Rice Genomics and Genetics 2025, Vol.16 http://cropscipublisher.com/index.php/rgg © 2025 CropSci Publisher, registered at the publishing platform that is operated by Sophia Publishing Group, foundedin British Columbia of Canada. All Rights Reserved.
Rice Genomics and Genetics 2025, Vol.16 http://cropscipublisher.com/index.php/rgg © 2025 CropSci Publisher, registered at the publishing platform that is operated by Sophia Publishing Group, foundedin British Columbia of Canada. All Rights Reserved. CropSci Publisher is an international Open Access publishing specializing in crop genome, trait-controlling, crop gene expression and regulation at the publishing platform that is operated by Sophia Publishing Group (SPG), founded in British Columbia of Canada. Publisher CropSci Publisher Edited by Editorial Team of Rice Genomics and Genetics Email: edit@rgg.cropscipublisher.com Website: http://cropscipublisher.com/index.php/rgg Address: 11388 Stevenston Hwy, PO Box 96016, Richmond, V7A 5J5, British Columbia Canada Rice Genomics and Genetics (ISSN 1925-2021) is an open access, peer reviewed journal published online by CropSciPublisher. The journal publishes original research papers of Rice Genomics and Genetics should be innovative research work in field of rice research, particular in the areas of rice functional genomics, transgene, genome sequencing analysis, molecular genetics, proteomics, genetic diversity, dominance relationships, heterosis, genetic characteristics, genetic modification, genetic rule analysis, genotype-phenotype relationships, stress physiology characteristics, QTL analysis and advanced rice breeding technologies. All the articles published in Rice Genomics and Genetics are Open Access, and are distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. CropSciPublisher uses CrossCheck service to identify academic plagiarism through the world’s leading plagiarism prevention tool, iParadigms, and to protect the original authors’ copyrights.
Rice Genomics and Genetics (online), 2025, Vol. 16, No. 2 ISSN 1925-2021 http://cropscipublisher.com/index.php/rgg © 2025 CropSci Publisher, an online publishing platform of Sophia Publishing Group. All Rights Reserved. Sophia Publishing Group (SPG), founded in British Columbia of Canada, is a multilingual publisher Latest Content Improving Rice Yield under Direct Seeding through Synergistic Water and Fertilizer Management Dengjun Liu Rice Genomics and Genetics, 2025, Vol.16, No.2, 61-70 Optimizing Planting Density to Enhance Rice Productivity Xiaoying Zhu Rice Genomics and Genetics, 2025, Vol.16, No.2, 71-85 Molecular Functions and Regulatory Mechanisms of the Temperature-Sensitive Male Sterility Gene OsTms6 inRice Weijie Sun, Chengxi Wang, Jiawei Li Rice Genomics and Genetics, 2025, Vol.16, No.2, 86-95 Phylogenetic Evolution of Rice: A Comprehensive Review of Domestication Events and Wild Progenitors Zhongxian Li, Zufan Chen, Qifu Zhang Rice Genomics and Genetics, 2025, Vol.16, No.2, 96-105 Functional Genomics of Rice: Recent Discoveries and Future Prospects Yanfu Wang, Danyan Ding Rice Genomics and Genetics, 2025, Vol.16, No.2, 106-115
Rice Genomics and Genetics 2025, Vol.16, No.2, 61-70 http://cropscipublisher.com/index.php/rgg 61 Research Insight Open Access Improving Rice Yield under Direct Seeding through Synergistic Water and Fertilizer Management Dengjun Liu 1,2 1 Youhe Youmi Agricultural Development (Jiaxing) Co., Ltd., Pinghu, 314200, Zhejiang, China 2 Zhejiang Agronomist College, Hangzhou, 310021, Zhejiang, China Corresponding email: 806972515@qq.com Rice Genomics and Genetics, 2025, Vol.16, No.2 doi: 10.5376/rgg.2025.16.0006 Received: 12 Jan., 2025 Accepted: 26 Feb., 2025 Published: 08 Mar., 2025 Copyright © 2025 Liu, This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Preferred citation for this article: Liu D.J., 2025, Improving rice yield under direct seeding through synergistic water and fertilizer management, Rice Genomics and Genetics, 16(2): 61-70 (doi: 10.5376/rgg.2025.16.0006) Abstract This study focuses on the role of integrated water and fertilizer management in improving yield, quality, and resource use efficiency in direct-seeded rice systems. The findings reveal that comprehensive practices combining Alternate Wetting and Drying (AWD) with Site-Specific Nutrient Management (SSNM), controlled-release fertilizers, and precise nitrogen management significantly enhance yield components, water productivity, and nitrogen use efficiency in direct-seeded rice. Simultaneously, these strategies reduce greenhouse gas emissions and nutrient losses, mitigating environmental impacts. Case studies further validate the practical effectiveness of these approaches, demonstrating the feasibility of achieving high yields and sustainability in direct-seeded rice systems. This study underscores the critical importance of water and fertilizer synergy in enhancing the productivity and sustainability of direct-seeded rice, aiming to provide actionable solutions for addressing global food security challenges under resource constraints and offering directions for sustainable rice production. Keywords Direct-seeded rice (DSR); Water and fertilizer synergy; Precision nutrient management; Alternate wetting and drying (AWD); Sustainable rice production 1 Introduction Direct-seeded rice (DSR) systems have emerged as a promising alternative to traditional transplanted rice due to their reduced labor and water requirements, which are critical in the face of increasing resource scarcity and labor shortages (Xu et al., 2019; Bhandari et al., 2020; Rathika et al., 2020). However, DSR systems often face challenges such as lower yields compared to transplanted rice, primarily due to issues like poor crop establishment, high weed infestation, and suboptimal nutrient management (Sandhu et al., 2021). Therefore, improving rice yield under DSR systems is crucial for ensuring food security and sustainability in rice production, especially in regions where water and labor are limiting factors (Xu et al., 2019; Bhandari et al., 2020). Effective water and fertilizer management are pivotal in enhancing the productivity of DSR systems. Studies have shown that precision nitrogen management and optimized irrigation strategies can significantly improve grain yield, water productivity, and nutrient use efficiency in DSR (Kumar et al., 2019; Pratap et al., 2022). For instance, the integration of soil matric potential-based irrigation strategies with precise nitrogen application has been demonstrated to maximize yield while minimizing water input (Kumar et al., 2019). Additionally, the use of soil test-based fertilizer applications has been found to enhance nutrient uptake and yield, further highlighting the importance of synergistic management practices (Singh et al., 2021). These strategies not only improve yield but also contribute to better resource use efficiency and environmental sustainability (Kumar et al., 2019; Singh et al., 2021; Pratap et al., 2022). This study investigates the synergistic effects of water and fertilizer management on improving rice yield under direct-seeded conditions. By exploring various management strategies, this study aims to identify optimal practices that enhance yield, resource use efficiency, and economic returns in DSR systems, and hopes that the findings are expected to provide valuable insights into developing sustainable and efficient rice production systems that can address the challenges posed by resource constraints and environmental concerns.
Rice Genomics and Genetics 2025, Vol.16, No.2, 61-70 http://cropscipublisher.com/index.php/rgg 62 2 Direct-Seeding Systems in Rice 2.1 Characteristics of direct-seeding systems Direct-seeding systems in rice cultivation have gained popularity due to their labor-saving benefits and adaptability to mechanization. This method involves sowing seeds directly into the field, bypassing the traditional transplanting stage. Direct seeding can be implemented in both wet and dry conditions, offering flexibility in water management. The system is known for its potential to reduce production costs and improve resource use efficiency, such as water and nitrogen, compared to traditional methods (Liu et al., 2014; Santiago‐Arenas et al., 2021; Guo et al., 2022; Wu et al., 2023). According to our analysis of the 2024 rice trial data, compared to seedling transplanting (mechanized rice transplanting), direct seeding (drone broadcast seeding) resulted in a 33.3% increase in field mechanization costs and a 20% increase in seed costs. However, labor costs decreased by 78.8%, leading to an overall cost reduction of 29.5%. 2.2 Agronomic challenges in direct-seeding systems Despite its advantages, direct-seeding systems face several agronomic challenges. One major issue is the management of nitrogen fertilizer, which is crucial for optimizing yield and nitrogen use efficiency (NUE). Inappropriate nitrogen management can lead to reduced seedling emergence and lower yields (Ma et al., 2023). Additionally, direct-seeded rice is more susceptible to weed competition and requires precise water management to prevent water stress or excessive water use (Santiago‐Arenas et al., 2021; Fu et al., 2023). The system also demands careful attention to soil health and structure, as these factors significantly influence root development and nutrient uptake (Guo et al., 2022). 2.3 Role of water and fertilizer in yield optimization Water and fertilizer management play a pivotal role in optimizing yields in direct-seeding systems. Synergistic management of these inputs can enhance rice yield, quality, and resource use efficiency. For instance, controlled-release fertilizers combined with appropriate irrigation strategies can reduce nitrogen losses and improve NUE, leading to higher yields (Wu et al., 2023; Zhu et al., 2024b). Studies have shown that optimizing the timing and method of nitrogen application, such as transferring a portion of nitrogen from basal to tillering stages, can significantly increase yield and improve plant development (Li et al., 2024; Zhu et al., 2024a). Moreover, innovative irrigation methods, like alternate wetting and drying, have been found to save water while maintaining comparable yields to continuous flooding systems (Tao et al., 2015; Santiago‐Arenas et al., 2021). These strategies highlight the importance of integrated water and fertilizer management in achieving sustainable and high-yielding direct-seeded rice systems. 3 Synergistic Water and Fertilizer Management 3.1 Water management strategies Water management plays a pivotal role in rice cultivation, influencing both yield and resource efficiency. Several strategies have been identified to optimize water use. Alternate wetting and drying (AWD) has been shown to save 40%~44% more water compared to continuous flooding, while maintaining similar grain yields. AWD also enhances water productivity by 68% (Santiago‐Arenas et al., 2021). Implementing a 30% water-saving irrigation strategy can significantly improve dry matter quality, yield, and nutrient absorption in dry direct-seeded rice. This approach enhances rice processing, appearance, and nutritional quality (Lu and Li, 2023). Wet-shallow irrigation reduces irrigation water use by 35.2% and increases irrigation water productivity by 42.0%~42.8%, thereby improving overall water productivity (Zhu et al., 2024a). 3.2 Fertilizer application techniques Optimizing fertilizer application is essential for improving rice yield and nitrogen use efficiency (NUE). Combining controlled-release fertilizers with urea reduces nitrogen losses and enhances NUE and yield in wet direct-seeded rice (Wu et al., 2023). Transferring 20% of total nitrogen from basal to tillering stages significantly increases yield and improves nitrogen use efficiency in direct-seeded ratoon rice systems (Li et al., 2024). The use of bioorganic fertilizers, such as Jishiwang combined with conventional NPK, enhances soil fungal community diversity and increases rice yield (Guo et al., 2022).
