Plant Density Effects on Variety Specific of Safflower (Carthamus tinctorius L.)

Abstract

Safflower (Carthamus tinctorius L.) is a multipurpose oilseed crop with considerable potential for diversification of oilseed production in semi-arid environments. However, productivity depends strongly on genotype and plant population, which influence canopy architecture, biomass accumulation, yield formation, and assimilate partitioning. This study evaluated the effects of three plant densities (128,571, 257,142, and 385,714 plants ha⁻¹) on the growth, yield components, biomass production, harvest index, and seed quality of two safflower varieties, Dongla and Giza, during two winter growing seasons (2014/15 and 2015/16) in Sudan. Field experiments were conducted at Shambat, Khartoum North, Sudan, using a randomised complete block design with three replications based on split-plot arrangements. Analysis of variance was performed separately for each growing season, and combined means were used to assess overall treatment responses. The varieties exhibited contrasting growth architectures. Giza was consistently taller and developed a greater leaf area, whereas Dongla produced substantially more branches and heads per plant. Relative growth rate, plant height, branch number, and leaf area showed considerable numerical variation among treatments, although treatment effects were not statistically significant. Thousand-seed weight was significantly affected by treatment combinations in the first season and in the combined analysis, with the highest overall value recorded for Giza at 257,142 plants ha⁻¹ (27.7 g). Giza generally produced greater biomass, reaching 10.3 t ha⁻¹ at 385,714 plants ha⁻¹, whereas Dongla achieved the highest combined harvest index (15.5%) at 257,142 plants ha⁻¹. Seed yield ranged from 0.9 to 1.4 t ha⁻¹, with the highest combined mean yield (1.2 t ha⁻¹) recorded for Dongla at 257,142 plants ha⁻¹ and Giza at 385,714 plants ha⁻¹. Seed fat, protein, and crude fibre contents remained stable across treatments. Overall, the results demonstrate the importance of variety-specific plant-density management for optimizing safflower growth, biomass production, and assimilate partitioning under varying Sudanese environmental conditions.