AGRONOMY & SOILS Response of Obsolete and Modern Cotton Genotypes to Varying Plant Densities

Cotton (Gossypium hirsutum L.) producers are interested in reduced seeding rates due to increasing seed costs. It is not clear whether diverse cotton genotypes respond differently to reduced plant densities. The objectives of this research were to evaluate the performance of obsolete and modern cotton genotypes grown under reduced and traditional plant population densities. The six genotypes representing five decades of release were grown at either five plants m -2 (low) or 10 plants m -2 (high) densities, during the years 2009 through 2012. Dry-matter partitioning, growth analysis, yield, yield component, and fiber quality data were collected. Genotypes did not interact with plant densities for any trait. Despite few consistent dry-matter partitioning or growth differences among the genotypes, large genotypic differences were detected in lint yield and fiber quality production. The obsolete genotypes had lower yields because of reduced lint percentage and lint index. The higher yielding genotypes produced more bolls per unit area to generate their higher yields. Increased light interception by the high density treatment was offset by the ability of the leaves of the low density canopy to more efficiently intercept and utilize sunlight. These counteracting traits resulted in no yield or fiber quality differences between the two densities. Yield success can be achieved with a reduced seeding rate if uniform seedling spacing is also achieved, possibly regardless of the cultivar planted.