Rice Genomics and Genetics 2025, Vol.16, No.2, 61-70 http://cropscipublisher.com/index.php/rgg 63 3.3 Synergistic approaches Integrating water and fertilizer management strategies can lead to synergistic effects, enhancing rice yield and quality. The combination of wet irrigation and optimized nitrogen application (e.g., 225 kg/ha) significantly improves photosynthetic efficiency, non-structural carbohydrate accumulation, and lodging resistance, leading to higher yields and better rice quality (Figure 1) (Zhu et al., 2024b). Simplified and nitrogen-reduced practices, which involve reduced nitrogen fertilizer and labor input, have been shown to increase grain yield and NUE by enhancing sink capacity, productive tillers, and biomass accumulation (Fu et al., 2023). Utilizing controlled-release nitrogen fertilizers in a one-time application can balance yield, quality, and economic benefits, reducing fertilization frequency while maintaining high yield and quality (Cheng et al., 2023). Figure 1 Synergistic regulation of yield, quality, and lodging resistance by water and fertilizer management (Adopted from Zhu et al., 2024b) 4 Physiological Responses of Rice to Water and Nutrient Synergy 4.1 Growth dynamics and biomass accumulation The synergy between water and nutrient management significantly influences the growth dynamics and biomass accumulation in rice. Optimized water and fertilizer management, such as the W1F3 treatment, enhances photosynthetic efficiency and non-structural carbohydrate (NSC) accumulation, which are crucial for robust growth and high yield (Zhu et al., 2024b). Additionally, treatments like W1N2 have been shown to increase grain biomass accumulation by improving root oxidation activity and hormone balance, which supports effective panicle number and seed-setting performance (Zhao et al., 2023). The application of controlled-release fertilizers also extends the duration of rapid nitrogen growth, enhancing nitrogen accumulation and transport, which contributes to increased biomass and yield (Wu et al., 2023).
Rice Genomics and Genetics 2025, Vol.16, No.2, 61-70 http://cropscipublisher.com/index.php/rgg 64 4.2 Stress tolerance Water and nutrient synergy plays a vital role in enhancing rice's stress tolerance. The integration of water-saving irrigation techniques with nutrient management, such as the 30% water-saving irrigation combined with conditioners, improves rice's resilience during critical growth stages like tillering and grain filling (Lu and Li, 2023). This approach not only supports better growth under water-limited conditions but also enhances nutrient absorption, contributing to improved stress tolerance. Moreover, the use of optimized nitrogen management strategies, such as the N4 treatment, reduces ammonia volatilization and supports delayed senescence, which helps maintain higher leaf SPAD values and canopy photoassimilation, thereby enhancing stress tolerance (Ma et al., 2023). 4.3 Yield components The synergistic management of water and nutrients significantly impacts the yield components of rice. For instance, the W1F3 treatment has been identified as optimal for increasing nitrogen uptake and improving the harvest index, leading to higher yields (Zhu et al., 2024a). Similarly, the use of controlled-release fertilizers combined with urea (CRBF+U) has been shown to improve the grain number per panicle, seed-setting rate, and actual yield by enhancing nitrogen use efficiency and reducing nitrogen losses (Wu et al., 2023). Additionally, integrated nutrient management strategies, such as combining organic and inorganic sources with biofertilizers, have been found to enhance yield attributes like panicle length and grain weight, ultimately boosting productivity and profitability (Table 1) (Kumar et al., 2023). 5 Environmental Implications of Water and Fertilizer Management 5.1 Water use efficiency and conservation Water management strategies such as alternate wetting and drying (AWD) and optimized irrigation schedules have been shown to significantly improve water use efficiency in rice cultivation. For instance, AWD can save 40%~44% of water compared to continuous flooding, while maintaining similar grain yields (Santiago‐Arenas et al., 2021). Additionally, the use of water-saving irrigation methods like “thin, shallow, wet, dry irrigation” can reduce irrigation water by 35.2% and increase water productivity by 42.0%~42.8% (Zhu et al., 2024a). These strategies not only conserve water but also enhance the sustainability of rice production systems. Through comparative experiments, we found that before rice seedlings reached a height of 5 cm, drone direct seeding