Field Crop 2025, Vol.8, No.6, 284-292 http://cropscipublisher.com/index.php/fc 284 Research Insight Open Access Optimizing Planting Density and Sowing Date for Mechanized Direct-seeded Rice in Subtropical Regions Xinguang Cai, Yaodong Liu Modern Agricultural Research Center, Cuixi Academy of Biotechnology, Zhuji, 311800, Zhejiang, China Corresponding email: yaodong.liu@cuixi.org Field Crop, 2025, Vol.8, No.6 doi: 10.5376/fc.2025.08.0029 Received: 01 Oct., 2025 Accepted: 13 Nov., 2025 Published: 02 Dec., 2025 Copyright © 2025 Cai and 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: Cai X.G., and Liu Y.D., 2025, Optimizing planting density and sowing date for mechanized direct-seeded rice in subtropical regions, Field Crop, 8(6): 284-292 (doi: 10.5376/fc.2025.08.0029) Abstract In subtropical rice-growing areas, the problems of rising labor costs and tight water resources have become increasingly prominent, promoting the rapid development of Mechanized Direct-seeded Rice (MDSR) technology. However, as the key factors affecting the yield and stability of mechanical direct seeding rice, the optimal combination of sowing period and planting density has not yet been systematically studied and precisely guided in subtropical regions. This study aims to clarify the influence mechanisms of different sowing periods and planting densities on the growth and development, population structure, yield composition and resource utilization efficiency of mechanically direct-sown rice in subtropical regions, explore their interaction relationships, and systematically evaluate the physiological and ecological performance of various combinations of sowing periods and densities through field trial cases conducted in South China. Combined with meteorological data and yield factor analysis, efficient and stable production plans were screened out, striving to provide a scientific basis for the regionalized cultivation of mechanical direct seeding rice. This research not only enriches the theoretical system of efficient rice cultivation, but also provides practical support for promoting the regional adaptation of mechanized and intelligent green rice cultivation, which is of great significance for ensuring food security and achieving sustainable agricultural development. Keywords Rice (Oryza sativaL.); Mechanical live streaming; Planting density; Sowing period; Output optimization 1 Introduction Rice (Oryza sativa L.) has always been one of the staple foods in subtropical regions, but in recent years, the difficulty of growing it has been increasing. The labor force is decreasing, water sources are not as stable as before, and the climate is always "throwing a tantrum". The traditional practice of relying on manual transplanting, excessive irrigation and high cost is no longer able to cope with the current situation. Especially against the backdrop of the continuous flow of young labor force to cities and the increasing difficulty in farmland management, the sustainability of this approach is being tested. To address these issues, many places have begun to experiment with the practice of directly sowing seeds instead of raising seedlings for transplanting - direct seeding rice (DSR). Labor-saving, water-saving, and more resilient in the face of some extreme weather (Jat et al., 2022). However, not all direct seeding rice systems can meet expectations. The mechanized type, especially new technologies such as row seeding and drone broadcasting, currently seem to have more potential for development. Methods like mDSR (Mechanized Direct Seeding Rice) not only help farmers save seeds and fertilizers, but also ensure uniform emergence and are easy to manage. Many studies have also found that its output is comparable to that of traditional methods, and sometimes even higher. Moreover, it has low cost, few diseases, light lodging, and can even significantly reduce greenhouse gas emissions (Wang et al., 2021). From a broader perspective, it meets the demands of green agriculture and is also suitable for coping with extreme climates, improving the utilization rate of nitrogen fertilizers, reducing carbon emissions and maintaining stable production (Yang et al., 2022; Zhou et al., 2023). This study will review the current situation and challenges of rice cultivation in subtropical regions, analyze the development and advantages of mechanical direct seeding technology, and determine the optimal planting density and sowing date in the mechanical direct seeding system that can maximize yield, resource utilization efficiency and sustainability. By integrating recent research and field trials, this study aims to provide practical suggestions
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