Selection for phosphorus (P)-efficient genotypes and investigation of physiological mechanisms for P-use efficiency in maize has mainly been conducted at the seedling stage under controlled greenhouse conditions.Few studies have analyzed characteristics of plant growth and yield formation in response to low-P stress over the whole growth period under field conditions.In the present study,two maize inbred lines with contrasting yield performances under low-P stress in the field were used to compare plant growth,P uptake and translocation,and yield formation.Phosphorus accumulation in the P-efficient line 154 was similar to that of line 153 under high-P.Under low-P,however,P uptake in line 154 was three times greater than that in line 153.Correspondingly,P-efficient line 154 had a significantly higher yield than P-inefficient line 153 under low-P conditions (Olsen-P=1.60 mg kg-1),but not under high-P conditions (Olsen-P=14.98 mg kg-1).The yield difference was mainly due to differences in the number of ears per m2,that is,P-efficient line 154 formed many more ears under low-P conditions than P-inefficient line 153.Ear abortion rate was 53％ in the P-inefficient line 153,while in line 154,it was only 30％.Low-P stress reduced leaf appearance,and delayed anthesis and the silking stage,but increased the anthesis-silking interval (ASI) to a similar extent in both lines.The maximum leaf area per plant at silking stage was higher in P-efficient line 154 than in P-inefficient line 153 under both P conditions.It is concluded that low-P stress causes intense intraspecific competition for limited P resources in the field condition which gives rise to plant-to-plant non-uniformity,resulting in a higher proportion of barren plants.As soon as an ear was formed in the plant,P in the plant is efficiently reutilized for kernel development.