Characteristics of nitrogen uptake, utilization and translocation in the indica-japonica hybrid rice of Yongyou series

Objectives The objective of this study was to evaluate the nitrogen (N) uptake, utilization efficiency and translocation of the indica-japonica hybrid rice of Yongyou series and to identify the characteristics of their relationship with yield formation.

Methods Seven indica-japonica hybrid rice of Yongyou series cultivars, two japonica rice cultivars and two hybrid indica rice cultivars were used as experimental material in 2013-2014. The characteristics of N content and N accumulation at the main growth stages, periodical N accumulation and periodical N uptake rate, N contents and ratios of N accumulation and translocation at the heading and maturity stages, N utilization efficiency were analyzed systematically.

Results The N content and N accumulation of indica-japonica hybrid rice of Yongyou series were 1.47% and 202.67 kg/hm² in heading stage, 1.31% and 257.23 kg/hm² in maturity stage, which were higher than other two control types. The highest periodical N accumulation was 107.63 kg/hm², with the highest proportion in total and periodical N uptake rate of 41.84% and 2.73 kg/(hm²·d) for the indica japonica cultivars in jointing to heading stage. The N contents of stem-sheath and leaf were 1.19% and 2.34% in heading stage, 0.75% and 1.58% in maturity stage, which were higher than other two control types. The proportions of N accumulation in stem-sheath and leaf were 43.92% and 43.87% in heading stage, 16.44% and 17.44% in maturity stage, which were significantly larger than the hybrid indica rice. The N translocation amount was larger, but the apparent transport rate and transport contribution rate were low, and net N absorbed conversion rate after heading was 32.06%, which was significantly higher than the two contrast types. N uptake per 100 kg of grain was 2.29 kg and partial factor productivity of applied N was 37.54 kg/kg, which were higher than the two control types. N utilization efficiency for grain, N utilization efficiency for biomass production and N harvesting index were lower.

Conclusions The indica-japonica hybrid rice of Yongyou series accumulate enough N at transplanting-jointing stage, and increase the proportion of jointing-heading stage and heading-maturity stage. The N translocation amount in the stem-sheath and leaves from the heading to the maturity of the indica-japonica hybrid rice of Yongyou series is large. But the apparent N translocation rate and N translocation conversion rate are low. The advantage of net N accumulation after heading stage is obvious, which can meet the demand for N in grain.