Differences in yield and nitrogen absorption and utilization of <italic>indica-japonica</italic> hybrid rice varieties of Yongyou series

Abstract

<p indent=0mm>A field experiment was conducted with 24 <italic>indica-japonica</italic> hybrid rice varieties (lines) of Yongyou series, from which three types (high yield and high AE (agronomic nitrogen use efficiency) [HH], high yield and medium AE [HM], medium yield and medium AE [MM]) were selected to explore the characteristics of varieties with high yield and high AE. The yield of HH type was 4.04%–4.38% and 13.37%–13.41% higher than that of HM type and MM type respectively, owing to the larger number of total spikelets, which was 5.87×10⁸–6.20×10⁸ hm^–2. Compared with HM and MM type, HH type had a high percentage of tiller rate, which was 68.83%–70.05%. The LAI of HH type was maximum at heading stage and declined slowly after heading. As a result, the LAI of HH type was above 3.85 at maturity stage. The dry matter accumulation of HH type was <sc>7.91–7.99 t</sc> hm^–2 from heading to maturity, which was the highest in three types, and its dry matter accumulation was more than <sc>21.15–21.46 t</sc> hm^–2 in the whole growth period. The total nitrogen uptake of HH type showed 5.07%–5.14% and 4.50%–5.96% increase than that of HM type and MM type respectively at maturity stage. The nitrogen sbsorption rate from jointing to heading stage and from heading to maturity stage showed HH type > HM type > MM type, as well as NTSH (N transportation from stem after heading), NIPH (N increase in panicle after heading) and NHI (N harvest index). HH type had the highest NRE (nitrogen recovery use efficiency), AE, PE (physiological nitrogen use efficiency) and PFP (partial factor productivity of applied N). Expect for NRE and NRG (nitrogen requirement for <sc>100 kg</sc> grain), all the other nitrogen utilization indexes of HM type were higher than that of MM type.