Photosynthetic efficiency and dry matter accumulation are essential for achieving high rice yields, yet conventional controlled-release fertilizers often fail to synchronize nitrogen (N) supply with crop demand. In this study, we evaluated a novel double core–shell controlled-release urea (DCSCRU) designed to align with the bimodal N uptake pattern of rice. A two-year field experiment was conducted to compare DCSCRU at three application rates (180, 225, and 270 kg N ha⁻¹) with conventional urea and conventional controlled-release urea (both at 270 kg N ha⁻¹). DCSCRU exhibited a distinct biphasic N release profile, with a rapid initial release peaking at 1.60% d ⁻¹ on day 10 to meet early vegetative demand, followed by a second peak (1.85% d⁻¹ on day 45) supporting reproductive development. Compared with conventional urea, DCSCRU treatments significantly improved photosynthetic efficiency and dry matter accumulation during critical growth stages. The 270 kg N ha⁻¹ DCSCRU treatment achieved a grain yield exceeding 11.50 × 10³ kg ha⁻¹, substantially higher than that of conventional urea. Notably, the 225 kg N ha⁻¹ DCSCRU treatment produced a comparable yield (10.90 × 10³ kg ha⁻¹) to that of the conventional urea treatment (10.83 × 10³ kg ha⁻¹), indicating the potential to reduce N input by 16.7% without compromising yield. The enhanced physiological performance was attributed to improved N availability and optimized canopy function. These findings highlight DCSCRU as a promising strategy for high-yield, resource-efficient, and environmentally sustainable rice production.

Synergizing iron nutrition and rice quality is essential for the development of integrated high-quality rice. In this study, a two-year field experiment was conducted to investigate the influence of ferric oxide nanoparticles (Fe₂O₃ NPs) foliar spraying on rice yield, quality, and iron bioavailability, with spraying water as the control (CK). Our results demonstrate that Fe₂O₃ NPs foliar application increase grain yield by 1.22–3.97% for the improved filled grain rate and 1000-grain weight, essentially attributed to improved net photosynthetic rate and SPAD value after heading. In addition, Fe₂O₃ NPs application achieved a higher rate of brown rice, polished rice, and head rice, and decreased chalkiness grain rate and chalkiness degree. Rice taste value treated with Fe₂O₃ NPs application was notably increased by 2.75–9.43% compared to CK, respectively, which is also reflected in the superior breakdown value (5.85–15.18%) and inferior setback value (12.38–28.19%). Meanwhile, foliar spraying Fe₂O₃ NPs significantly increased the iron content (16.97–58.74% and 26.48–94.01%) and proportion (2.90–5.35% and 13.10–26.44%), while they decreased the molar ratio of phytate to Fe (19.70–33.67% and 31.55–45.77%) in brown rice and polished rice, increasing iron bioavailability. Our findings indicate that Fe₂O₃ NPs can be effectively applied as a foliar fertilizer to enhance rice yield, quality, and iron nutrition.

Improving rice yield and optimizing rice quality are of great significance for ensuring food security. In modern rice production, mechanical transplanting has become the dominant transplanting method. Precise regulation of plant spacing and row spacing contributes to the formation of different transplanting densities, which further exerts effects on photosynthetic spikelets filling, yield formation and quality development of rice. Two-year field experiments were conducted with two conventional japonica rice cultivars of contrasting yield levels under four transplanting hill spacings at a uniform row spacing of 30 cm. The results showed that rice cultivars with higher seed-setting rate with an increase ranging from 1.44 to 1.91% and larger grain weight with an increase ranging from 13.17 to 13.40% presented more prominent yield potential. In addition, high-yield rice cultivars possessed more excellent photosynthetic carbon metabolism characteristics, which effectively improved the spikelets filling process of rice kernels. Superior photosynthetic carbon metabolism characteristics were conducive to increasing head rice rate and reducing chalkiness, while maintaining the duration of spikelets filling benefited the improvement of rice taste value. Narrowing the transplanting plant spacing reduced the physiological enzyme activities in rice leaves and grains, weakened photosynthetic carbon metabolism and hindered spikelets filling, which further decreased head rice rate and protein content but increased chalkiness. Notably, rice taste value also showed an increasing trend. The taste value of superior spikelets (SSs) of the two rice cultivars increased by 1.97–5.11% and 0.98–2.60% respectively, and that of inferior spikelets (ISs) increased by 1.37–3.64% and 1.62–4.12% respectively. Reducing transplanting plant spacing also significantly increased the number of effective panicles, resulting in an increase in population spikelet number. The final yield of the two rice cultivars increased by 5.38–11.62% and 5.23–11.03% respectively.