Effects of Different Planting Patterns on Coordinated Development of Source–Sink and Quality Traits in Cotton

The synergistic regulatory mechanism of current planting patterns on cotton agronomic traits, boll source–sink development and fiber quality remains unclear. Therefore, this study used 11 upland cotton parents and 36 F1 progenies as materials. Three planting patterns, namely, one film–three rows, one film–four rows and one film–six rows, were established from 2024 to 2025. The dynamic changes in the boll morphology and dry-fresh-weight accumulation of each boll component were monitored at eight stages from 10 to 60 days after anthesis, and agronomic traits and fiber quality were measured simultaneously. The Logistic growth model was adopted to fit cotton boll growth parameters to analyze the regulatory effects of planting patterns on the developmental process and dry-matter accumulation of upland cotton. The results showed that boll morphological stability gradually decreased with the increase in planting density. The maximum cumulative boll volume (Wm) under the one-film–three-rows pattern ranged from 29.19 to 30.97 cm3, higher than those under one film–four rows (28.35–30.77 cm3) and one film–six rows (28.74–30.86 cm3). Vegetative growth indicators, including plant height, height of the first fruiting node and number of fruiting branches, declined with increasing density. The one-film–six-rows treatment exhibited a significantly higher proportion of empty fruiting branches and a lower boll-setting rate. The one-film–three-rows pattern presented prominent single-boll sink capacity, yet suffered insufficient population photosynthetic supply, leading to assimilate allocation biased toward vegetative organs. Under high-density competition stress, the one-film–six-rows pattern possessed poor source–sink stability and inhibited dry-matter accumulation in reproductive organs. The one-film–four-rows pattern achieved the highest dry-matter translocation efficiency from boll shell to cottonseed and fibers, with the maximum cumulative fiber dry weight (Wm) of 2.40–2.62 g, and obtained optimal fresh-weight accumulation and allocation of fibers. Synthesizing all indicators, the one-film–four-rows pattern is more suitable for cotton growth in southern Xinjiang, which can balance population boll-setting potential and boll dry-matter allocation efficiency. These results are only derived from two-year field-located experiments in southern Xinjiang. Multi-site trials are required in further research to clarify the applicable scope of this cultivation pattern in other cotton-producing regions.