiangsu Province Wangting a five-year implementation of two rounds of crop rotation system