Yanju Yang

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.

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, eating quality, and zinc (Zn) nutrition is crucial to meet the growing demand for high-quality and nutritious food, while zinc itself plays a pivotal role in rice growth and quality formation. In this two-year field study, we investigated the effects of zinc oxide nanoparticles (ZnO NPs) one-time foliar application at 5, 10, and 20 mg L⁻¹ during the gestation stage on grain yield, rice quality, and zinc biofortification. Although some year-to-year variations and year × treatment interaction in the magnitude of these effects were observed, the positive responses to ZnO NPs were consistent across the two years. Results showed that ZnO NPs application increased grain yield by 1.40–4.62%, mainly supported by enhanced net photosynthetic rate and SPAD values after heading. Meanwhile, ZnO NPs significantly enhanced taste value (1.61–7.22%) and breakdown value (5.36–15.63%), while reducing chalkiness rate (5.73–18.62%), chalkiness degree (11.57–27.18%), amylose content (3.72–6.76%), and setback value (8.98–24.53%). Additionally, ZnO NPs markedly increased the zinc content (23.73–85.10% in brown rice; 29.07–103.07% in polished rice) and reduced the phytic acid to zinc molar ratio by 18.46–48.39%, improving zinc enrichment and bioavailability. These findings suggest that ZnO NPs foliar application is effective to simultaneously enhance grain productivity, rice quality, and zinc density.

Zinc (Zn) oxide nanoparticles (ZnO NPs) have been increasingly utilized in agriculture as an innovative Zn fertilizer, prompting numerous studies to assess their impact on plant growth. However, research on the optimal application methods and dosages of ZnO NPs in rice remains limited. In this study, various basal application dosages (0, 3.75, 7.5, 15, 30 and 60 kg hm⁻²) of ZnO NPs on rice yield, rice quality, and Zn content and distribution in grains were investigated using field experiments in the rice growing seasons of 2022 and 2023. Control experiments were also conducted, including treatments without Zn application and those with ZnSO₄ applied at the same Zn dosage. Results showed that ZnO NP and ZnSO₄ applications led to an increase in rice grain yields in the range of 0.34–0.50 t hm⁻² and 0.06–0.40 t hm⁻², respectively, over the two-year experiment compared to the treatment without Zn application. Furthermore, ZnO NPs improved rice quality by enhancing the head rice rate, reducing chalky grain percentage, and improving taste value and rice breakdown. The application of ZnO NPs significantly elevated Zn content in both milled and brown rice compared with the control. In 2022, Zn content in milled rice increased from 20.79% to 41.67% and in brown rice from 25.20% to 47.31%. In 2023, the increase ranged from 12.18% to 32.18% in milled rice and from 17.68% to 38.66% in brown rice. However, the utilization efficiency of ZnO NPs decreased from 7.02% to 1.26% as the application dosage increased from 3.75 kg hm⁻² to 60 kg hm⁻². Despite this decrease, the utilization efficiency of ZnO NPs remained higher than that of ZnSO₄ at the same Zn dosages. Considering yield, rice quality, Zn fertilizer utilization, and Zn accumulation, a basal application dosage of 7.5–30 kg hm⁻² of ZnO NPs is optimal for improving rice yield, rice quality, and Zn accumulation. This study effectively demonstrated that ZnO NPs could serve as a highly efficient fertilizer for synergistically enhancing rice yield, rice quality, and Zn content in the edible grain fraction.

Nitrous oxide (N₂O) emissions from paddy soils, particularly from the rice rhizosphere, significantly contribute to agricultural greenhouse gas outputs. This study explores N₂O emission dynamics in rhizosphere (R) and non-rhizosphere (NR) soils from two distinct paddy types (JR and YC) during the primary rice growth stages (tillering, jointing, heading, and grain-filling). Cumulative N₂O emissions were measured at 688.56, 762.90, 831.20, and 1072.32 µg N kg^-1 for JR-NR, JR-R, YC-NR, and YC-R, respectively. Notably, JR-R and YC-R exhibited increases in cumulative N₂O emissions by up to 20.04% and 28.23%, respectively, compared to their NR counterparts at different growth stages. These enhanced emissions were primarily associated with microbial genera Nitrosospira and Nitrosospirae, and influenced by factors such as electrical conductivity (EC) and available potassium (AK). The soil organic carbon to total nitrogen ratio (C/N) was a key determinant influencing Nitrosospira abundance. Additionally, nitrification inhibitors (NIs) demonstrated a substantial reduction in N₂O emissions, with a decrease of 92.37% in JR-R and 91.93% in YC-R at selected growth stages, showing more pronounced effects compared to NR soils. These findings highlight the efficacy of NIs in significantly mitigating N₂O emissions, particularly in rhizosphere soils. Variations in the efficiency of NIs across different soil types and growth stages suggest that optimizing application timing and developing tailored soil-specific strategies could further enhance the effectiveness of NIs in mitigating N₂O emissions from paddy fields. This research provides essential insights for developing targeted mitigation strategies to reduce N₂O emissions in rice cultivation and contributes to sustainable agricultural practices.