required two fewer irrigation cycles and reduced water usage by 50% compared to mechanized transplanting, while the rice yield remained nearly the same. 5.2 Nutrient use efficiency and pollution reduction Optimizing nitrogen (N) management is crucial for improving nutrient use efficiency and reducing environmental pollution. Precision nutrient management techniques, such as the use of Nutrient Expert® and SPAD meter-based N management, have been shown to save up to 27.1% of nitrogen while increasing grain yields and water productivity (Pratap et al., 2022). Moreover, reducing nitrogen application rates from 120 to 60 kg/ha can achieve desirable grain yields and water productivity, significantly lowering fertilizer input costs and environmental impact (Santiago‐Arenas et al., 2021). These practices help in minimizing nitrogen losses and reducing greenhouse gas emissions, such as nitrous oxide (N2O) (Sadhukhan et al., 2023). 5.3 Ecosystem services Water and fertilizer management also play a role in enhancing ecosystem services. The integration of organic fertilizers with conventional NPK fertilizers can improve soil health by enhancing the soil fungal community, which in turn supports higher rice yields (Guo et al., 2022). Additionally, improved water management practices can reduce methane (CH4) emissions by 30%~34% and nitrous oxide emissions by 64%~66%, contributing to a lower greenhouse gas footprint (Islam et al., 2020). These practices not only support sustainable rice production but also contribute to broader environmental benefits by maintaining ecosystem balance and reducing pollution.
Rice Genomics and Genetics 2025, Vol.16, No.2, 61-70 http://cropscipublisher.com/index.php/rgg 65 Table 1 Effect of integrated nutrient management on yield attributes of direct seeded rice under Rainfed conditions (Adopted from Kumar et al., 2023) Treatment Number of tillers Panicle length (cm) Panicle Weight (g) Number of filled grains Panicle-1 Total Number of grain spanicle -1 Grain yield panicle-1 (g) 1000-grain weight (g) Productive tillers (m-2) Unproductiv e tillers (m-2) T1 Control 274.33 54.00 19.13 2.40 45.00 54.66 0.92 20.63 T2 100% recommended dose of NPK through fertilizer (100 kg N+40 kg P2O5+ 40 kg K2O/ha) 321.66 49.00 22.33 3.41 73.33 80.66 1.89 25.84 T3 100% RDN through compost 309.33 50.00 20.96 3.01 68.66 76.66 1.74 25.48 T4 50% RDN through fertilizer + 50% RDN through compost 317.66 49.33 21.10 3.23 69.66 77.33 1.80 25.91 T5 50% RDN through fertilizer + 25% RDN through compost 295.00 51.66 18.03 2.71 61.00 70.00 1.51 24.76 T6 25% RDN through fertilizer + 50% RDN through compost 287.00 52.00 17.9 2.63 60.33 69.66 1.48 24.67 T7 50% RDN through fertilizer + 25% RDN through compost + seed treated with Azotobacter @ 10 g/kg seed 304.00 50.33 19.53 2.96 66.66 74.66 1.69 25.40 T8 25% RDN through fertilizer + 50% RDN through compost + seed treated with Azotobacter @ 10 g/kg seed 298.33 51.33 19.43 2.92 65.66 73.33 1.66 25.33 T9 50% RDN through fertilizer + 50% RDN through compost + seed treated with Azotobacter @ 10 g/kg seed 340.66 46.66 23.57 3.76 75.33 82.33 2.01 26.69 SEm± - 4.22 1.24 1.03 0.20 1.22 1.22 0.10 0.70 CD(5%) - 12.67 3.74 3.09 0.61 3.66 3.67 0.30 2.33
Rice Genomics and Genetics 2025, Vol.16, No.2, 61-70 http://cropscipublisher.com/index.php/rgg 66 6 Case Study 6.1 Case study 1: AWD and SSNM integration in Southeast Asia The integration of Alternate Wetting and Drying (AWD) with Site-Specific Nutrient Management (SSNM) has shown promising results in Southeast Asia. This approach has been effective in reducing water inputs by 13.4% to 27.5% and surface runoff by 30.2% to 36.7% compared to conventional practices. Additionally, the combination of AWD and SSNM significantly reduced nitrogen (N) and phosphorus (P) losses via surface runoff by 39.4% to 47.6% and 46.1% to 48.3%, respectively, while maintaining high rice yields. This synergy not only enhances water and nutrient use efficiency but also mitigates environmental impacts, making it a sustainable practice for rice cultivation in the region (Liang et al., 2013; Liu et al., 2013). 6.2 Case study 2: precision nutrient management in India In India, precision nutrient management has been implemented in zero-till direct-seeded rice systems, leading to improved productivity and environmental benefits. The use of soil-test-based NPK (STB-NPK) and Nutrient Expert® (NE-NPK) applications resulted in a 12% higher grain yield over the recommended dose of fertilizers. Moreover, NE-NPK increased agronomic efficiency of nitrogen (AEN) by 7% and phosphorus (AEP) by 35% compared to STB-NPK. This approach also significantly reduced nitrous oxide (N2O) emissions by 49%, highlighting its potential to enhance nutrient use efficiency and reduce greenhouse gas emissions in rice production (Khurana et al., 2007; Sadhukhan et al., 2023). 