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).
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