Nitrogen uptake,utilization and rice yield in the north rimland of double-cropping rice region as affected by different nitrogen management strategies

Two early indica rice cultivars of Xiangliangyou 68 and Zaoxian 65 were used to study nitrogen uptake,utilization,yield and yield components as affected by different split N application strategies when the total nitrogen application amount was 150 kg/ha in the north rimland of double-cropping rice.Results showed that reducing N application before transplanting and at tillering stage but increasing N application at booting stage could increase rice yield and nitrogen uptake and utilization,by increasing leaf nitrogen content and SPAD in top 3 leaves during heading stage to mature stage,and increasing LAI and effective leaf area percentage.When nitrogen fertilizer was applied before transplanting(50%),tillering(25%),booting (25%),both hybrid and conventional rice cultivars had highest yield.The main benefit of postponing N fertilizer application time on yield formation was related to its improved splitting and timing of fertilizer N applications leading to a more balanced supply of N nutrition for rice growth than the common fertilizer practice,and to increase total amount of N-absorption(ANA).Nitrogen fertilizer use efficiency(NUE) increased with the percentage of panicle fertilizer,but the agronomic use efficiency of N fertilizer had better relationship with yield. It is concluded that the split application of N before transplanting(50%),at tillering stage(25%) and at booting stage(25%) is a rational N application strategy in the north rimland of double-cropping rice.