Abstract:During 1985-1990 we conducted 4 field experiments on N, P and K to ginseng on solis of Changbai County and Gongzhuling City. All the results showed that nitrogen retarded plant growth and decreased yield of ginseng mostly at 5% sigificance level and even to the level of 1% when the rate of N doubled. By successive study, we found that the nitrate reductase acitvity (NRA) of ginseng was so low that the NO3 absorded could not be.reduced promptly and was accumulated in the tissues, and that, compared with control, the N, Si, Cu> Zn> Fe and Mn contents incrased in N fertilized ginseng tissues, P and such cations as Ca, Mg, K and Na decreased, and the respiration rate of ginseng shoot accelerated (44.8% over control) by N top dressing. These have ever been described as N toxicity in literature. In this paper we tentatively refer to this physiological toxicity as ‘N excess',which is caused by the fact that the N supply is too much to transfer instantly by low NRA.