Rice Genomics and Genetics 2025, Vol.16, No.2, 71-85 http://cropscipublisher.com/index.php/rgg 80 phenomenon of high yield and low benefit may occur; on the contrary, excessive cost saving may miss the opportunity to increase production. Therefore, the unit cost benefit or benefit-cost ratio should be used as the evaluation indicator. In existing studies, Zhang et al. (2023) found through drone dense planting experiments that when the density increased from 150 to 300 g/tray, the rice output per kilogram of seeds gradually decreased, and the benefit-cost ratio reached the highest at 250 g/tray, and the ratio decreased when the density increased further. This type of analysis helps to find the density with the best economy rather than only the best yield. Optimizing planting density can usually improve the economic benefits of rice production, but it is necessary to balance the relationship between increased yield benefits and increased input. The yield benefits brought by moderately increasing density are often greater than the increase in seeds and other costs, and can also improve resource utilization efficiency and reduce certain risk costs, thereby increasing net profit. However, density beyond a reasonable range will cause diminishing returns or even reduce net income. Therefore, when promoting the technology of dense planting and yield increase, we should emphasize supporting cultivation and economic accounting to ensure that farmers can "increase their input by a little and get double the output" and achieve real high yield and high efficiency. For example, conducting typical surveys of rice farming systems in different regions and optimizing planting density parameters with the goal of maximizing economic benefits will be conducive to the sustainable adoption of technology and increasing income and efficiency of food production. 6 Case Study: Practical Enlightenment of Regional Application In order to better apply the above theories and influencing laws to production practice, the following takes the plain rice area in Nanchang, Jiangxi and the hilly rice area in Leshan, Sichuan as examples to explore the implementation effect and experience enlightenment of planting density optimization under different ecological conditions. 6.1 Density and lodging resistance practice in the double-season rice area in Nanchang, Jiangxi Nanchang is located in the central plain of Jiangxi, with a warm and humid climate and a long history of double-season rice planting. The early rice in this area is heading and filling in the plum rain season, and often encounters high temperature, high humidity and rainy weather. Plant leggy growth and lodging are one of the main problems that limit yield. Traditionally, local farmers often increase the basic seedlings in order to achieve high yields. The hand-planting density of early rice is generally above 20 holes/m2, with 2-3 plants per hole. However, this method is prone to lead to group closure, elongation of the base internodes, and large-scale lodging in the event of strong winds and rainstorms, which seriously affects yield and harvest. In recent years, Jiangxi Agricultural University and local agricultural technology departments have cooperated to carry out double-season rice density optimization cultivation experiments to promote the technology of "appropriately reducing density and cultivating strong seedlings". Taking Li (2020)’s research experiment as an example, in the early rice fields in the suburbs of Nanchang, three seeding rates of 12.5 kg, 15 kg and 25 kg per mu were set, which was equivalent to a basic seedling density of about 800 000, 1 million and 1.7 million seedlings per hectare. The results showed that the population of the medium seeding rate (15 kg/mu) treatment grew neatly and robustly, with 320 effective ears per square meter, which was slightly lower than the high seeding rate treatment by 5%, but the number of grains per ear was 8% higher, the fruiting rate increased by 2 percentage points, and there was no significant difference in the final yield. More importantly, the high seeding rate treatment suffered from varying degrees of lodging in both years of the experiment, with a lodging rate of 15%-20% during the fruiting period, while the medium seeding rate treatment had basically no lodging. Although the low seeding rate treatment had thicker stems, the number of ears was less and the yield was slightly reduced. In terms of comprehensive benefits, the medium seeding rate (moderately reduced density) treatment achieved the highest benefits. Therefore, researchers recommend that the sowing rate of Nanchang double-season early rice direct seeding should be about 15 kg per mu, supplemented by soil testing and formula fertilization and growth regulator control, which can effectively balance the number of ears and ear weight, reduce the risk of lodging, and achieve stable and increased yields. This practical case shows that in areas with high lodging risk, reducing the planting density to enhance individual resistance to lodging and improve group robustness is a practical and effective way. After the promotion of this
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