Effects of irrigation termination date on cotton yield and fiber quality

Fiber immaturity decreases profits for many cotton producers on the Texas High Plains. Correct timing of the final irrigation may enhance crop maturity and conserve water. Irrigation termination shortly after physiological cutout may inhibit the production of young fruit and divert additional resources to existing fruit, promoting fiber maturity. The objective of this research was to determine if proper irrigation termination can increase crop maturity rate and improve fiber quality without affecting yield. Studies were conducted for three site-years on sub-surface drip irrigation at Halfway, New Deal, and Lubbock, Texas in 2010 and 2011. Multiple cultivars were grown under three irrigation termination methods: incremental termination at nodes above white flower (NAWF) = 5 + 2 weeks; incremental termination at NAWF = 5 + 4 weeks; and complete irrigation cut-off at NAWF = 5 + 6 weeks. Production and retention of the uppermost flowers and fruit were measured, as well as fiber quality from the harvested plots. In 2010, length was improved with earlier termination at the Halfway location. At the Quaker location, seed yield, lint, turnout, and length improved with later termination, but micronaire became less desirable. In 2011, turnout and micronaire were improved with earlier irrigation termination. When the cost of irrigation was low, the 4 week irrigation treatment was the most profitable in 2010, but as the cost of irrigation reached $10/ha-cm, the Halfway location became more profitable with the 2 week irrigation. In 2011, net income between irrigations was not statistically different.