Doctor of Philosophy (PhD)


Plant, Environmental Management and Soil Sciences

Document Type



Field studies evaluated the effect of plant population and seeding configuration on cotton (Gossypium hirsutum L.) growth and yield. Seeding configuration did not influence plant growth and development parameters. Averaged across seeding configurations, plants grown at a density of 152,833 plants ha-1 were taller than plants grown at 50,958 and 33,975 plants ha-1, and produced fewer mainstem nodes than all other populations. A 4- and 5-day (2003) and 13- and 14-day (2004) delay in peak bloom was associated with populations of 50,958 and 33,975 plants ha-1, respectively, when compared to 152,833 plants ha-1. Lint yield was not significantly reduced until plant population was lowered to 33,975 (30.5 cm plant spacing) or 50,958 (three plants per hill, 60 cm hill spacing) plants ha-1. Fiber properties were not influenced by plant population or seeding configuration. In field experiments conducted at two Louisiana locations, the effect of late-season insect simulated defoliation (manual leaf removal) and premature harvest-aid application on cotton yield and fiber quality was evaluated. Results suggest a negative impact on yield and fiber quality should not occur when terminating management strategies for late-season bottom defoliating insects at plant development ≥ NAWF5 (five nodes above the uppermost first position white flower, i.e. cutout) +550 HU (heat units), while harvest-aid application should not be initiated until plant development exceeds NAWF5+750 HU. Data obtained from field studies conducted in both Louisiana and Tennessee, which evaluated the effect of carrier volume and nozzle type on cotton harvest-aid efficacy, determined that harvest-aids should be applied through flat fan or hollow cone nozzles at carrier volumes of at least 93.5 L ha-1. These applications are necessary to maximize efficacy, by increasing canopy penetration by spray droplets, to achieve adequate defoliation for a once over harvest. Defoliation timing experiments in Louisiana identified 40 to 60 percent open bolls as the stage of crop maturity when harvest-aid application will result in maximum lint yields. However, a second harvest may be necessary to realize maximum lint yield. Delaying defoliation until after 75 percent open bolls may have detrimental effects on fiber quality resulting in discounts and reduced gross revenue.



Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Gerald O. Myers