Effects of planting density and row spacing configuration on dry matter accumulation and distribution, nutrient...

Dry matter accumulation and distribution constitute the essential material basis for crop yield formation, directly impacting both yield and quality development. Nonetheless, the effects of planting density on dry matter accumulation, distribution, and nutrient uptake in cotton across various row spacing configurations remain ambiguous.

This study conducted a two-year field experiment utilizing the cotton cultivar "Tahe 2". In 2024, a single-factor trial was adopted with three row spacing treatments: same row spacing (S3), wide-ultra-narrow row spacing (S4), and wide-narrow row planting (S6). In 2025, a two-factor split-plot design was used: main plots were the three row spacing patterns (S3, S4, S6), and subplots were three planting densities: 135 000 plants ha^-1 (D1), 180 000 plants ha^-1 (D2), 225 000 plants ha^-¹ (D3). We investigated leaf area index (LAI), dry matter accumulation and distribution, nutrient content, and yield.

In 2024, S6 showed the highest leaf area index (LAI) and dry matter accumulation (p< 0.05). In 2025, LAI and dry matter accumulation increased significantly with increasing plant density (p< 0.05). The dry matter partitioning ratio to reproductive organs increased with growth. Row spacing and planting density significantly affected leaf nutrient contents; upper-leaf nitrogen (N) and potassium (K) first increased then decreased, while middle- and lower-leaf N and leaf phosphorus (P) at all positions declined gradually. Boll number per plant decreased with increasing density, whereas yield was significantly affected by their interaction (p< 0.05). The highest yield was found in S6 in 2024 and S6D2 in 2025. Two-year experiments indicated that S6 combined with 180,000 plants ha^-¹ optimized population structure, improved resource use efficiency, and increased cotton yield.

Among the three row spacing configurations tested, the medium planting density of 180,000 plants ha^-1 under the wide-narrow row planting pattern (S6) optimized the leaf area index, enhanced population dry matter accumulation, and improved distribution to reproductive organs, thereby maximizing seed cotton yield, which reached up to 6420.47 kg·ha^-1.