6.3 Case Study 3: mechanized precision dry direct seeding technology for rice in China In recent years, mechanized precision dry direct seeding technology has been tested, demonstrated, and promoted in China, particularly in areas where irrigation is inconvenient or water retention is poor. This technology eliminates the need for seedling cultivation, field soaking, and transplanting. Instead, it involves directly sowing an accurate amount of seeds into the field using machinery. As a simplified rice cultivation method, it reduces labor and time requirements, conserves water, lowers costs, and is well-suited for large-scale mechanized operations, ultimately enhancing cost efficiency, quality, and productivity in rice production (Wang et al., 2020). According to our 2024 trial results, the total time required from seed preparation to field seeding (or transplanting) with precision dry direct seeding was only 2.5 days, which was 2.5 days shorter than mechanized direct seeding and 18 days shorter than mechanized transplanting, significantly reducing the planting duration. From a cost-saving perspective, precision dry direct seeding reduced costs by 56% compared to mechanized direct seeding and 101.6% compared to mechanized transplanting. Regarding seedling quality and weed incidence, the seedling quality of precision dry direct seeding was comparable to that of other methods. However, mechanized transplanting had slightly lower weed incidence and a slightly higher seedling establishment rate (Figure 2). At harvest, the thousand-grain weight for precision dry direct seeding was 24.6 g, which was higher than 21.6 g for mechanized direct seeding and 24.1 g for mechanized transplanting. In terms of final rice yield, precision dry direct seeding outperformed mechanized direct seeding by 5.10% and mechanized transplanting by 2.98%, demonstrating its potential as an efficient and cost-effective rice cultivation method. Figure 2 Comparison of seedling quality in the field across three rice sowing methods Image caption: a: Precision dry direct seeding; b: Mechanized direct seeding; c: Mechanized transplanting
Rice Genomics and Genetics 2025, Vol.16, No.2, 61-70 http://cropscipublisher.com/index.php/rgg 67 6.4 Lessons learned from case studies The case studies demonstrate that integrating advanced water management techniques like AWD with precision nutrient management strategies such as SSNM can significantly improve rice yield and resource-use efficiency. These practices not only enhance productivity but also contribute to environmental sustainability by reducing water usage and nutrient losses. The success of these strategies in different regions underscores the importance of tailoring agricultural practices to local conditions to achieve optimal results. The lessons learned emphasize the need for continued innovation and adaptation in rice cultivation to address the challenges of water scarcity and environmental degradation while ensuring food security (Khurana et al., 2007; Liang et al., 2013; Liu et al., 2013; Sadhukhan et al., 2023). 7 Technological Innovations in Water and Fertilizer Management 7.1 Smart irrigation systems Smart irrigation systems, such as those utilizing sensors and the Internet of Things (IoT), have been identified as effective methods to enhance water use efficiency in rice farming. These systems allow for precise control of water application, reducing wastage and improving crop yield. However, the high cost of these technologies can be a barrier for small-scale farmers (Figure 3) (Mallareddy et al., 2023). Alternate wetting and drying (AWD) is another smart irrigation technique that has been shown to save water and maintain yields, while also reducing greenhouse gas emissions (Islam et al., 2020; Huang, 2024). Figure 3 A smart irrigation device installed in the field (Adopted from Mallareddy et al., 2023) 7.2 Precision agriculture tools Precision agriculture tools, including precision nutrient management systems, have been shown to significantly improve the productivity and efficiency of direct-seeded rice. For instance, the use of Nutrient Expert® and SPAD meter-based nitrogen management has been demonstrated to enhance grain yields and water productivity while reducing nitrogen use by approximately 27.1% (Pratap et al., 2022). These tools help in optimizing the application of fertilizers, thereby increasing nutrient use efficiency and reducing environmental impact (Sadhukhan et al., 2023).
