This study aims to investigate the effects of foliar nitrogen fertilizer (FNF) application at different times within the same period after mechanical harvesting of the main crop on the physiological characteristics, yield, and quality of ratoon rice, providing a scientific basis for increasing yield and improving quality of ratoon rice.

After the mechanical harvesting of the main crop, a field split-plot two-factor experiment was conducted in high-fertility (HF) and low-fertility (LF) fields. The main plots were assigned to rolling and non-rolling conditions, while the subplots were assigned to different FNF application times: spraying clean water on the day of harvesting (CK), and spraying FNF at 1 day (D1), 3 days (D3), and 7 days (D7) after harvesting. The physiological characteristics, yield, and quality of ratoon rice were measured to elucidate the effects of foliar nitrogen application timing on yield and quality.

The results showed that FNF significantly increased the SPAD value, dry matter weight, leaf area index, and effective panicle number of ratoon rice. Under both HF and LF conditions, FNF increased yield by 25.6%-82.8% by improving the effective panicle number. In the non-rolling area, no significant differences were observed among different FNF application timings, but all treatments significantly increased effective panicle number by 16.7%-30.6% and yield by 25.6%-36.7% compared to CK. In the rolling area, the yield enhancement effect gradually decreased with delayed FNF application. Under the D1 treatment, the effective panicle number significantly increased by 61.5% and 62.5%, and yield significantly increased by 74.9% and 82.8% under the two fertility conditions, respectively. FNF primarily improved the quality of ratoon rice by increasing the head rice rate and reducing the chalkiness rate. Compared to CK, in the non-rolling area, FNF significantly increased the head rice rate by 9.5%-17.8% and significantly reduced the chalkiness rate by 8.1%-15.3%; in the rolling area, FNF significantly increased the head rice rate by 15.0%-17.9% and significantly reduced the chalkiness rate by 9.2%-15.7%.

Foliar nitrogen fertilizer application after mechanical harvesting of the main crop effectively increases the yield and quality of ratoon rice. In rolling areas, the application timing significantly affects outcomes, with the best results achieved when spraying on the day of harvesting. In non-rolling areas, the application timing has no significant effect, and FNF can be applied within 7 days after harvesting.

To determine the effects of efficient, reduced-input pesticide and nitrogen (N) fertilizer application via unmanned aerial vehicles (UAVs) on the yield formation and energy efficiency of machine-transplanted rice. This study proposes an optimal model for adapting reduced N fertilizer and pesticide inputs to UAV operational efficiency, providing a theoretical foundation and practical basis for integrated UAV fertilizer and pesticide application systems.

A randomized block design was used with two drone flight speeds and four fertilizer-pesticide reduction treatments. Two drone speeds were set: 5.0 m/s (F₁) and 5.5 m/s (F₂). Four treatments with proportionally reduced N fertilizer and pesticide application were established: conventional application rate (N₁), 10% reduction (N₂), 20% reduction (N₃), and 30% reduction (N₄). Manual conventional application (CK₁) and no application (CK₂) served as controls. The study examined the effects of UAV flight speed and combined reduction treatments on machine-transplanted rice yield, plant population quality, and energy efficiency, while exploring the relationship between yield formation and energy efficiency under the UAV-based integrated fertilizer and pesticide application model.

Compared with the CK₁ treatment, the F₁N₁, F₂N₁, F₁N₂, and F₂N₂ treatments increased yields by 1.22%-1.96%, with no significant yield differences among treatments and disease control efficacy exceeding 84% in all cases. Notably, under 10% reduced fertilizer and pesticide application, treatments F₁N₂ and F₂N₂ exhibited increases of 1.73%-13.24% in both dry matter transport volume and rate, as well as N transport volume and rate. N partial factor productivity, N uptake efficiency, and N harvest index increased by 12.48%-12.89%, 17.84%-18.75%, and 1.86%-2.30%, respectively. Energy output, net energy and energy utilisation efficiency increased by 0.54%-0.66%, 0.98%-1.11%, and 5.47%-5.52%, respectively. Under identical fertilizer-pesticide regimes, a 10% increase in drone flight speed raised electricity consumption by 5.19%-10.11%. However, reduced labor hours offset electricity costs, yielding the highest net profit of 8,848.94 yuan/hm² under the F₂N₂ treatment. This demonstrates that a 10% increase in UAV speed combined with a 10% reduction in N fertilizer and pesticide application (F₂N₂ treatment) enhances operational efficiency and reduces production costs (labor) while maintaining net profit. This achieves cost savings and efficiency gains, representing the optimal production model for N fertilizer and pesticide reduction adapted to UAV operational efficiency in this trial.

