Rational nitrogen(N)fertilizer application rate and assignment on rhizome lotus were studied by field experiments.Results showed that under an almost equal theoretical rhizome lotus yield of 29 000~32 000 kg/hm2 ,the critical value of N application rate that determined by linear+plateau model(350~417 kg/hm2)was greatly lower than the optimum economic N application rate that determined by quadratic model(469~604 kg/hm2).Taken the present status of rhizome lotus production,fertilization of farmer practice and lotus field soil N fertility into consideration,rational N application rates on rhizome lotus in Hubei province were suggested to be 300~375 kg/hm2.Two rational N fertilizer assignment styles were proposed,one was “40% basal fertilizer+20% top dressing in early June+40% top dressing in late June or early July”,the other was “60% top dressing in early or middle May+20% top dressing in early June+20% top dressing in late June or early July”.The former was suitable for lotus field where the basal fertilizers were applied just before rhizome lotus transplanting in early or middle April,and the latter was suitable for lotus field where the first fertilizers application was conducted after 2~3 standing leaves developed.