Rice Genomics and Genetics 2025, Vol.16, No.2, 61-70 http://cropscipublisher.com/index.php/rgg 68 7.3 Digital decision support systems Digital decision support systems (DSS) are increasingly being used to optimize water and fertilizer management in rice cultivation. These systems integrate data from various sources to provide real-time recommendations for irrigation and fertilization, thus enhancing resource use efficiency. For example, DSS can help in determining the optimal timing and amount of irrigation and fertilizer application, which can lead to improved yields and reduced input costs (Santiago‐Arenas et al., 2021; Zhu et al., 2024a). By leveraging data analytics, these systems can also predict crop performance under different management scenarios, aiding in better decision-making (Zhu et al., 2024b). 8 Challenges and Future Directions The adoption of direct seeding in rice production faces several barriers despite its potential benefits in water and labor savings. One significant challenge is the increased fertilizer use associated with direct seeding, which can deter farmers due to higher input costs and environmental concerns (Zhang and Hu, 2022). Additionally, the transition from traditional transplanting methods to direct seeding requires changes in farm management practices, which can be a barrier for farmers accustomed to conventional methods (Zhang et al., 2018). The need for precise water and nitrogen management to optimize yield and resource use efficiency further complicates adoption (Pratap et al., 2022). Enhancing the climate resilience of direct-seeded rice systems is crucial, given the increasing variability in weather patterns. Water management strategies such as alternate wetting and drying (AWD) have shown promise in reducing water use and greenhouse gas emissions, contributing to more sustainable rice production (Islam et al., 2020). However, these methods require careful implementation to maintain yield levels, which can be challenging under unpredictable climate conditions (Santiago‐Arenas et al., 2021). The integration of organic fertilizers has also been suggested to improve soil health and resilience, although this approach requires further research to optimize its effectiveness in different environmental contexts (Guo et al., 2022). Future research should focus on optimizing water and fertilizer management to enhance yield and resource use efficiency in direct-seeded rice systems. Studies have highlighted the potential of precision nitrogen management and controlled-release fertilizers to improve nitrogen use efficiency and reduce environmental impacts (Zhang et al., 2018; Fu et al., 2023). Additionally, exploring the synergistic effects of combined organic and inorganic fertilization on soil health and yield could provide insights into sustainable practices (Guo et al., 2022). Research should also prioritize developing climate-resilient rice varieties and management practices that can withstand extreme weather events while maintaining productivity (Zhu et al., 2024b). Acknowledgments The author expresses deep gratitude to Professor R. Cai from the Zhejiang Agronomist College for his thorough review of the manuscript and constructive suggestions. The author also extends thanks to the two anonymous peer reviewers for their valuable revision recommendations.The project was supported by Pinghu Agricultural Technology Extension Foundation in 2024 Conflict of Interest Disclosure The author affirms that this research was conducted without any commercial or financial relationships that could be construed as a potential conflict of interest. References Bhandari S., Khanal S., and Dhakal S., 2020, Adoption of direct seeded rice (DSR) over puddled-transplanted rice (TPR) for resource conservation and increasing wheat yield, Reviews in Food and Agriculture, 1: 59-66. https://doi.org/10.26480/rfna.02.2020.59.66 Cheng S., Xing Z., Tian C., Weng W., Hu Q., and Zhang H., 2023, Optimization of one-time fertilization scheme achieved the balance of yield, quality and economic benefits of direct-seeded rice, Plants, 12(10): 2047. https://doi.org/10.3390/plants12102047 Fu Y., Huang N., Zhong X., Mai G., Pan H., Xu H., Liu Y., Liang K., Pan J., Xiao J., Hu X., Hu R., Li M., and Ye Q., 2023, Improving grain yield and nitrogen use efficiency of direct-seeded rice with simplified and nitrogen-reduced practices under a double-cropping system in South China, Journal of the Science of Food and Agriculture, 103(12): 5727-5737. https://doi.org/10.1002/jsfa.12644
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Rice Genomics and Genetics 2025, Vol.16, No.2, 71-85 http://cropscipublisher.com/index.php/rgg 71 Feature Review Open Access Optimizing Planting Density to Enhance Rice Productivity Xiaoying Zhu1,2 1 Deqing Xinshi Changlin Family Farm, Deqing, 313201, Zhejiang, China 2 Zhejiang Agronomist College, Hangzhou, 310021, Zhejiang, China Corresponding email: 181833674@qq.com Rice Genomics and Genetics, 2025, Vol.16, No.2 doi: 10.5376/rgg.2025.16.0007 Received: 20 Jan., 2025 Accepted: 28 Feb., 2025 Published: 10 Mar., 2025 Copyright © 2025 Zhu, This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Preferred citation for this article: Zhu X.Y., 2025, Optimizing planting density to enhance rice productivity, Rice Genomics and Genetics, 16(2): 71-85 (doi: 10.5376/rgg.2025.16.0007) Abstract Improving rice yield is of great significance to food security. Under limited arable land conditions, improving yield per unit area by optimizing cultivation measures is a key strategy. Planting density is an important factor affecting rice population growth, yield formation and resource utilization efficiency. This study systematically analyzes the theoretical basis and mechanism of optimizing planting density to improve rice productivity, including the impact on plant growth and development, yield composition, rice quality and economic benefits, and discusses it in combination with practical cases in Nanchang, Jiangxi and Leshan, Sichuan. Studies have shown that a reasonable increase in planting density can increase the number of effective panicles and the number of panicles per unit area, thereby significantly increasing rice yield, but too high density will lead to intensified individual competition, a decrease in the number of panicles, a decrease in the fruiting rate, and an increase in the risk