The 10% drone speed increase coupled with 10% integrated N fertiliser and pesticide reduction drives synergistic optimization of yield, ecology, and energy efficiency in machine-transplanted rice through an optimised compensation mechanism. This achieves unified synergies of fertilizer and pesticide savings alongside high yields and efficiency, providing theoretical and technical support for fully mechanised green rice production.

To address the problem in single-planetary-wheelset transplanter mechanisms where the seedling picking and placing motions cannot be simultaneously optimized—thereby degrading transplanting quality—we propose a segmented variable gear-ratio wheelset mechanism whose rotation direction is opposite to that of conventional transplanting mechanisms and whose input and output periods are unequal.

First, we derived the continuous meshing angular condition equation for a segmented incomplete-gear set and solved for the motion parameters required for the segmented incomplete gear set to achieve continuous meshing. Next, by combining the non-uniform transmission ratio of an oval (non-circular) gear with the cubic high-amplitude fluctuation transmission ratio of the segmented incomplete gear, we obtained the multi-step unequal-amplitude transmission ratios required for the ring-loop (ankle-shaped) seedling-transplanting trajectory. We then established a kinematic model of a non-circular gear planetary wheelset transplanting mechanism that includes incomplete gear sets and developed a MATLAB-based auxiliary design program for the transplanter. At the same time, in accordance with rice seedling transplanting agronomic requirements and using a human-machine interactive selection process, we selected a set of mechanism parameters that realize a ring-loop transplanting trajectory capable of large pick displacement with slow picking (pick loop 47 mm) and a large planting angle (planting angle 80.6°).

Finally, we compared simulation results with theoretical calculations. The results show that the parameters of the incomplete gear set meet the requirements, and that the mechanism's motion trajectory and posture are in substantial agreement with theory.

Prototype tests measured a picking angle of 20.95° and a planting angle of 80.3°, validating the feasibility of the combined-variable transmission-ratio transplanting mechanism design.

To address the issues of poor seedling establishment and uneven population growth in direct-?seeded rice in southern China, caused by rice seeds are sown on the soil surface after mechanized direct seeding and are subsequently affected by climatic and ecological conditions.

Based on the principle of simultaneous coverage of rice seeds with powdered organic materials, theoretical analysis of a cam-plate metering and application device was conducted. The key parameters of the cam, discharge rotor, material push plate, and discharge apparatus were determined, and a powdered organic material discharge apparatus was designed. Bench tests were carried out. A prototype rice direct seeder with simultaneous powdered organic material coverage was fabricated, and its field performance was validated through field experiments.

The results showed that for the powdered organic materials [organic fertilizer, seedling nursery substrate, nutrient soil A, and nutrient soil B (a 2:1 mixture of nutrient soil A and organic fertilizer)], the coefficient of variation for application rate was below 7.80% at rotational speeds of 33-118 r/min, indicating good application stability. Due to the characteristics of the materials, the coverage thickness gradually decreased with increasing rotational speed, but remained stable. When applying the seedling nursery substrate, the coefficient of variation for coverage thickness fluctuated within a relatively large range of 9.41%-18.67%. When applying organic fertilizer, nutrient soil A, and nutrient soil B, the coefficient of variation for coverage thickness was below 15% in all cases, meeting the agronomic requirements for simultaneous coverage of rice seeds with powdered organic materials. Regression equations for coverage thickness were established, all with fitting degrees exceeding 0.95. Field experiment results showed that for the rice varieties Zhongjiazao 17 and Wufengyou 286, the average emergence rates under the coverage treatment increased by 19.59% and 22.65%, respectively, compared with the non-covered treatment.

