Field Crop 2025, Vol.8, No.4, 195-203 http://cropscipublisher.com/index.php/fc 196 This study reviewed the effects of planting density and row spacing on cotton yield and fiber quality, and sorted out the latest research results at home and abroad. The article analyzes the physiological and agronomic mechanisms behind these influences, compares the performance of various densities and planting methods under different environmental and management conditions, and also puts forward some suggestions for optimizing cotton cultivation. This study aims to provide some practical ideas for growers, ensuring yield while also enhancing fiber quality and improving overall economic benefits. 2 Effects of Planting Density on Cotton Yield and Quality 2.1 Regulation of photosynthetic efficiency and canopy structure under different planting densities Planting density has a significant impact on the canopy structure of cotton and also alters light interception, photosynthetic efficiency and the microclimate in the field. Moderate or high density can increase the leaf area index (LAI), allowing reproductive organs to obtain more light energy and accumulate more biomass, thereby enhancing yield. However, if the density is too high, the canopy will close prematurely, and the lower leaves will not receive sufficient light, intensifying the competition for resources. The result may be a decrease in photosynthetic efficiency and premature senescence of the leaves (Yang et al., 2014; Khan et al., 2017). Appropriate density can maintain balance, ensure reasonable light distribution and suitable canopy temperature, which is conducive to efficient photosynthesis and normal growth (Khan et al., 2020). 2.2 Effects of density on boll distribution and fruiting characteristics When the planting density increases, the number of cotton bolls per mu will be greater, but the number of cotton bolls on each plant will decrease, and the weight of each boll will also drop. High density is conducive to the rapid closure of the canopy, and the plants mature earlier. However, the competition is also more intense, and the cotton bolls will become smaller and concentrate on the upper and distal branches. When the density is low, the plants have more branches, more cotton bolls per plant, and larger cotton bolls. However, due to the smaller number of plants, the total yield may decrease (Li et al., 2020). An appropriate density can optimize the number of cotton bolls and the growth rate of fruits, which is directly related to the total output. 2.3 Relationship between planting density and fiber quality traits Different fiber quality properties respond differently to density. Higher density generally increases the yield of lint cotton, but due to intensified competition and changes in sucrose metabolism, the fiber strength, Macron value (fineness), and maturity may decline (Jalilian et al., 2023). At medium to high densities, the fiber length may be slightly longer, but at low densities, the strength and fineness of the fibers are often better. The role of genotype in fiber quality is also quite obvious, and reasonable density management helps to maintain or even enhance quality potential. If the density is too high, it will also reduce the activity of sucrose synthase and the cellulose content in the fiber, resulting in a decrease in the Macron value and maturity (Meng et al., 2016; Zhang and Wang, 2024). 3 Mechanisms of Row Configuration 3.1 Effects of wide-narrow row configuration on canopy structure, ventilation and light interception Different row spacing arrangements can alter the structure of the cotton canopy and also affect the lighting and ventilation conditions. Both wide and narrow line spacing (such as 66+10 cm) and uniform line spacing (such as 76 cm) can have a significant impact. High-density and wide-narrow rows can enable the canopy to absorb more photosynthetically active radiation (PAR), resulting in higher photosynthetic efficiency and an increase in the biomass of cotton bolls, especially during the critical growth period of cotton. However, if uniform row spacing is combined with appropriate density, light can more easily penetrate to the middle and lower layers of the canopy, and both the leaf area index (LAI) and the overall photosynthesis of the canopy (CAP) will increase. This not only benefits the development of the lower cotton bolls but also improves the quality of the fibers. Under reasonable irrigation conditions, it can also ensure a relatively high yield (Hu et al., 2021). In addition, equal row spacing can also increase the light transmittance in the middle and upper layers, making the fruit branches grow more evenly and the distribution of cotton bolls more reasonable (Figure 1) (Gao et al., 2024).
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