Submitted to: Journal of Cotton Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/2/2006
Publication Date: 7/6/2006
Citation: Nuti, R.C., Casteel, S., Viator, R.P., Edmisten, K., Jordan, D., Grabow, G., Lanier, J. Management of cotton (Gossypium hirsutum) grown under overhead sprinkle and sub-surface drip irrigation in North Carolina. Journal of Cotton Science. 10:76-88. Interpretive Summary: In dry regions, irrigation may be used as the only source of water to grow a crop. Irrigation may also be used to supplement natural rainfall for improving crop production in regions typically farmed with rainfed or dryland practices. Use of irrigation usually improves cotton yield. Little research has been done comparing how irrigation water is applied in cotton, especially comparing overhead sprinkle and sub-surface drip application methods. Improving crop growth potential through irrigation may increase the need for plant growth regulator use to reduce unwanted cotton plant growth. Glyphosate is a commonly used herbicide for controlling weeds in glyphosate resistant cotton. Irrigation may affect the way glyphosate resistant cotton responds to glyphosate use. The objectives of this study were to compare overhead sprinkle and sub-surface drip irrigation methods in cotton and determine if cotton response to glyphosate and the plant growth regulator, mepiquat chloride, is different between the two irrigation types. Cotton field trials were conducted in 2001, 2002, and 2003 at the Peanut Belt Research Station in North Carolina. Treatments consisted of overhead sprinkle and sub-surface drip irrigation methods factored over two glyphosate treatment timings at either four-leaf or eight-leaf growth stages. The four-leaf glyphosate treatment was applied broadcast and the eight-leaf application was sprayed post-direct with contact to the bottom third of the plant. The rate of glyphosate was 0.84 kg acid equivalent per hectare. Each of these irrigation and glyphosate combinations were treated with or without mepiquat chloride as directed under North Carolina extension recommendations. Cotton yield comparisons were not the same between irrigation systems each year. Cotton yield was not affected by the use of mepiquat chloride. Glyphosate applied non-precision post-direct reduced yield in one of three years. Cotton fiber was longer when irrigated with sub-surface drip rather than overhead irrigation. Cotton plants were shorter and had fewer nodes when mepiquat chloride was used. Glyphosate applied post-direct reduced maturity in each irrigation system in one of three years. Mepiquat chloride use improved retention of cotton fruit and improved boll maturity.
Technical Abstract: Irrigation systems, whether used to supplement rain-fed systems or being the main source of water for crop use, consistently show positive results in cotton (Gossypium hirsutum) regardless of delivery method. Very little research has been conducted comparing overhead sprinkle (OSI) and sub-surface drip (SSD) irrigation methods in cotton. Providing water by irrigation may affect the need for mepiquat chloride (MC) and how glyphosate resistant cotton responds to glyphosate. The objectives of this study were to compare OSI and SSD irrigation in cotton and determine if cotton response to glyphosate and MC was variable between irrigation systems. Cotton field trials were conducted in 2001, 2002, and 2003 at the Peanut Belt Research Station in North Carolina. Treatments consisted of OSI and SSD irrigation methods factored over glyphosate treatments of 0.84 kg ae ha-1 applied at either four-leaf POST or non-precision PD at eight-leaf. Each of these irrigation and glyphosate combinations were treated with or without MC in a standard program. Lint yield results varied between irrigation systems over years, and were not affected by MC. Non-precision applied glyphosate reduced yield in one of three years. Fiber length was better in SSD than OSI and also improved with MC. Plant height was consistently controlled and node production was reduced when MC was used. Glyphosate applied non-precision reduced maturity in each irrigation system in one of three years. Fruit retention and maturity was increased with MC.