of lodging and disease, which will ultimately be counterproductive. The optimal density varies under different ecological regions and cultivation methods, and should be optimized according to local conditions such as variety characteristics, nitrogen fertilizer management and climatic conditions. The Nanchang Plain double-season rice area has achieved good results by appropriately reducing the sowing density to enhance individual lodging resistance, while the Leshan hilly area has achieved group yield increase through close planting combined with machine transplanting. In general, optimizing planting density requires balancing the relationship between group and individual, source of production and source of storage, to achieve high yield and high efficiency and stable yield and increase income. The comprehensive analysis of this article can provide a scientific basis for high-yield rice cultivation. Keywords Rice; Planting density; Group growth; Yield composition; Economic benefits; Regional practice 1 Introduction Rice is the staple food crop for nearly half of the world's population, and improving rice productivity is crucial to ensuring food security. Against the backdrop of limited arable land resources and intensified climate change challenges, how to achieve continuous improvement in rice yield per unit area by optimizing agronomic measures has become a research hotspot and a practical need (Guo et al., 2024). As an important parameter of rice cultivation, planting density (planting density) directly affects population structure and individual development, and plays a key role in the final yield formation. Traditional cultivation often relies on experience to determine density, but there are differences in the optimal density under different varieties and habitat conditions; too sparse planting leads to the failure to fully utilize the production potential of the population, while too dense planting causes individual competition and the risk of lodging and yield reduction. In recent years, with the development of super rice breeding and mechanized cultivation, the theory of achieving high yield through "moderate dense planting" has been proposed. For example, hybrid rice breeding experts in China pointed out that high-yield cultivation not only depends on the genetic potential of the variety, but also requires the coordination of reasonable basic seedlings and population structure (Jiang et al., 2025). Studies have shown that increasing the basic seedling density in combination with single-plant planting is expected to make full use of space resources, promote the construction of large rice populations, and achieve increased yields (Tian et al., 2022). At the same time, the emphasis on density optimization under different ecological conditions is different. For example, double-season rice areas often face the problems of high temperature and high humidity, and plants are prone to excessive growth and lodging. It is necessary to control the basic seedlings to improve the stable yield of the group, while dryland cultivation or direct seeding cultivation often requires increasing the sowing amount to
Rice Genomics and Genetics 2025, Vol.16, No.2, 71-85 http://cropscipublisher.com/index.php/rgg 72 ensure sufficient seedlings to suppress weeds and ensure yield. Therefore, it is necessary to systematically summarize the impact mechanism of planting density optimization on rice productivity and propose strategies adapted to local conditions in combination with regional practices. This study focuses on the optimization of rice planting density, expounds its theoretical basis, including the theory of population quality formation and the principle of source-sink balance, etc.; analyzes the influence of density on rice growth and development; explores the mechanism of density regulation on yield and composition elements, as well as the impact on rice quality and nitrogen utilization; evaluates the economic benefits of different density treatments; and combines typical practical cases in Nanchang and plain areas of Jiangxi Province and Leshan hilly areas of Sichuan Province to explore the application effects and inspirations of density optimization in different regions. Through literature review and case analysis, this study hopes to provide scientific basis and practical guidance for optimizing planting density to improve rice high yield and efficiency. 2 Physiological Mechanism and Ecological Adaptability of Planting Density Optimization 2.1 Coordination between plant population and individual growth Rice yield depends on the balanced optimization of group and individual performance, that is, building an ideal group structure to maximize light energy utilization and dry matter accumulation, while ensuring that individual plants have sufficient panicle and fruiting capacity. Planting density directly determines the basic seedling number and the development trend of the group, and is an important regulatory means that affects the three elements of rice yield composition: "number of panicles-number of grains per panicle-grain weight". The theoretical basis of density optimization can be understood from two aspects: group ecology and crop physiology: 2.2 Light interception and canopy ventilation On the one hand, planting density affects the light interception ability and canopy structure of the group. Under appropriate density, the group can cover the soil surface earlier, increase the leaf area index (LAI), and fully intercept light energy for photosynthesis. Studies have shown that increasing the basic seedling number within a certain range can increase the early LAI and photosynthetic potential of the group, but too high a density will lead to group closure, insufficient light for the lower leaves, and decreased photosynthetic efficiency (Zhang et al., 2021). The experiment of Xie et al. (2016) showed that high basic seedlings and single machine transplanting can form a large group leaf area in the early stage, which promotes the accumulation of total dry matter. However, after exceeding the optimal density, the photosynthetic productivity of the group decreases, and the yield decreases with the increase of density. Therefore, there is a concept of "optimal group leaf area", which makes the utilization of light energy and respiratory consumption of the group reach a balance, so as to maximize the accumulation of net photosynthetic products. 