The increase in atmospheric nitrogen(N)deposition is an important aspect of global change.Numerous studies have shown that long-term N deposition would increase N:phosphorus(P)of ecosystems,leading to the increase of P limitation in ecosystems and hence accelerating the P demand of plants.In this paper,we conducted a 2-year(2013-2014)N:P supply(10g·m~(-2)·a~(-1) N combined with different P amounts)pot-cultured experiment for a common desert steppe species Pennisetum centrasiaticum.We determined the effects of N:P supply on C:N:P stoichiometry in both soil and P.centrasiaticum(leaves and belowground parts).We also analyzed the indication of C:N:P stoichiometry for the growth and nutrient utilization of P.centrasiaticum.The results showed that:(1)reducing N:P supply(thereby increasing P fertilization)significantly decreased C:P and N:P in both soils and P.centrasiaticum,alleviating P limitation for the growth of P.centrasiaticum,and further promoting the biomass accumulation of P.centrasiaticum.(2)The gradual decrease of N:P supply would shift P limitation to N limitation for P.centrasiaticum.(3)In this case,P.centrasiaticumincreased the ability of N resorption from its senescing leaves,which reduced its dependence on soil N pool,reflecting the adaptation of P.centrasiaticum to N-limited environments.Our results suggest that appropriate artificial P addition could adjust the stoichiometry balance of C,N,and P between soil and plants,alleviate the pressure between soil P supply and plant P demand,and thus mitigating N-induced increase of P limitation.The results could provide scientific guidance for the adaptive management of fragile ecosystems under increasing N deposition.