Rice Genomics and Genetics 2025, Vol.16, No.2, 71-85 http://cropscipublisher.com/index.php/rgg 81 technology in Nanchang, the average lodging rate of early rice in multiple demonstration fields has dropped from more than 10% in the past to less than 3%, with a reduction of about 40 kg per mu, equivalent to reducing losses and increasing profits by about 100 yuan (Liao et al., 2023). Farmers reported that the density optimization technology is simple and easy to use, does not require additional equipment investment, and is easy to accept. At present, the planting density of early rice in this area has shown a significant downward trend compared with ten years ago, and the group quality and yield stability have been significantly improved. This shows that density management has played an important role in updating cultivation concepts and improving risk resistance in traditional rice areas. 6.2 Application of dense planting and machine transplanting in the hilly area of Leshan, Sichuan Leshan City is located on the southwestern edge of the Sichuan Basin. It is dominated by hills and plains. There are many scattered rice fields and the degree of mechanization started late. The rice cultivation in this area is mainly medium-season rice or one-season late rice, and most of the varieties are hybrid indica rice. In the past, due to the long seedling age of the seedling field and the low transplanting density (generally about 16 holes/m2, 4-5 plants per hole), the number of panicles in the group was insufficient and the high-yield potential was not fully utilized. According to a survey by the local Academy of Agricultural Sciences, before 2015, the average number of panicles per mu of rice in Leshan was only about 1.6 million, and the yield per unit area hovered around 500 kg for a long time. The experience of Hunan and other places shows that the machine transplanting cultivation technology of "one hole, one seedling, dense planting and shallow transplanting" can significantly increase the yield of super rice. To this end, the Leshan Agricultural Technology Extension Center has introduced and promoted the dense planting and machine transplanting technology since 2018, and verified its yield-increasing effect by building demonstration plots. Taking the demonstration in Wutongqiao District in 2019 as an example, the widely adaptable hybrid rice variety "Yixiangyou 2115" was selected to compare the differences between traditional manual planting (15 holes/m2×4 books per hole) and dense planting machine planting (30 holes/m2×1 book per hole). Under the same fertilizer and water management, the number of effective ears per mu in the dense planting machine planting treatment reached about 2.2 million ears, 400 000 more than the control; although the total number of grains per ear dropped from 150 grains in the control to about 130 grains in the dense planting treatment, the fruit set rate of the two was similar and there was no difference in thousand-grain weight. In the end, the dense planting machine planting treatment had an acreage yield of 837 kg, while the control was 745 kg, an increase of 12.3%. At the same time, the plant height of the dense planting machine planting group was slightly lower, the coarseness and hardness of the stems were comparable to the control, no lodging occurred, and the appearance quality of rice, such as the rate of whole polished rice, was not significantly different from the control. Xie et al. (2016) concluded that the key to the success of dense planting and single machine transplanting in the hilly areas of southwest China such as Leshan is: first, mechanized seedling cultivation ensures the quality of seedlings and the implementation of small seedling machine transplanting; second, the matching of wide and narrow row planting mode (such as alternating 30 cm wide row spacing + 13 cm narrow row spacing) improves the ventilation and light conditions of dense planting groups. After three consecutive years of practice in the Leshan demonstration area, the average per mu yield of dense planting and machine transplanting rice increased by 8%-15% compared with the traditional method. At the same time, 0.5 kg-1 kg of seeds were saved per mu, and there was basically no need to supplement seedlings, which greatly reduced labor and achieved significant overall benefits. At present, this technology has been promoted to tens of thousands of mu in Leshan City, becoming a new highlight of local grain production increase. The inspiration we can get from the Leshan case is that in hybrid rice areas with medium soil fertility and average tillering ability, by increasing the planting density and adopting single seedling transplanting, the potential of large panicles of hybrid rice can be fully utilized while significantly increasing the number of panicles and achieving a breakthrough in high yield. At the same time, with a reasonable planting layout, the negative effects of dense planting can be avoided. This has a strong reference significance for similar areas such as Sichuan hills. During the promotion process, we should focus on solving the technical bottlenecks of mechanical transplanting (such as the strength of the seedling board and the flatness of the field), and adjust the row spacing and basic number of seedlings according to local conditions. For example, the field test
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