Field Crop 2025, Vol.8, No.4, 195-203 http://cropscipublisher.com/index.php/fc 198 improving the fiber quality in these areas. During the development stage of cotton bolls, maintaining LAI at around 2.0 can balance the canopy structure and achieve the optimal photosynthetic efficiency. 4.2 Population-level growth balance and mechanisms of yield formation The planting density and row spacing of cotton will affect the growth state of the entire population, as well as the utilization efficiency of water and nutrients, and thereby influence the yield. If medium density is used, along with uniform row spacing or six-row spacing, cotton can better utilize water and heat. This approach can help accumulate more biomass and also increase the harvest index. Under this configuration, the number and size of cotton bolls can be kept balanced. The water use efficiency (WUE) has been improved, and the output can also be more stable, or even increase. This combination is particularly suitable for arid areas or cotton fields that use drip irrigation. However, if the density is too high or the row spacing is unreasonable, there will be too much competition among the cotton. This will cause the cotton bolls to become smaller, lose weight, have a lower harvest index, and also deteriorate the utilization of water and nutrients (Dong et al., 2025). 4.3 Coupling effects on improving fiber quality When there is sufficient moisture, using a moderate density with uniform row spacing can significantly improve the fiber quality of cotton, such as making the fibers longer and stronger. This combination works particularly well for the cotton bolls in the middle and lower layers of the canopy. Although high-density planting with wide and narrow rows can increase yield, because cotton is planted too densely, the lower leaves cannot be exposed to sunlight, which can easily lead to poor fiber quality. On the contrary, an appropriate density combined with uniform row spacing not only makes the distribution of cotton bolls more reasonable and ensures more even light exposure, but also enhances the maturity and consistency of the fibers. These studies indicate that as long as the density and row spacing are arranged according to the local water resource conditions, it is possible to achieve both high yield and good fiber quality simultaneously. 5 Regulation by Environmental and Management Factors 5.1 Influence of climatic conditions on the optimization of density and row configuration Temperature, light and rainfall can affect the suitable density and row spacing of cotton. In places with abundant sunlight and heat, such as Xinjiang, using medium to high density combined with uniform row spacing can enable cotton to make better use of sunlight, improving the efficiency of radiation utilization (RUE) and yield. However, the weather conditions change every year, which can affect the growth and yield stability of cotton. Therefore, the density and row spacing cannot be fixed. They should be appropriately adjusted according to the climate of the current year to reduce the impact of climate change (Xin et al., 2025). In arid or semi-arid areas, high density has certain benefits. Because cotton grows fast, the canopy can close quickly, which can reduce the evaporation of soil moisture and also allow the cotton to mature earlier. However, if the density is too high, it will also cause excessive competition among plants, with leaves blocking each other, which will instead affect their growth. Therefore, the density should be well controlled, neither too high nor too low (Manibharathi et al., 2024). 5.2 Regulatory role of soil fertility and water availability The amount of nutrients in the soil and the sufficiency of moisture will both affect the planting effect of density and row spacing. If the moisture content is relatively abundant, using medium density with uniform row spacing (for example, 76 cm) will result in better cotton yield and fiber quality, and water will also be used more efficiently (WUE) (Chen et al., 2019; 2022). If there is not enough water, you can choose wide and narrow rows (for example, 66+10 cm) along with a slightly higher density. This combination can better utilize the water in the soil. Even with a small amount of irrigation, the yield can still be stable (Zuo et al., 2023). Apart from water, the fertility of the soil is also very important. High-density planting can help cotton absorb nutrients better and also improve nitrogen utilization efficiency (NUE). However, if the fertilizer is insufficient, the nutrients will be used up quickly, which may instead lead to a deterioration in fiber quality (Wu et al., 2024). 5.3 Compatibility with cropping systems and cultivar types The setting of density and row spacing also depends on the specific planting method adopted and the variety planted. For instance, in some intercropping systems, such as the combination of cotton and cumin or jujube and
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