2.3 Impact on root development and nutrient uptake On the other hand, density affects the growth and development of individual plants and the source-sink relationship. Under sparse planting conditions, there is ample tillering space for individual plants, which can produce more tillers and large panicles, but the number of panicles in the group may be insufficient; under dense planting conditions, the number of tillers per plant decreases, but the number of effective panicles per unit area increases (Zhu et al., 2016; Wei et al., 2021). According to the theory of "compensation effect" of rice, within a certain range, the group yield is stable to density, that is, when the plant density increases, the number of panicles and grains per plant decreases, but the increased number of panicles can often make up for the individual losses, so that the total yield remains unchanged or slightly increases. However, when the density is too high, individual development is severely inhibited, ineffective tillers and spikelet abortion increase within the group, and yield decreases, which is called the "inverted U-shaped" density-yield relationship. For example, Wei et al. (2021) found through a seeding test under drought cultivation that rice yield first increased and then decreased with seeding, reaching a peak at a seeding rate of 195 kg/ha, at which time the number of spikes and the number of grains per mu increased in a coordinated manner. When the density exceeds this, the yield decreases due to poor
Rice Genomics and Genetics 2025, Vol.16, No.2, 71-85 http://cropscipublisher.com/index.php/rgg 73 individual development. This verifies that density optimization requires a balance between group advantages and individual vitality to achieve a match between the source (leaf photosynthetic products) and the sink (grain capacity). Density also involves the theory of rice population quality. High-yield populations usually require sufficient seedlings in the early stage, reasonable reduction of ineffective tillers in the middle stage, and maintenance of functional leaf activity in the later stage, that is, "enough seedlings in the early stage, stable spikelets in the middle stage, and strong seeds in the later stage" (Huang et al., 2024). If the density is too low, it is difficult to form a sufficient seedling population in time, and if it is too high, the canopy will be closed in the middle stage and prone to premature aging. Chen et al. (2014) pointed out that there is an interaction between planting density and nitrogen application level, which has a significant impact on population dynamics: moderate density combined with medium nitrogen fertilizer level can establish a high-yield population structure with appropriate number of panicles and slow decay of population leaf area. This theoretical basis shows that density optimization often needs to be combined with fertilizer management, and the optimal configuration between panicle number and panicle size can be achieved by cultivating strong seedlings and controlling tillering. The theoretical basis for optimizing rice planting density is: by adjusting the basic number of seedlings, the population structure is promoted to develop in the direction of having sufficient panicles without damaging individual capabilities, so as to achieve the unity of "maximum productivity of the population" and "optimal function of the individual". This process involves multiple mechanisms such as light energy utilization, growth resource allocation, and source-sink coordination. It is necessary to comprehensively consider variety characteristics and environmental conditions to determine the optimal density range. 3 Analysis of the Impact on Growth and Development Planting density directly determines the individual growth environment and group ecological conditions of rice, and has a significant impact on the morphological construction, physiological characteristics and growth and development process of the plant. It is mainly reflected in tillering dynamics, plant structure, photosynthetic performance and lodging resistance. 3.1 Tiller dynamics and productive panicles Density affects tillering occurrence and ear formation rate. Generally speaking, reducing planting density (sparse planting) is conducive to increasing the number of tillers per plant, but too many tillers are often difficult to all ear, resulting in an increase in the proportion of ineffective tillers. On the contrary, increasing density (dense planting) can inhibit the number of tillers per plant, prompting limited tillers to stagnate earlier, thereby increasing the tillering ear formation rate. In the study of Yang et al. (2019), the number of tillers per plant of machine-transplanted late rice was significantly reduced under low nitrogen combined with dense planting treatment, but the total number of ears in the group was equivalent to that of conventional treatment, and the ear formation rate increased by about 5 percentage points, indicating that dense planting helps control ineffective tillers and optimize the group ear structure. Under mechanical transplanting conditions, close planting is often combined with the "one seedling per hole" technology to reduce the number of basic seedlings per pile but increase the number of holes. It is reported that compared with the conventional sparse planting of multiple seedlings per hole, single dense planting can reduce the maximum number of tillers per plant by about 20%, while the number of effective ears is only slightly lower or equivalent, so the ear efficiency (effective tillering rate) is significantly improved. It can be seen that close planting achieves the effect of streamlining individual tillers and improving ear formation efficiency by "controlling tillers with groups". 3.2 Plant height, lodging, and canopy structure Density changes plant type and canopy structure. Under sparse planting conditions, the plant spacing is large, individual competition is small, and individual plants can form a relatively open plant type and thick stems. When densely planted, the plants tend to be upright and compact, which is manifested by increased plant height, thinner stem base, and narrower and upright leaves. Hu et al. (2023) showed that increasing the planting density
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