Quantifying potential production risks of technologies nearing commercialization, management practices for cotton irrigation, and leaf pubescence and defoliation strategy influence on cotton defoliation and fiber quality
Byrd, Seth Andrew
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A variety of issues potentially impact cotton production and management of the crop, including new herbicide technologies, concerns over agricultural water use, and managing the crop to maximize yield and fiber quality. Multi-location trials were conducted in Georgia and across the cotton belt to evaluate the impact of sub-lethal rates of 2,4-D on cotton at various growth sages, the potential water savings benefits from a conservation tillage system utilizing a high biomass rolled rye cover crop system in cotton, and the influence of leaf pubescence and defoliation strategy on cotton fiber quality. Growth stages around the early bloom period were determined to be the most sensitive to sub-lethal rates of 2,4-D, primarily due to reductions in the number of bolls produced by damaged plants. Visual injury ratings and measurements of chlorophyll a fluorescence of cotton did not reflect yield loss resulting from 2,4-D exposure. The high biomass rolled rye conservation tillage system resulted in minimal benefits in soil moisture, cotton growth and development, and yield. In two of four locations, plant growth was negatively impacted by the conservation tillage system, while yield was lower in one location due to conservation tillage compared to conventional tillage. It appears that potential benefits gained from this system are highly dependent on environmental conditions, while detriments may be present in years when excessive rainfall occurs during the growing season. Multiple physiological measurements also illustrated minimal impact due to conservation tillage compared to conventional tillage. Varying water supply treatments were included, and typically benefits in cotton growth, development, and yield were observed in treatments that supplied the crop with the two greatest amounts of irrigation. Similar results were observed in physiological parameters, as leaf water potential and stomatal conductance were reduced when cotton received no supplemental irrigation compared to fully irrigated cotton. Minimizing leaf grade and trash content in ginned lint is one method to achieve maximum fiber quality. Trials determined that while a desiccating defoliation strategy can hamper cotton defoliation, leaf pubescence of cultivars is the primary driver behind the amount of leaf and trash content that remains in ginned lint.