Zinc (Zn) is a critical co-factor for enzymes involved in photosynthesis, delaying leaf senescence and enhancing photosynthetic efficiency. Supplementing rice leaves with Zn can improve yield, quality, and Zn content in edible parts, addressing food security and micronutrient deficiencies. In this study, we evaluated the effects of spraying Zn oxide nanoparticles (ZnO NPs) (0, 5, 10, and 20 mg L⁻¹) at the rice panicle initiation stage on photosynthesis, yield, and grain quality through a two-year field experiment. Results showed that foliar application of ZnO NPs at the panicle initiation stage increased the leaf area index, net photosynthetic rate, and photosynthetic potential, leading to a 1.5–6.4% increase in grain yield through a higher grain filling rate and 1000-grain weight. ZnO NPs also delayed leaf senescence and prolonged the duration of active photosynthesis, which significantly contributed to higher biomass production and improved grain filling, further enhancing yield. Additionally, the enhancement in photosynthetic efficiency and delayed senescence promoted the production of high-quality grains. ZnO NPs improved rice appearance quality by reducing the chalkiness grain rate and degree. The rice tasting value increased by 3.3–7.0%, reflecting improvements in appearance, viscosity, and balance, along with reductions in hardness. ZnO NPs raised peak viscosity and breakdown values while lowering setback values. Furthermore, ZnO NPs significantly increased Zn content in brown and milled rice by 13.8–56.0% and 20.1–78.6%, respectively, and improved Zn bioavailability by reducing the phytate-to-zinc molar ratio. These findings highlight the potential of ZnO NPs as a sustainable nanotechnology-based approach to simultaneously improve rice productivity, quality, and nutritional value, offering a promising solution for addressing food security and micronutrient deficiency in rice-based diets.

Zinc oxide nanoparticles (ZnO NPs) have been applied widely in agriculture, and many studies were conducted to evaluate the effect of ZnO NPs on plant growth. So far, few studies have been investigated with regard to the potential effect of ZnO NPs on cereal yield formation or Zn content in grains. Herein, we used a pot experiment, which was conducted involving five dosages of Zn (0.3, 0.6, 1.2, 2.4, and 4.8 g Zn pot⁻¹), to evaluate the impacts which ZnO NPs made in rice yield, dry matter accumulation, rice quality and grain Zn contents. The results demonstrated that ZnO NPs increased the production of grain, dry matter accumulation and particulate Zn content. Compared with control treatment, ZnO NPs application presented higher rice yield with more panicle number (4.83–13.14%), spikelets per panicle (4.81–10.69%), 1000-grain weight (3.82–6.62%) and filled grain rate (0.28–2.36%). Additionally, the dry jointing, heading and mature periods, LAI, SPAD values, and photosynthetic potentials of ZnO NPs were all significantly higher relative to treatment without ZnO NPs. The more photosynthetic substances and higher dry matter accumulated in the whole rice growing stage resulted in higher rice grain yield. Furthermore, ZnO NPs increased brown rice rate, milled rice rate, head rice rate, chalkiness size, chalkiness grain rate, chalkiness degree, amylose content and protein content, improving rice processing and appearance qualities. For the Zn nutrition in rice grain, ZnO NPs application significantly increased the Zn content of edible polished rice and promoted the relocation of Zn from the aleurone layer. This study effectively demonstrated that ZnO NPs could be a potential high-performed fertiliser for enhancing rice yield and quality.

In this study, a redox precipitation method was used to load manganese dioxide (MnO₂) nanoparticles on biochar (BC) (BC@MnO₂) pyrolyzed from the invasive water hyacinth, and the adsorption of Cd(II),Cu(II), Zn(II), and Pb(II) was investigated. Several techniques were used to characterize the adsorbents. The results revealed that the BC surface was covered by many intertwined thin amorphous MnO₂ nanosheets, which significantly increased its specific surface area and pore volume. The adsorption of heavy metal ions by BC was negligible, whereas the MnO₂-containing adsorbents exhibited a high capacity for adsorbing heavy metal ions. However, the MnO₂-normalized adsorption amount decreased with increasing MnO₂ load and was largely unchanged at MnO₂ loads of 26.6% to 30.2%. The capacity for adsorbing heavy metal ions of BC@MnO₂ was pH-dependent, but the adsorption affinity was unaffected by coexisting ions. Column tests revealed that BC@MnO₂ with a load of 26.6% had a high capacity for removing heavy metal ions from simulated and real electroplating wastewater. Therefore, BC@MnO₂ with a load of 26.6% shows promise as a regenerable adsorbent for removing heavy metal ions from water/wastewater. This study could lay an essential foundation to develop a win-win strategy for heavy metal ions removal from wastewater using biochar derived from water hyacinth.