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A field experiment was conducted with 24 indica-japonica 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 7.91–7.99 t hm–2 from heading to maturity, which was the highest in three types, and its dry matter accumulation was more than 21.15–21.46 t 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 100 kg grain), all the other nitrogen utilization indexes of HM type were higher than that of MM type.

Background Nitrogen management of crops, especially when mid-stage nitrogen is applied, is a key factor affecting the yield and grain quality of rice (Oryza sativa). Here, the timing of mid-stage nitrogen application was evaluated for its effect on rice grain quality by assessing the morphological structure and physicochemical properties of starch from two japonica rice cultivars growing in fields (Nangeng 9108 and Nangeng 5055). Results The experiment was arranged in a split-plot design, with the two rice cultivars as the main plot factor and three timings of mid-stage nitrogen application as the within-plot factor. Briefly, three applications were made: at the emergence of the top-sixth-leaf (ahead), the top-fourth-leaf (normal), and the top-second-leaf (delayed) of the main stem. Delaying mid-stage nitrogen application caused the starch granule surface to become uneven and significantly reduced its particle size, whereas it increased the polished rice rate, chalkiness degree, and protein content. Furthermore, the apparent amylose content decreased with a delay in mid-stage nitrogen application, thereby resulting in higher relative crystallinity, swelling power, water solubility, gelatinization enthalpy, and low retrogradation. Finally, we also found that delaying this nitrogen application lowered the characteristic values of rice flour viscosities, leading to cooking quality deterioration. Conclusion These results therefore suggest that delaying mid-stage nitrogen application enhances the processing and nutritional qualities of japonica rice but evidently has an adverse effect upon its appearance and cooking qualities. © 2020 Society of Chemical Industry.

There is limited information about the influence of slow or controlled release fertilizer (S/CRF) on rice yield and quality. In this study, japonica rice cultivar Nanjing 9108 was used to study the effects of three different S/CRFs (polymer-coated urea (PCU), sulfur-coated urea (SCU), and urea formaldehyde (UF)) and two fertilization modes (both S/CRF and common urea (CU) as basal fertilizer, S/CRF as basal and CU as tillering fertilizer) on rice yield and quality. CU only was applied separately as control (CK). Results showed that, rice grain yield, chalky kernel rate, chalky area, overall chalkiness, and the content of gliadin, glutenin, and protein, all showed the trends of UF>PCU>SCU within the same fertilization mode, and showed the trends of S/CRF as basal and CU as tillering fertilizer>both S/CRF and CU as basal fertilizer within the same type of S/CRF. In contrast, the contents of amylose, amylopectin, and starch, as well as taste value, and peak and hot viscosity showed trends of SCU>PCU>UF, and the trends of both S/CRF and CU as basal fertilizer>S/CRF as basal and CU as tillering fertilizer. Among S/CRF treatments and fertilization modes, taste values of cooked rice were positively correlated with amylose, amylopectin, and starch contents, as well as gel consistency, peak viscosity, hot viscosity, and cool viscosity, while negatively correlated with globulin, gliadin, glutenin, and protein contents. The types of S/CRF and fertilization modes are important for improving rice yield and quality. Compared to CK, higher yield and similar quality of rice was achieved with UF as basal and CU as tillering fertilizer, and similar yield with improved appearance and eating and cooking quality of rice was achieved with either both UF and CU as basal fertilizer, or PCU as basal and CU as tillering fertilizer.