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
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