This apparatus improves the mechanized level of rice cultivation and provide a reference for the design of complete rice direct seeding machines with simultaneous powdered organic material coverage.

Weakened seed dormancy in rice leads to pre-harvest sprouting (PHS), which severely impacts grain yield and quality, making it crucial to investigate the genetic regulatory mechanisms underlying rice seed dormancy.

We generated loss-of-function mutants of the AP2/ERF transcription factor OsERF34 in the Zhonghua 11 (ZH11) background using CRISPR/Cas9 technology.

The oserf34 mutants exhibited severe pre-harvest sprouting and significantly reduced seed dormancy. Transcriptome analysis revealed that differentially expressed genes (DEGs) between oserf34 and the wild type were significantly enriched in plant hormone signal transduction, ROS metabolism, and glycolytic pathways, suggesting that OsERF34 may maintain seed dormancy by regulating hormone biosynthesis/metabolism, redox homeostasis, and carbohydrate metabolism. Further investigation demonstrated that the oserf34 mutant seeds showed substantially increased levels of auxin (IAA), gibberellins (GA19/GA20), and salicylic acid (SA), along with decreased proline content and elevated hydrogen peroxide (H₂O₂) and superoxide anion level. Meanwhile, the activities of antioxidant enzymes (SOD, POD, CAT) were upregulated. Additionally, the mutant endosperm exhibited significantly elevated soluble sugar content and α-amylase activity, providing an energy foundation for dormancy release. This study demonstrates that OsERF34 positively regulates rice seed dormancy through its involvement in hormone biosynthesis/metabolism, redox homeostasis regulation, and carbohydrate metabolism.

These findings provide novel theoretical insights and genetic resources for deciphering the molecular mechanisms of seed dormancy and germination, as well as for developing PHS-resistant rice varieties.

Rice glume development directly affects both grain yield and quality. Identifying genes that control glume development and characterizing their functions can provide valuable genetic resources for breeding.

The split glume 5 (sg5) mutant was isolated from a mutant library generated by ethyl methanesulfonate (EMS) mutagenesis of the rice variety Xudao 3 (XU3). Phenotypic investigation and analysis were performed on both the wild type and the sg5 mutant. SG5 was identified using a combination of map-based cloning and bulked segregant analysis sequencing (BSA-seq). The temporal and spatial expression patterns of SG5 were examined by qRT PCR and GUS staining. Subcellular localization of SG5 was observed in rice protoplasts. An evolutionary tree was constructed to analyze the natural selection of SG5.

The mutant exhibited normal glume development before flowering, but the glumes remained split until maturity. Compared with the wild type, the mutant showed earlier heading, longer panicles, reduced grain length and width, and a significantly lower seed-setting rate, while plant height and effective panicle number remained unchanged. Microscopic observation indicated that the split glume phenotype was caused by persistent swelling of the lodicules. SG5 was mapped to a 3.72 Mb physical interval between InDel5-11 and InDel5-13 on chromosome 5. In the sg5 mutant, a G-to-A mutation at the junction of intron 3 and exon 4 of LOC_Os05g50890 led to alternative splicing and premature protein termination. Knockout experiments confirmed that SG5 is the target gene. SG5 is constitutively expressed, with higher transcript levels in roots, stems, and leaves. The SG5 protein localizes to both the cytoplasm and nucleus. Evolutionary analysis revealed that SG5 has undergone differentiation between indica and japonica subspecies during evolution.

This study identifies a novel allele of OsJar1 and reveals that SG5 has diverged between indica and japonica under natural selection. These findings provide new clues for further dissection of the molecular regulatory network controlling glume development and offer valuable genetic resources for precision breeding in rice.