Rice Genomics and Genetics 2025, Vol.16, No.2, 71-85 http://cropscipublisher.com/index.php/rgg 79 compared with the increase in yield. It should be noted that in the case of direct seeding or seedling throwing, excessive sowing will significantly increase seed costs and labor costs, which may not be economically cost-effective. Therefore, the balance point of increased yield vs. increased costs should be calculated. Li (2020) compared the economic benefits of different sowing amounts for double-season direct seeding rice: the results showed that the yield and income of the medium sowing amount (15 kg per mu) were higher than those of the low sowing amount, and only 0.2 kg of seeds were required for each additional kg of rice, and the input-output ratio was relatively high; while the excessive sowing amount (25 kg) slightly increased the yield, but the increase in seed input exceeded the output value gain, and the net income decreased. It can be seen that there is an optimal density that maximizes the marginal output per unit input. 5.3 Optimal economic density range Density optimization affects the efficiency of fertilizer and plant protection inputs. Reasonable close planting can often improve fertilizer utilization, which may reduce the demand for fertilizer and thus save costs. The experiment of Wang et al. (2018) showed that when the sowing rate of 195 kg/ha was combined with 140 kg/ha of nitrogen, the same high yield was achieved with a reduction of about 18% in nitrogen fertilizer use, and the fertilizer cost was reduced compared with the traditional nitrogen application of 170 kg/ha + low sowing rate. This is beneficial to economic benefits. In addition, the weed suppression effect of densely planted fields is better, which can reduce the cost of weed control; but excessively dense planting leads to aggravated diseases, which will increase pesticide input and even cause production losses, thus negatively affecting the benefits. Therefore, it is necessary to consider the changes in input comprehensively. Only by combining moderately dense planting with scientific fertilizer and pesticide management can we achieve "increased production without increased cost" or "increased production with slightly increased cost and greater increase in benefits". Risk factors such as the risk of lodging and reduced yield are also related to density, which affects economic benefits. Lodging will seriously affect the yield and harvest quality, causing direct economic losses to farmers. Too high density often increases the probability of lodging, bringing potential risk costs. Correspondingly, slightly reducing the density can improve the resistance of the group to lodging and reduce the probability of yield reduction due to lodging, which is equivalent to a risk-averse benefit. Jiang et al. (2021) showed that in hot and rainy areas, the implementation of nitrogen reduction and dense planting technology increased the density, but by simultaneously reducing the growth potential of nitrogen fertilizer, the stalk strength was maintained, lodging did not occur, and the income was stable. This suggests that reasonable density can reduce the probability of disaster losses to a certain extent and have a positive effect on long-term average income. In addition, appropriate density can also reduce ear loss and mechanical damage during the harvesting process, and increase the yield of commercial rice, which is also one of the economic benefit factors. A brief economic analysis is conducted using the double-season rice in Nanchang, Jiangxi as an example: under the control density (traditional) conditions, the yield of early rice per mu is about 500 kg, the rice income is 1 250 yuan, the seed cost is 40 yuan, and the net income is 1 210 yuan; by optimizing the sowing density and the basic seedlings of the rice seedlings, the yield per mu is increased to 530 kg, the income is 1 325 yuan, the seed cost is 50 yuan, and the lodging loss is reduced by about 30 yuan, which is included in the income. The net income is about 1 305 yuan, which is 95 yuan more than the control, an increase of 7.9%. It can be seen that density optimization has achieved a considerable increase in net income while maintaining or slightly increasing the cost. This benefit is of great economic significance when planted on a large scale. Looking at the hybrid rice in the hilly area of Leshan, Sichuan, due to the use of single-plant dense planting machine transplanting technology, the seedling cost is slightly higher than the conventional one, but the yield per mu is increased from 600 kg to 650 kg, and some weeding costs are saved at the same time. The overall income per mu increased by nearly 150 yuan, showing a good rate of return of "high input brings higher output". It should be emphasized that the economic benefit evaluation should take into account the cost structure and goals of different entities (farmers/cooperatives). If only the highest yield is pursued without considering the cost, the
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