Rice Genomics and Genetics 2025, Vol.16, No.4, 180-198 http://cropscipublisher.com/index.php/rgg 189 mechanized transplanting to achieve standardized transplanting of seedlings. The machine transplanting specifications vary according to the variety type: the row spacing of indica and japonica hybrid rice is 30 cm×22 cm, and there are 2-3 seedlings per cluster; the row spacing of conventional late japonica rice is 30 cm×16 cm, and there are 4-5 seedlings per cluster. This fixed-width narrow row spacing mode takes into account the needs of different types of varieties for population density. Mechanical transplanting ensures uniform spacing and seedling numbers, reduces manual errors, and is conducive to group ventilation and light transmission and resource utilization. At the same time, machine transplanting improves transplanting efficiency, and 1 hectare can be transplanted in 5 hours, greatly reducing labor intensity (Vijay et al., 2024). More importantly, mechanized cultivation methods can also improve rice plant type and lodging resistance. Studies have shown that compared with manual blanket seedling transplanting or direct seeding, rice transplanted by pot seedling machine has shortened 1-3 internodes at the base, thickened stems, improved internode fullness, significantly increased stem bending moment, and reduced lodging index. The practice of this demonstration also verified this point: the machine-transplanted seedlings have deep roots and neat tillers, and the new varieties generally have thick stems, and basically no lodging occurs during maturity. Mechanized transplanting also promotes early group formation. The machine-transplanted fields of "Yongyou 33" and other varieties reached a maximum of 170 000 seedlings per mu 10 days after transplanting, and tillering started quickly. This creates conditions for making full use of the growth period and increasing the number of ears per mu. Of course, mechanized cultivation also requires that seedling cultivation be adapted to field engineering, such as leveling the land and managing the water layer reasonably, to ensure the quality and survival rate of transplanting. The combination of substrate seedling cultivation and machine transplanting mode has achieved mechanization and standardization of the entire rice production process. It not only improves cultivation efficiency and reduces costs, but also optimizes group structure and enhances the plant's resistance to lodging. For the large-scale promotion of new varieties, this supporting model can ensure that the yield-increasing advantages of new varieties are fully utilized. Based on this demonstration, Yuhang District and other places have promoted the rice machine-transplanted stacked tray seedling technology, providing strong support for improving the quality and efficiency of regional grain production. 5.2 Effectiveness of the “one basal, one top” controlled-release fertilizer strategy The demonstration base adopted the efficient fertilization mode of "one base and one topdressing" of controlled-release fertilizer in fertilization management, that is, a one-time basal application of controlled-release fertilizer before transplanting, and a small amount of topdressing of ear fertilizer according to the seedling conditions during the tillering period. The specific method is: when tilling and preparing the land before transplanting, 40 kg of controlled-release compound fertilizer (N-P-K ratio 25-12-15) per mu is applied as basal fertilizer, and 7.5 kg/mu of slow-release fertilizer containing 30% nitrogen is applied as tillering fertilizer about 10 days after transplanting, and 12.5 kg of compound fertilizer is applied as ear fertilizer before heading. This scheme realizes the centralized slow-release supply of nitrogen fertilizer, which greatly reduces the number of fertilization and labor input compared with traditional split-time fertilization. More importantly, the one-time basal application of controlled-release fertilizer can simultaneously meet the nutrient requirements of rice at all growth stages, reduce nutrient leaching and volatilization, and improve the utilization efficiency of nitrogen fertilizer (Chen et al., 2020). Studies have shown that compared with conventional urea application in batches, one-time application of polymer-coated urea can significantly increase rice yield under equal nitrogen conditions, such as an increase of about 10%-16% in early rice and about 5%-14% in late rice. The demonstration results also show that the fields using the "one base and one topdressing" technology of controlled-release fertilizer have neat and effective tillering, moderate and light leaf color, no excessive greed for green, normal color change in the later stage, and obvious yield increase effect. The analysis shows that controlled-release fertilizer slowly releases nitrogen, meets the nutrient needs of rice in key periods such as jointing and heading, and avoids excess nitrogen in the seedling stage and late stage, which is conducive to the formation of higher heading rate and fruiting rate. Improving the efficiency of nitrogen fertilizer utilization not
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