Effects of Irrigation Termination Date on Cotton Yield and Fiber Quality

One of the biggest problems facing cotton production on the Texas High Plains is fiber immaturity.  Correct timing of the final irrigation in cotton may not only enhance crop maturity, but conserve water as well.  It is suggested that irrigation termination shortly after physiological cutout may inhibit further vegetative growth, cause abscission of young fruit, divert additional resources to existing fruit, changing fiber maturity.  The objective of this research was to determine if proper irrigation termination will increase crop maturity rate and improve fiber quality without affecting yield. Studies were conducted at the Texas AgriLife Research Center in Halfway and the Texas Tech University Quaker Avenue Research Farm in field sites with sub surface drip irrigation in 2010 and 2011.  Nine zones of the sub surface drip irrigation system at each location were used. The main plot treatments were timing of irrigation termination and the sub plot treatments were cultivar.  Irrigation was terminated at Nodes above white flower (NAWF) = 5 + 2 weeks, NAWF = 5 + 4 weeks, and NAWF = 5 + 6 weeks.  Soil water status was  monitored with a neutron moisture meter.  Fiber samples were analyzed at the Texas Tech Fiber and Biopolymer Research Institute for AFIS, HVI, and minispinning analyses.  Staple and micronaire were significantly different among irrigation treatments at one location in 2010, while strength showed no response to irrigation at either location.  Response to irrigation was significantly different among cultivars at each location in 2010. At Halfway, 5.22” water was saved using the NAWF 5 + 2 weeks mark for irrigation termination, and strength and micronaire would only be slightly affected. At the Texas Tech Quaker Farm, NAWF 5 + 4 weeks was the best mark for this particular year.  A little less than one acre inch (.88”) of water could have been saved, while only slightly affecting strength and micronaire.