Field Crop 2025, Vol.8, No.4, 195-203 http://cropscipublisher.com/index.php/fc 199 cotton, the row spacing and density need to be specially designed to distribute light, water and nutrients more reasonably. Generally speaking, medium density combined with flexible line spacing is more appropriate (Li, 2024; Zhang et al., 2025). In addition, choosing the right variety is also very important. Limited-growth and compact varieties are suitable for high-density planting, which facilitates mechanized operation. For varieties with unlimited growth or vigorous growth, a larger plant spacing should be maintained to prevent excessive growth and facilitate mechanical harvesting (Lakshmanan et al., 2025). Only by integrating these management methods with the local natural conditions can cotton be grown in large quantities and of high quality, achieving sustainable production. 6 Case Studies: Regional Practices in Density and Row Configuration Optimization 6.1 High-yield cultivation practices in the Yellow River cotton-growing region of China In the Yellow River Basin, when growing cotton, special attention should be paid to the arrangement of density and row spacing, especially when short-season cotton is planted and mechanical harvesting is used. Field experiments have shown that if 112 500 cotton plants are planted per hectare and the wide and narrow row arrangement (66 cm + 10 cm) is adopted, a relatively high and stable seed cotton yield can be achieved, with the maximum reaching 3 832 kilograms per hectare. Under this planting method, the plant height and leaf area index (LAI) of cotton are higher than those under low-density planting. At harvest time, wide and narrow rows can still maintain a better canopy structure and a higher LAI, making the yield more stable. Although the quality of the fibers will not change much, this method is more suitable for mechanical harvesting and is also more conducive to stable production (Li et al., 2023). 6.2 Optimization practices of planting density and row configuration in the southern United States In the southern United States, the study compared different planting densities and sowing methods, such as hole sowing and row sowing with a row spacing of approximately 96.5 cm. The results show that in hole sowing, high density (up to 152 833 plants per hectare) can increase the lint cotton yield to the maximum (1 465 kilograms per hectare). Only when the density is too low will the output decline. As the density increases, the height of the plants will increase, but other growth and fiber quality indicators change little. If the plants are evenly distributed, reducing the sowing amount can also save costs and will not affect the fiber quality (Siebert et al., 2006). In addition, interlaced planting (such as 2x1 interlaced, with a row spacing of 76 cm) can also maintain yield and income, while reducing costs and having a minimal impact on fiber quality (Larson et al., 2009). 6.3 Studies on narrow row spacing and fiber quality improvement in Central Asia In these arid regions of Central Asia, research has found that growing cotton in narrow or ultra-narrow rows can increase yields and reduce input costs (Figure 2) (Ye et al., 2021). For instance, by adopting a high-density and narrow row approach, the yield of seed cotton can be significantly increased. Therefore, this method is also recommended to replace the traditional planting model. However, if the density is too high, it may cause the quality of the fibers to deteriorate, such as a decrease in the fineness of the fibers. Therefore, while pursuing output, it is also necessary to pay attention to maintaining fiber quality, and a suitable balance needs to be found between the two. Under this more intensive planting method, the selection of varieties becomes particularly important. Only by choosing the right variety can the output be increased while maintaining the quality of the fiber (Goren and Tan, 2024). 7 Molecular and Physiological Mechanisms 7.1 Effects of density and row configuration regulation on the expression of photosynthesis-related genes The density and row spacing of planting can affect the photosynthesis of plants and also influence the expression of related genes. If they are planted too densely, the leaves will block each other, and the photosynthesis of the leaves on the vegetative branches will be weakened. In this way, the content of chlorophyll will decrease, and the activity of RuBP carboxylase will also decline, eventually leading to the inhibition of photosynthesis. Some key photosynthetic genes will be downregulated, and the carbohydrates in shaded leaves will also decrease. If the line spacing is arranged reasonably, for instance, by using uniform line spacing and moderate density, the sunlight can be distributed more evenly. In this way, the leaves in the middle and lower layers of the canopy can also maintain
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